Source file src/cmd/go/internal/modload/init.go

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package modload
     6  
     7  import (
     8  	"bytes"
     9  	"context"
    10  	"errors"
    11  	"fmt"
    12  	"internal/godebugs"
    13  	"internal/lazyregexp"
    14  	"io"
    15  	"maps"
    16  	"os"
    17  	"path"
    18  	"path/filepath"
    19  	"slices"
    20  	"strconv"
    21  	"strings"
    22  	"sync"
    23  
    24  	"cmd/go/internal/base"
    25  	"cmd/go/internal/cfg"
    26  	"cmd/go/internal/fips140"
    27  	"cmd/go/internal/fsys"
    28  	"cmd/go/internal/gover"
    29  	"cmd/go/internal/lockedfile"
    30  	"cmd/go/internal/modfetch"
    31  	"cmd/go/internal/search"
    32  
    33  	"golang.org/x/mod/modfile"
    34  	"golang.org/x/mod/module"
    35  )
    36  
    37  // Variables set by other packages.
    38  //
    39  // TODO(#40775): See if these can be plumbed as explicit parameters.
    40  var (
    41  	// ExplicitWriteGoMod prevents LoadPackages, ListModules, and other functions
    42  	// from updating go.mod and go.sum or reporting errors when updates are
    43  	// needed. A package should set this if it would cause go.mod to be written
    44  	// multiple times (for example, 'go get' calls LoadPackages multiple times) or
    45  	// if it needs some other operation to be successful before go.mod and go.sum
    46  	// can be written (for example, 'go mod download' must download modules before
    47  	// adding sums to go.sum). Packages that set this are responsible for calling
    48  	// WriteGoMod explicitly.
    49  	ExplicitWriteGoMod bool
    50  )
    51  
    52  // Variables set in Init.
    53  var (
    54  	gopath string
    55  )
    56  
    57  // EnterModule resets MainModules and requirements to refer to just this one module.
    58  func EnterModule(loaderstate *State, ctx context.Context, enterModroot string) {
    59  	loaderstate.MainModules = nil // reset MainModules
    60  	loaderstate.requirements = nil
    61  	loaderstate.workFilePath = "" // Force module mode
    62  	loaderstate.Fetcher().Reset()
    63  
    64  	loaderstate.modRoots = []string{enterModroot}
    65  	LoadModFile(loaderstate, ctx)
    66  }
    67  
    68  // EnterWorkspace enters workspace mode from module mode, applying the updated requirements to the main
    69  // module to that module in the workspace. There should be no calls to any of the exported
    70  // functions of the modload package running concurrently with a call to EnterWorkspace as
    71  // EnterWorkspace will modify the global state they depend on in a non-thread-safe way.
    72  func EnterWorkspace(loaderstate *State, ctx context.Context) (exit func(), err error) {
    73  	// Find the identity of the main module that will be updated before we reset modload state.
    74  	mm := loaderstate.MainModules.mustGetSingleMainModule(loaderstate)
    75  	// Get the updated modfile we will use for that module.
    76  	_, _, updatedmodfile, err := UpdateGoModFromReqs(loaderstate, ctx, WriteOpts{})
    77  	if err != nil {
    78  		return nil, err
    79  	}
    80  
    81  	// Reset the state to a clean state.
    82  	oldstate := loaderstate.setState(NewState())
    83  	loaderstate.ForceUseModules = true
    84  
    85  	// Load in workspace mode.
    86  	loaderstate.InitWorkfile()
    87  	LoadModFile(loaderstate, ctx)
    88  
    89  	// Update the content of the previous main module, and recompute the requirements.
    90  	*loaderstate.MainModules.ModFile(mm) = *updatedmodfile
    91  	loaderstate.requirements = requirementsFromModFiles(loaderstate, ctx, loaderstate.MainModules.workFile, slices.Collect(maps.Values(loaderstate.MainModules.modFiles)), nil)
    92  
    93  	return func() {
    94  		loaderstate.setState(oldstate)
    95  	}, nil
    96  }
    97  
    98  type MainModuleSet struct {
    99  	// versions are the module.Version values of each of the main modules.
   100  	// For each of them, the Path fields are ordinary module paths and the Version
   101  	// fields are empty strings.
   102  	// versions is clipped (len=cap).
   103  	versions []module.Version
   104  
   105  	// modRoot maps each module in versions to its absolute filesystem path.
   106  	modRoot map[module.Version]string
   107  
   108  	// pathPrefix is the path prefix for packages in the module, without a trailing
   109  	// slash. For most modules, pathPrefix is just version.Path, but the
   110  	// standard-library module "std" has an empty prefix.
   111  	pathPrefix map[module.Version]string
   112  
   113  	// inGorootSrc caches whether modRoot is within GOROOT/src.
   114  	// The "std" module is special within GOROOT/src, but not otherwise.
   115  	inGorootSrc map[module.Version]bool
   116  
   117  	modFiles map[module.Version]*modfile.File
   118  
   119  	tools map[string]bool
   120  
   121  	modContainingCWD module.Version
   122  
   123  	workFile *modfile.WorkFile
   124  
   125  	workFileReplaceMap map[module.Version]module.Version
   126  	// highest replaced version of each module path; empty string for wildcard-only replacements
   127  	highestReplaced map[string]string
   128  
   129  	indexMu sync.RWMutex
   130  	indices map[module.Version]*modFileIndex
   131  }
   132  
   133  func (mms *MainModuleSet) PathPrefix(m module.Version) string {
   134  	return mms.pathPrefix[m]
   135  }
   136  
   137  // Versions returns the module.Version values of each of the main modules.
   138  // For each of them, the Path fields are ordinary module paths and the Version
   139  // fields are empty strings.
   140  // Callers should not modify the returned slice.
   141  func (mms *MainModuleSet) Versions() []module.Version {
   142  	if mms == nil {
   143  		return nil
   144  	}
   145  	return mms.versions
   146  }
   147  
   148  // Tools returns the tools defined by all the main modules.
   149  // The key is the absolute package path of the tool.
   150  func (mms *MainModuleSet) Tools() map[string]bool {
   151  	if mms == nil {
   152  		return nil
   153  	}
   154  	return mms.tools
   155  }
   156  
   157  func (mms *MainModuleSet) Contains(path string) bool {
   158  	if mms == nil {
   159  		return false
   160  	}
   161  	for _, v := range mms.versions {
   162  		if v.Path == path {
   163  			return true
   164  		}
   165  	}
   166  	return false
   167  }
   168  
   169  func (mms *MainModuleSet) ModRoot(m module.Version) string {
   170  	if mms == nil {
   171  		return ""
   172  	}
   173  	return mms.modRoot[m]
   174  }
   175  
   176  func (mms *MainModuleSet) InGorootSrc(m module.Version) bool {
   177  	if mms == nil {
   178  		return false
   179  	}
   180  	return mms.inGorootSrc[m]
   181  }
   182  
   183  func (mms *MainModuleSet) mustGetSingleMainModule(loaderstate *State) module.Version {
   184  	mm, err := mms.getSingleMainModule(loaderstate)
   185  	if err != nil {
   186  		panic(err)
   187  	}
   188  	return mm
   189  }
   190  
   191  func (mms *MainModuleSet) getSingleMainModule(loaderstate *State) (module.Version, error) {
   192  	if mms == nil || len(mms.versions) == 0 {
   193  		return module.Version{}, errors.New("internal error: mustGetSingleMainModule called in context with no main modules")
   194  	}
   195  	if len(mms.versions) != 1 {
   196  		if loaderstate.inWorkspaceMode() {
   197  			return module.Version{}, errors.New("internal error: mustGetSingleMainModule called in workspace mode")
   198  		} else {
   199  			return module.Version{}, errors.New("internal error: multiple main modules present outside of workspace mode")
   200  		}
   201  	}
   202  	return mms.versions[0], nil
   203  }
   204  
   205  func (mms *MainModuleSet) GetSingleIndexOrNil(loaderstate *State) *modFileIndex {
   206  	if mms == nil {
   207  		return nil
   208  	}
   209  	if len(mms.versions) == 0 {
   210  		return nil
   211  	}
   212  	return mms.indices[mms.mustGetSingleMainModule(loaderstate)]
   213  }
   214  
   215  func (mms *MainModuleSet) Index(m module.Version) *modFileIndex {
   216  	mms.indexMu.RLock()
   217  	defer mms.indexMu.RUnlock()
   218  	return mms.indices[m]
   219  }
   220  
   221  func (mms *MainModuleSet) SetIndex(m module.Version, index *modFileIndex) {
   222  	mms.indexMu.Lock()
   223  	defer mms.indexMu.Unlock()
   224  	mms.indices[m] = index
   225  }
   226  
   227  func (mms *MainModuleSet) ModFile(m module.Version) *modfile.File {
   228  	return mms.modFiles[m]
   229  }
   230  
   231  func (mms *MainModuleSet) WorkFile() *modfile.WorkFile {
   232  	return mms.workFile
   233  }
   234  
   235  func (mms *MainModuleSet) Len() int {
   236  	if mms == nil {
   237  		return 0
   238  	}
   239  	return len(mms.versions)
   240  }
   241  
   242  // ModContainingCWD returns the main module containing the working directory,
   243  // or module.Version{} if none of the main modules contain the working
   244  // directory.
   245  func (mms *MainModuleSet) ModContainingCWD() module.Version {
   246  	return mms.modContainingCWD
   247  }
   248  
   249  func (mms *MainModuleSet) HighestReplaced() map[string]string {
   250  	return mms.highestReplaced
   251  }
   252  
   253  // GoVersion returns the go version set on the single module, in module mode,
   254  // or the go.work file in workspace mode.
   255  func (mms *MainModuleSet) GoVersion(loaderstate *State) string {
   256  	if loaderstate.inWorkspaceMode() {
   257  		return gover.FromGoWork(mms.workFile)
   258  	}
   259  	if mms != nil && len(mms.versions) == 1 {
   260  		f := mms.ModFile(mms.mustGetSingleMainModule(loaderstate))
   261  		if f == nil {
   262  			// Special case: we are outside a module, like 'go run x.go'.
   263  			// Assume the local Go version.
   264  			// TODO(#49228): Clean this up; see loadModFile.
   265  			return gover.Local()
   266  		}
   267  		return gover.FromGoMod(f)
   268  	}
   269  	return gover.DefaultGoModVersion
   270  }
   271  
   272  // Godebugs returns the godebug lines set on the single module, in module mode,
   273  // or on the go.work file in workspace mode.
   274  // The caller must not modify the result.
   275  func (mms *MainModuleSet) Godebugs(loaderstate *State) []*modfile.Godebug {
   276  	if loaderstate.inWorkspaceMode() {
   277  		if mms.workFile != nil {
   278  			return mms.workFile.Godebug
   279  		}
   280  		return nil
   281  	}
   282  	if mms != nil && len(mms.versions) == 1 {
   283  		f := mms.ModFile(mms.mustGetSingleMainModule(loaderstate))
   284  		if f == nil {
   285  			// Special case: we are outside a module, like 'go run x.go'.
   286  			return nil
   287  		}
   288  		return f.Godebug
   289  	}
   290  	return nil
   291  }
   292  
   293  func (mms *MainModuleSet) WorkFileReplaceMap() map[module.Version]module.Version {
   294  	return mms.workFileReplaceMap
   295  }
   296  
   297  type Root int
   298  
   299  const (
   300  	// AutoRoot is the default for most commands. modload.Init will look for
   301  	// a go.mod file in the current directory or any parent. If none is found,
   302  	// modules may be disabled (GO111MODULE=auto) or commands may run in a
   303  	// limited module mode.
   304  	AutoRoot Root = iota
   305  
   306  	// NoRoot is used for commands that run in module mode and ignore any go.mod
   307  	// file the current directory or in parent directories.
   308  	NoRoot
   309  
   310  	// NeedRoot is used for commands that must run in module mode and don't
   311  	// make sense without a main module.
   312  	NeedRoot
   313  )
   314  
   315  // ModFile returns the parsed go.mod file.
   316  //
   317  // Note that after calling LoadPackages or LoadModGraph,
   318  // the require statements in the modfile.File are no longer
   319  // the source of truth and will be ignored: edits made directly
   320  // will be lost at the next call to WriteGoMod.
   321  // To make permanent changes to the require statements
   322  // in go.mod, edit it before loading.
   323  func ModFile(loaderstate *State) *modfile.File {
   324  	Init(loaderstate)
   325  	modFile := loaderstate.MainModules.ModFile(loaderstate.MainModules.mustGetSingleMainModule(loaderstate))
   326  	if modFile == nil {
   327  		die(loaderstate)
   328  	}
   329  	return modFile
   330  }
   331  
   332  func BinDir(loaderstate *State) string {
   333  	Init(loaderstate)
   334  	if cfg.GOBIN != "" {
   335  		return cfg.GOBIN
   336  	}
   337  	if gopath == "" {
   338  		return ""
   339  	}
   340  	return filepath.Join(gopath, "bin")
   341  }
   342  
   343  // InitWorkfile initializes the workFilePath variable for commands that
   344  // operate in workspace mode. It should not be called by other commands,
   345  // for example 'go mod tidy', that don't operate in workspace mode.
   346  func (loaderstate *State) InitWorkfile() {
   347  	// Initialize fsys early because we need overlay to read go.work file.
   348  	fips140.Init()
   349  	if err := fsys.Init(); err != nil {
   350  		base.Fatal(err)
   351  	}
   352  	loaderstate.workFilePath = loaderstate.FindGoWork(base.Cwd())
   353  }
   354  
   355  // FindGoWork returns the name of the go.work file for this command,
   356  // or the empty string if there isn't one.
   357  // Most code should use Init and Enabled rather than use this directly.
   358  // It is exported mainly for Go toolchain switching, which must process
   359  // the go.work very early at startup.
   360  func (loaderstate *State) FindGoWork(wd string) string {
   361  	if loaderstate.RootMode == NoRoot {
   362  		return ""
   363  	}
   364  
   365  	switch gowork := cfg.Getenv("GOWORK"); gowork {
   366  	case "off":
   367  		return ""
   368  	case "", "auto":
   369  		return findWorkspaceFile(wd)
   370  	default:
   371  		if !filepath.IsAbs(gowork) {
   372  			base.Fatalf("go: invalid GOWORK: not an absolute path")
   373  		}
   374  		return gowork
   375  	}
   376  }
   377  
   378  // WorkFilePath returns the absolute path of the go.work file, or "" if not in
   379  // workspace mode. WorkFilePath must be called after InitWorkfile.
   380  func WorkFilePath(loaderstate *State) string {
   381  	return loaderstate.workFilePath
   382  }
   383  
   384  // Reset clears all the initialized, cached state about the use of modules,
   385  // so that we can start over.
   386  func (s *State) Reset() {
   387  	s.setState(NewState())
   388  }
   389  
   390  func (s *State) setState(new *State) (old *State) {
   391  	old = &State{
   392  		initialized:     s.initialized,
   393  		ForceUseModules: s.ForceUseModules,
   394  		RootMode:        s.RootMode,
   395  		modRoots:        s.modRoots,
   396  		modulesEnabled:  cfg.ModulesEnabled,
   397  		MainModules:     s.MainModules,
   398  		requirements:    s.requirements,
   399  		workFilePath:    s.workFilePath,
   400  		fetcher:         s.fetcher,
   401  	}
   402  	s.initialized = new.initialized
   403  	s.ForceUseModules = new.ForceUseModules
   404  	s.RootMode = new.RootMode
   405  	s.modRoots = new.modRoots
   406  	cfg.ModulesEnabled = new.modulesEnabled
   407  	s.MainModules = new.MainModules
   408  	s.requirements = new.requirements
   409  	s.workFilePath = new.workFilePath
   410  	// The modfetch package's global state is used to compute
   411  	// the go.sum file, so save and restore it along with the
   412  	// modload state.
   413  	old.fetcher = s.fetcher.SetState(new.fetcher)
   414  
   415  	return old
   416  }
   417  
   418  type State struct {
   419  	initialized               bool
   420  	allowMissingModuleImports bool
   421  
   422  	// ForceUseModules may be set to force modules to be enabled when
   423  	// GO111MODULE=auto or to report an error when GO111MODULE=off.
   424  	ForceUseModules bool
   425  
   426  	// RootMode determines whether a module root is needed.
   427  	RootMode Root
   428  
   429  	// These are primarily used to initialize the MainModules, and should
   430  	// be eventually superseded by them but are still used in cases where
   431  	// the module roots are required but MainModules has not been
   432  	// initialized yet. Set to the modRoots of the main modules.
   433  	// modRoots != nil implies len(modRoots) > 0
   434  	modRoots       []string
   435  	modulesEnabled bool
   436  	MainModules    *MainModuleSet
   437  
   438  	// pkgLoader is the most recently-used package loader.
   439  	// It holds details about individual packages.
   440  	//
   441  	// This variable should only be accessed directly in top-level exported
   442  	// functions. All other functions that require or produce a *packageLoader should pass
   443  	// or return it as an explicit parameter.
   444  	pkgLoader *packageLoader
   445  
   446  	// requirements is the requirement graph for the main module.
   447  	//
   448  	// It is always non-nil if the main module's go.mod file has been
   449  	// loaded.
   450  	//
   451  	// This variable should only be read from the loadModFile
   452  	// function, and should only be written in the loadModFile and
   453  	// commitRequirements functions.  All other functions that need or
   454  	// produce a *Requirements should accept and/or return an explicit
   455  	// parameter.
   456  	requirements *Requirements
   457  
   458  	// Set to the path to the go.work file, or "" if workspace mode is
   459  	// disabled
   460  	workFilePath string
   461  	fetcher      *modfetch.Fetcher
   462  }
   463  
   464  func NewState() *State {
   465  	s := new(State)
   466  	s.fetcher = modfetch.NewFetcher()
   467  	return s
   468  }
   469  
   470  func DisabledState() *State {
   471  	fips140.Init()
   472  	return &State{initialized: true, modulesEnabled: false}
   473  }
   474  
   475  func (s *State) Fetcher() *modfetch.Fetcher {
   476  	return s.fetcher
   477  }
   478  
   479  // Init determines whether module mode is enabled, locates the root of the
   480  // current module (if any), sets environment variables for Git subprocesses, and
   481  // configures the cfg, codehost, load, modfetch, and search packages for use
   482  // with modules.
   483  func Init(loaderstate *State) {
   484  	if loaderstate.initialized {
   485  		return
   486  	}
   487  	loaderstate.initialized = true
   488  
   489  	fips140.Init()
   490  
   491  	// Keep in sync with WillBeEnabled. We perform extra validation here, and
   492  	// there are lots of diagnostics and side effects, so we can't use
   493  	// WillBeEnabled directly.
   494  	var mustUseModules bool
   495  	env := cfg.Getenv("GO111MODULE")
   496  	switch env {
   497  	default:
   498  		base.Fatalf("go: unknown environment setting GO111MODULE=%s", env)
   499  	case "auto":
   500  		mustUseModules = loaderstate.ForceUseModules
   501  	case "on", "":
   502  		mustUseModules = true
   503  	case "off":
   504  		if loaderstate.ForceUseModules {
   505  			base.Fatalf("go: modules disabled by GO111MODULE=off; see 'go help modules'")
   506  		}
   507  		mustUseModules = false
   508  		return
   509  	}
   510  
   511  	if err := fsys.Init(); err != nil {
   512  		base.Fatal(err)
   513  	}
   514  
   515  	// Disable any prompting for passwords by Git.
   516  	// Only has an effect for 2.3.0 or later, but avoiding
   517  	// the prompt in earlier versions is just too hard.
   518  	// If user has explicitly set GIT_TERMINAL_PROMPT=1, keep
   519  	// prompting.
   520  	// See golang.org/issue/9341 and golang.org/issue/12706.
   521  	if os.Getenv("GIT_TERMINAL_PROMPT") == "" {
   522  		os.Setenv("GIT_TERMINAL_PROMPT", "0")
   523  	}
   524  
   525  	if os.Getenv("GCM_INTERACTIVE") == "" {
   526  		os.Setenv("GCM_INTERACTIVE", "never")
   527  	}
   528  	if loaderstate.modRoots != nil {
   529  		// modRoot set before Init was called ("go mod init" does this).
   530  		// No need to search for go.mod.
   531  	} else if loaderstate.RootMode == NoRoot {
   532  		if cfg.ModFile != "" && !base.InGOFLAGS("-modfile") {
   533  			base.Fatalf("go: -modfile cannot be used with commands that ignore the current module")
   534  		}
   535  		loaderstate.modRoots = nil
   536  	} else if loaderstate.workFilePath != "" {
   537  		// We're in workspace mode, which implies module mode.
   538  		if cfg.ModFile != "" {
   539  			base.Fatalf("go: -modfile cannot be used in workspace mode")
   540  		}
   541  	} else {
   542  		if modRoot := findModuleRoot(base.Cwd()); modRoot == "" {
   543  			if cfg.ModFile != "" {
   544  				base.Fatalf("go: cannot find main module, but -modfile was set.\n\t-modfile cannot be used to set the module root directory.")
   545  			}
   546  			if loaderstate.RootMode == NeedRoot {
   547  				base.Fatal(NewNoMainModulesError(loaderstate))
   548  			}
   549  			if !mustUseModules {
   550  				// GO111MODULE is 'auto', and we can't find a module root.
   551  				// Stay in GOPATH mode.
   552  				return
   553  			}
   554  		} else if search.InDir(modRoot, os.TempDir()) == "." {
   555  			// If you create /tmp/go.mod for experimenting,
   556  			// then any tests that create work directories under /tmp
   557  			// will find it and get modules when they're not expecting them.
   558  			// It's a bit of a peculiar thing to disallow but quite mysterious
   559  			// when it happens. See golang.org/issue/26708.
   560  			fmt.Fprintf(os.Stderr, "go: warning: ignoring go.mod in system temp root %v\n", os.TempDir())
   561  			if loaderstate.RootMode == NeedRoot {
   562  				base.Fatal(NewNoMainModulesError(loaderstate))
   563  			}
   564  			if !mustUseModules {
   565  				return
   566  			}
   567  		} else {
   568  			loaderstate.modRoots = []string{modRoot}
   569  		}
   570  	}
   571  	if cfg.ModFile != "" && !strings.HasSuffix(cfg.ModFile, ".mod") {
   572  		base.Fatalf("go: -modfile=%s: file does not have .mod extension", cfg.ModFile)
   573  	}
   574  
   575  	// We're in module mode. Set any global variables that need to be set.
   576  	cfg.ModulesEnabled = true
   577  	setDefaultBuildMod(loaderstate)
   578  	list := filepath.SplitList(cfg.BuildContext.GOPATH)
   579  	if len(list) > 0 && list[0] != "" {
   580  		gopath = list[0]
   581  		if _, err := fsys.Stat(filepath.Join(gopath, "go.mod")); err == nil {
   582  			fmt.Fprintf(os.Stderr, "go: warning: ignoring go.mod in $GOPATH %v\n", gopath)
   583  			if loaderstate.RootMode == NeedRoot {
   584  				base.Fatal(NewNoMainModulesError(loaderstate))
   585  			}
   586  			if !mustUseModules {
   587  				return
   588  			}
   589  		}
   590  	}
   591  }
   592  
   593  // WillBeEnabled checks whether modules should be enabled but does not
   594  // initialize modules by installing hooks. If Init has already been called,
   595  // WillBeEnabled returns the same result as Enabled.
   596  //
   597  // This function is needed to break a cycle. The main package needs to know
   598  // whether modules are enabled in order to install the module or GOPATH version
   599  // of 'go get', but Init reads the -modfile flag in 'go get', so it shouldn't
   600  // be called until the command is installed and flags are parsed. Instead of
   601  // calling Init and Enabled, the main package can call this function.
   602  func (loaderstate *State) WillBeEnabled() bool {
   603  	if loaderstate.modRoots != nil || cfg.ModulesEnabled {
   604  		// Already enabled.
   605  		return true
   606  	}
   607  	if loaderstate.initialized {
   608  		// Initialized, not enabled.
   609  		return false
   610  	}
   611  
   612  	// Keep in sync with Init. Init does extra validation and prints warnings or
   613  	// exits, so it can't call this function directly.
   614  	env := cfg.Getenv("GO111MODULE")
   615  	switch env {
   616  	case "on", "":
   617  		return true
   618  	case "auto":
   619  		break
   620  	default:
   621  		return false
   622  	}
   623  
   624  	return FindGoMod(base.Cwd()) != "" || loaderstate.FindGoWork(base.Cwd()) != ""
   625  }
   626  
   627  // FindGoMod returns the name of the go.mod file for this command,
   628  // or the empty string if there isn't one.
   629  // Most code should use Init and Enabled rather than use this directly.
   630  // It is exported mainly for Go toolchain switching, which must process
   631  // the go.mod very early at startup.
   632  func FindGoMod(wd string) string {
   633  	modRoot := findModuleRoot(wd)
   634  	if modRoot == "" {
   635  		// GO111MODULE is 'auto', and we can't find a module root.
   636  		// Stay in GOPATH mode.
   637  		return ""
   638  	}
   639  	if search.InDir(modRoot, os.TempDir()) == "." {
   640  		// If you create /tmp/go.mod for experimenting,
   641  		// then any tests that create work directories under /tmp
   642  		// will find it and get modules when they're not expecting them.
   643  		// It's a bit of a peculiar thing to disallow but quite mysterious
   644  		// when it happens. See golang.org/issue/26708.
   645  		return ""
   646  	}
   647  	return filepath.Join(modRoot, "go.mod")
   648  }
   649  
   650  // Enabled reports whether modules are (or must be) enabled.
   651  // If modules are enabled but there is no main module, Enabled returns true
   652  // and then the first use of module information will call die
   653  // (usually through MustModRoot).
   654  func (loaderstate *State) Enabled() bool {
   655  	Init(loaderstate)
   656  	return loaderstate.modRoots != nil || cfg.ModulesEnabled
   657  }
   658  
   659  func (s *State) vendorDir() (string, error) {
   660  	if s.inWorkspaceMode() {
   661  		return filepath.Join(filepath.Dir(WorkFilePath(s)), "vendor"), nil
   662  	}
   663  	mainModule, err := s.MainModules.getSingleMainModule(s)
   664  	if err != nil {
   665  		return "", err
   666  	}
   667  	// Even if -mod=vendor, we could be operating with no mod root (and thus no
   668  	// vendor directory). As long as there are no dependencies that is expected
   669  	// to work. See script/vendor_outside_module.txt.
   670  	modRoot := s.MainModules.ModRoot(mainModule)
   671  	if modRoot == "" {
   672  		return "", errors.New("vendor directory does not exist when in single module mode outside of a module")
   673  	}
   674  	return filepath.Join(modRoot, "vendor"), nil
   675  }
   676  
   677  func (s *State) VendorDirOrEmpty() string {
   678  	dir, err := s.vendorDir()
   679  	if err != nil {
   680  		return ""
   681  	}
   682  	return dir
   683  }
   684  
   685  func VendorDir(loaderstate *State) string {
   686  	dir, err := loaderstate.vendorDir()
   687  	if err != nil {
   688  		panic(err)
   689  	}
   690  	return dir
   691  }
   692  
   693  func (loaderstate *State) inWorkspaceMode() bool {
   694  	if !loaderstate.initialized {
   695  		panic("inWorkspaceMode called before modload.Init called")
   696  	}
   697  	if !loaderstate.Enabled() {
   698  		return false
   699  	}
   700  	return loaderstate.workFilePath != ""
   701  }
   702  
   703  // HasModRoot reports whether a main module or main modules are present.
   704  // HasModRoot may return false even if Enabled returns true: for example, 'get'
   705  // does not require a main module.
   706  func (loaderstate *State) HasModRoot() bool {
   707  	Init(loaderstate)
   708  	return loaderstate.modRoots != nil
   709  }
   710  
   711  // MustHaveModRoot checks that a main module or main modules are present,
   712  // and calls base.Fatalf if there are no main modules.
   713  func (loaderstate *State) MustHaveModRoot() {
   714  	Init(loaderstate)
   715  	if !loaderstate.HasModRoot() {
   716  		die(loaderstate)
   717  	}
   718  }
   719  
   720  // ModFilePath returns the path that would be used for the go.mod
   721  // file, if in module mode. ModFilePath calls base.Fatalf if there is no main
   722  // module, even if -modfile is set.
   723  func (loaderstate *State) ModFilePath() string {
   724  	loaderstate.MustHaveModRoot()
   725  	return modFilePath(findModuleRoot(base.Cwd()))
   726  }
   727  
   728  func modFilePath(modRoot string) string {
   729  	// TODO(matloob): This seems incompatible with workspaces
   730  	// (unless the user's intention is to replace all workspace modules' modfiles?).
   731  	// Should we produce an error in workspace mode if cfg.ModFile is set?
   732  	if cfg.ModFile != "" {
   733  		return cfg.ModFile
   734  	}
   735  	return filepath.Join(modRoot, "go.mod")
   736  }
   737  
   738  func die(loaderstate *State) {
   739  	if cfg.Getenv("GO111MODULE") == "off" {
   740  		base.Fatalf("go: modules disabled by GO111MODULE=off; see 'go help modules'")
   741  	}
   742  	if !loaderstate.inWorkspaceMode() {
   743  		if dir, name := findAltConfig(base.Cwd()); dir != "" {
   744  			rel, err := filepath.Rel(base.Cwd(), dir)
   745  			if err != nil {
   746  				rel = dir
   747  			}
   748  			cdCmd := ""
   749  			if rel != "." {
   750  				cdCmd = fmt.Sprintf("cd %s && ", rel)
   751  			}
   752  			base.Fatalf("go: cannot find main module, but found %s in %s\n\tto create a module there, run:\n\t%sgo mod init", name, dir, cdCmd)
   753  		}
   754  	}
   755  	base.Fatal(NewNoMainModulesError(loaderstate))
   756  }
   757  
   758  var ErrNoModRoot = errors.New("no module root")
   759  
   760  // noMainModulesError returns the appropriate error if there is no main module or
   761  // main modules depending on whether the go command is in workspace mode.
   762  type noMainModulesError struct {
   763  	inWorkspaceMode bool
   764  }
   765  
   766  func (e noMainModulesError) Error() string {
   767  	if e.inWorkspaceMode {
   768  		return "no modules were found in the current workspace; see 'go help work'"
   769  	}
   770  	return "go.mod file not found in current directory or any parent directory; see 'go help modules'"
   771  }
   772  
   773  func (e noMainModulesError) Unwrap() error {
   774  	return ErrNoModRoot
   775  }
   776  
   777  func NewNoMainModulesError(s *State) noMainModulesError {
   778  	return noMainModulesError{
   779  		inWorkspaceMode: s.inWorkspaceMode(),
   780  	}
   781  }
   782  
   783  type goModDirtyError struct{}
   784  
   785  func (goModDirtyError) Error() string {
   786  	if cfg.BuildModExplicit {
   787  		return fmt.Sprintf("updates to go.mod needed, disabled by -mod=%v; to update it:\n\tgo mod tidy", cfg.BuildMod)
   788  	}
   789  	if cfg.BuildModReason != "" {
   790  		return fmt.Sprintf("updates to go.mod needed, disabled by -mod=%s\n\t(%s)\n\tto update it:\n\tgo mod tidy", cfg.BuildMod, cfg.BuildModReason)
   791  	}
   792  	return "updates to go.mod needed; to update it:\n\tgo mod tidy"
   793  }
   794  
   795  var errGoModDirty error = goModDirtyError{}
   796  
   797  // LoadWorkFile parses and checks the go.work file at the given path,
   798  // and returns the absolute paths of the workspace modules' modroots.
   799  // It does not modify the global state of the modload package.
   800  func LoadWorkFile(path string) (workFile *modfile.WorkFile, modRoots []string, err error) {
   801  	workDir := filepath.Dir(path)
   802  	wf, err := ReadWorkFile(path)
   803  	if err != nil {
   804  		return nil, nil, err
   805  	}
   806  	seen := map[string]bool{}
   807  	for _, d := range wf.Use {
   808  		modRoot := d.Path
   809  		if !filepath.IsAbs(modRoot) {
   810  			modRoot = filepath.Join(workDir, modRoot)
   811  		}
   812  
   813  		if seen[modRoot] {
   814  			return nil, nil, fmt.Errorf("error loading go.work:\n%s:%d: path %s appears multiple times in workspace", base.ShortPath(path), d.Syntax.Start.Line, modRoot)
   815  		}
   816  		seen[modRoot] = true
   817  		modRoots = append(modRoots, modRoot)
   818  	}
   819  
   820  	for _, g := range wf.Godebug {
   821  		if err := CheckGodebug("godebug", g.Key, g.Value); err != nil {
   822  			return nil, nil, fmt.Errorf("error loading go.work:\n%s:%d: %w", base.ShortPath(path), g.Syntax.Start.Line, err)
   823  		}
   824  	}
   825  
   826  	return wf, modRoots, nil
   827  }
   828  
   829  // ReadWorkFile reads and parses the go.work file at the given path.
   830  func ReadWorkFile(path string) (*modfile.WorkFile, error) {
   831  	path = base.ShortPath(path) // use short path in any errors
   832  	workData, err := fsys.ReadFile(path)
   833  	if err != nil {
   834  		return nil, fmt.Errorf("reading go.work: %w", err)
   835  	}
   836  
   837  	f, err := modfile.ParseWork(path, workData, nil)
   838  	if err != nil {
   839  		return nil, fmt.Errorf("errors parsing go.work:\n%w", err)
   840  	}
   841  	if f.Go != nil && gover.Compare(f.Go.Version, gover.Local()) > 0 && cfg.CmdName != "work edit" {
   842  		base.Fatal(&gover.TooNewError{What: base.ShortPath(path), GoVersion: f.Go.Version})
   843  	}
   844  	return f, nil
   845  }
   846  
   847  // WriteWorkFile cleans and writes out the go.work file to the given path.
   848  func WriteWorkFile(path string, wf *modfile.WorkFile) error {
   849  	wf.SortBlocks()
   850  	wf.Cleanup()
   851  	out := modfile.Format(wf.Syntax)
   852  
   853  	return os.WriteFile(path, out, 0666)
   854  }
   855  
   856  // UpdateWorkGoVersion updates the go line in wf to be at least goVers,
   857  // reporting whether it changed the file.
   858  func UpdateWorkGoVersion(wf *modfile.WorkFile, goVers string) (changed bool) {
   859  	old := gover.FromGoWork(wf)
   860  	if gover.Compare(old, goVers) >= 0 {
   861  		return false
   862  	}
   863  
   864  	wf.AddGoStmt(goVers)
   865  
   866  	if wf.Toolchain == nil {
   867  		return true
   868  	}
   869  
   870  	// Drop the toolchain line if it is implied by the go line,
   871  	// if its version is older than the version in the go line,
   872  	// or if it is asking for a toolchain older than Go 1.21,
   873  	// which will not understand the toolchain line.
   874  	// Previously, a toolchain line set to the local toolchain
   875  	// version was added so that future operations on the go file
   876  	// would use the same toolchain logic for reproducibility.
   877  	// This behavior seemed to cause user confusion without much
   878  	// benefit so it was removed. See #65847.
   879  	toolchain := wf.Toolchain.Name
   880  	toolVers := gover.FromToolchain(toolchain)
   881  	if toolchain == "go"+goVers || gover.Compare(toolVers, goVers) < 0 || gover.Compare(toolVers, gover.GoStrictVersion) < 0 {
   882  		wf.DropToolchainStmt()
   883  	}
   884  
   885  	return true
   886  }
   887  
   888  // UpdateWorkFile updates comments on directory directives in the go.work
   889  // file to include the associated module path.
   890  func UpdateWorkFile(wf *modfile.WorkFile) {
   891  	missingModulePaths := map[string]string{} // module directory listed in file -> abspath modroot
   892  
   893  	for _, d := range wf.Use {
   894  		if d.Path == "" {
   895  			continue // d is marked for deletion.
   896  		}
   897  		modRoot := d.Path
   898  		if d.ModulePath == "" {
   899  			missingModulePaths[d.Path] = modRoot
   900  		}
   901  	}
   902  
   903  	// Clean up and annotate directories.
   904  	// TODO(matloob): update x/mod to actually add module paths.
   905  	for moddir, absmodroot := range missingModulePaths {
   906  		_, f, err := ReadModFile(filepath.Join(absmodroot, "go.mod"), nil)
   907  		if err != nil {
   908  			continue // Error will be reported if modules are loaded.
   909  		}
   910  		wf.AddUse(moddir, f.Module.Mod.Path)
   911  	}
   912  }
   913  
   914  // LoadModFile sets Target and, if there is a main module, parses the initial
   915  // build list from its go.mod file.
   916  //
   917  // LoadModFile may make changes in memory, like adding a go directive and
   918  // ensuring requirements are consistent. The caller is responsible for ensuring
   919  // those changes are written to disk by calling LoadPackages or ListModules
   920  // (unless ExplicitWriteGoMod is set) or by calling WriteGoMod directly.
   921  //
   922  // As a side-effect, LoadModFile may change cfg.BuildMod to "vendor" if
   923  // -mod wasn't set explicitly and automatic vendoring should be enabled.
   924  //
   925  // If LoadModFile or CreateModFile has already been called, LoadModFile returns
   926  // the existing in-memory requirements (rather than re-reading them from disk).
   927  //
   928  // LoadModFile checks the roots of the module graph for consistency with each
   929  // other, but unlike LoadModGraph does not load the full module graph or check
   930  // it for global consistency. Most callers outside of the modload package should
   931  // use LoadModGraph instead.
   932  func LoadModFile(loaderstate *State, ctx context.Context) *Requirements {
   933  	rs, err := loadModFile(loaderstate, ctx, nil)
   934  	if err != nil {
   935  		base.Fatal(err)
   936  	}
   937  	return rs
   938  }
   939  
   940  func loadModFile(loaderstate *State, ctx context.Context, opts *PackageOpts) (*Requirements, error) {
   941  	if loaderstate.requirements != nil {
   942  		return loaderstate.requirements, nil
   943  	}
   944  
   945  	Init(loaderstate)
   946  	var workFile *modfile.WorkFile
   947  	if loaderstate.inWorkspaceMode() {
   948  		var err error
   949  		workFile, loaderstate.modRoots, err = LoadWorkFile(loaderstate.workFilePath)
   950  		if err != nil {
   951  			return nil, err
   952  		}
   953  		for _, modRoot := range loaderstate.modRoots {
   954  			sumFile := strings.TrimSuffix(modFilePath(modRoot), ".mod") + ".sum"
   955  			loaderstate.Fetcher().AddWorkspaceGoSumFile(sumFile)
   956  		}
   957  		loaderstate.Fetcher().SetGoSumFile(loaderstate.workFilePath + ".sum")
   958  	} else if len(loaderstate.modRoots) == 0 {
   959  		// We're in module mode, but not inside a module.
   960  		//
   961  		// Commands like 'go build', 'go run', 'go list' have no go.mod file to
   962  		// read or write. They would need to find and download the latest versions
   963  		// of a potentially large number of modules with no way to save version
   964  		// information. We can succeed slowly (but not reproducibly), but that's
   965  		// not usually a good experience.
   966  		//
   967  		// Instead, we forbid resolving import paths to modules other than std and
   968  		// cmd. Users may still build packages specified with .go files on the
   969  		// command line, but they'll see an error if those files import anything
   970  		// outside std.
   971  		//
   972  		// This can be overridden by calling AllowMissingModuleImports.
   973  		// For example, 'go get' does this, since it is expected to resolve paths.
   974  		//
   975  		// See golang.org/issue/32027.
   976  	} else {
   977  		loaderstate.Fetcher().SetGoSumFile(strings.TrimSuffix(modFilePath(loaderstate.modRoots[0]), ".mod") + ".sum")
   978  	}
   979  	if len(loaderstate.modRoots) == 0 {
   980  		// TODO(#49228): Instead of creating a fake module with an empty modroot,
   981  		// make MainModules.Len() == 0 mean that we're in module mode but not inside
   982  		// any module.
   983  		mainModule := module.Version{Path: "command-line-arguments"}
   984  		loaderstate.MainModules = makeMainModules(loaderstate, []module.Version{mainModule}, []string{""}, []*modfile.File{nil}, []*modFileIndex{nil}, nil)
   985  		var (
   986  			goVersion string
   987  			pruning   modPruning
   988  			roots     []module.Version
   989  			direct    = map[string]bool{"go": true}
   990  		)
   991  		if loaderstate.inWorkspaceMode() {
   992  			// Since we are in a workspace, the Go version for the synthetic
   993  			// "command-line-arguments" module must not exceed the Go version
   994  			// for the workspace.
   995  			goVersion = loaderstate.MainModules.GoVersion(loaderstate)
   996  			pruning = workspace
   997  			roots = []module.Version{
   998  				mainModule,
   999  				{Path: "go", Version: goVersion},
  1000  				{Path: "toolchain", Version: gover.LocalToolchain()},
  1001  			}
  1002  		} else {
  1003  			goVersion = gover.Local()
  1004  			pruning = pruningForGoVersion(goVersion)
  1005  			roots = []module.Version{
  1006  				{Path: "go", Version: goVersion},
  1007  				{Path: "toolchain", Version: gover.LocalToolchain()},
  1008  			}
  1009  		}
  1010  		rawGoVersion.Store(mainModule, goVersion)
  1011  		loaderstate.requirements = newRequirements(loaderstate, pruning, roots, direct)
  1012  		if cfg.BuildMod == "vendor" {
  1013  			// For issue 56536: Some users may have GOFLAGS=-mod=vendor set.
  1014  			// Make sure it behaves as though the fake module is vendored
  1015  			// with no dependencies.
  1016  			loaderstate.requirements.initVendor(loaderstate, nil)
  1017  		}
  1018  		return loaderstate.requirements, nil
  1019  	}
  1020  
  1021  	var modFiles []*modfile.File
  1022  	var mainModules []module.Version
  1023  	var indices []*modFileIndex
  1024  	var errs []error
  1025  	for _, modroot := range loaderstate.modRoots {
  1026  		gomod := modFilePath(modroot)
  1027  		var fixed bool
  1028  		data, f, err := ReadModFile(gomod, fixVersion(loaderstate, ctx, &fixed))
  1029  		if err != nil {
  1030  			if loaderstate.inWorkspaceMode() {
  1031  				if tooNew, ok := err.(*gover.TooNewError); ok && !strings.HasPrefix(cfg.CmdName, "work ") {
  1032  					// Switching to a newer toolchain won't help - the go.work has the wrong version.
  1033  					// Report this more specific error, unless we are a command like 'go work use'
  1034  					// or 'go work sync', which will fix the problem after the caller sees the TooNewError
  1035  					// and switches to a newer toolchain.
  1036  					err = errWorkTooOld(gomod, workFile, tooNew.GoVersion)
  1037  				} else {
  1038  					err = fmt.Errorf("cannot load module %s listed in go.work file: %w",
  1039  						base.ShortPath(filepath.Dir(gomod)), base.ShortPathError(err))
  1040  				}
  1041  			}
  1042  			errs = append(errs, err)
  1043  			continue
  1044  		}
  1045  		if loaderstate.inWorkspaceMode() && !strings.HasPrefix(cfg.CmdName, "work ") {
  1046  			// Refuse to use workspace if its go version is too old.
  1047  			// Disable this check if we are a workspace command like work use or work sync,
  1048  			// which will fix the problem.
  1049  			mv := gover.FromGoMod(f)
  1050  			wv := gover.FromGoWork(workFile)
  1051  			if gover.Compare(mv, wv) > 0 && gover.Compare(mv, gover.GoStrictVersion) >= 0 {
  1052  				errs = append(errs, errWorkTooOld(gomod, workFile, mv))
  1053  				continue
  1054  			}
  1055  		}
  1056  
  1057  		if !loaderstate.inWorkspaceMode() {
  1058  			ok := true
  1059  			for _, g := range f.Godebug {
  1060  				if err := CheckGodebug("godebug", g.Key, g.Value); err != nil {
  1061  					errs = append(errs, fmt.Errorf("error loading go.mod:\n%s:%d: %v", base.ShortPath(gomod), g.Syntax.Start.Line, err))
  1062  					ok = false
  1063  				}
  1064  			}
  1065  			if !ok {
  1066  				continue
  1067  			}
  1068  		}
  1069  
  1070  		modFiles = append(modFiles, f)
  1071  		mainModule := f.Module.Mod
  1072  		mainModules = append(mainModules, mainModule)
  1073  		indices = append(indices, indexModFile(data, f, mainModule, fixed))
  1074  
  1075  		if err := module.CheckImportPath(f.Module.Mod.Path); err != nil {
  1076  			if pathErr, ok := err.(*module.InvalidPathError); ok {
  1077  				pathErr.Kind = "module"
  1078  			}
  1079  			errs = append(errs, err)
  1080  		}
  1081  	}
  1082  	if len(errs) > 0 {
  1083  		return nil, errors.Join(errs...)
  1084  	}
  1085  
  1086  	loaderstate.MainModules = makeMainModules(loaderstate, mainModules, loaderstate.modRoots, modFiles, indices, workFile)
  1087  	setDefaultBuildMod(loaderstate) // possibly enable automatic vendoring
  1088  	rs := requirementsFromModFiles(loaderstate, ctx, workFile, modFiles, opts)
  1089  
  1090  	if cfg.BuildMod == "vendor" {
  1091  		readVendorList(VendorDir(loaderstate))
  1092  		versions := loaderstate.MainModules.Versions()
  1093  		indexes := make([]*modFileIndex, 0, len(versions))
  1094  		modFiles := make([]*modfile.File, 0, len(versions))
  1095  		modRoots := make([]string, 0, len(versions))
  1096  		for _, m := range versions {
  1097  			indexes = append(indexes, loaderstate.MainModules.Index(m))
  1098  			modFiles = append(modFiles, loaderstate.MainModules.ModFile(m))
  1099  			modRoots = append(modRoots, loaderstate.MainModules.ModRoot(m))
  1100  		}
  1101  		checkVendorConsistency(loaderstate, indexes, modFiles, modRoots)
  1102  		rs.initVendor(loaderstate, vendorList)
  1103  	}
  1104  
  1105  	if loaderstate.inWorkspaceMode() {
  1106  		// We don't need to update the mod file so return early.
  1107  		loaderstate.requirements = rs
  1108  		return rs, nil
  1109  	}
  1110  
  1111  	mainModule := loaderstate.MainModules.mustGetSingleMainModule(loaderstate)
  1112  
  1113  	if rs.hasRedundantRoot(loaderstate) {
  1114  		// If any module path appears more than once in the roots, we know that the
  1115  		// go.mod file needs to be updated even though we have not yet loaded any
  1116  		// transitive dependencies.
  1117  		var err error
  1118  		rs, err = updateRoots(loaderstate, ctx, rs.direct, rs, nil, nil, false)
  1119  		if err != nil {
  1120  			return nil, err
  1121  		}
  1122  	}
  1123  
  1124  	if loaderstate.MainModules.Index(mainModule).goVersion == "" && rs.pruning != workspace {
  1125  		// TODO(#45551): Do something more principled instead of checking
  1126  		// cfg.CmdName directly here.
  1127  		if cfg.BuildMod == "mod" && cfg.CmdName != "mod graph" && cfg.CmdName != "mod why" {
  1128  			// go line is missing from go.mod; add one there and add to derived requirements.
  1129  			v := gover.Local()
  1130  			if opts != nil && opts.TidyGoVersion != "" {
  1131  				v = opts.TidyGoVersion
  1132  			}
  1133  			addGoStmt(loaderstate.MainModules.ModFile(mainModule), mainModule, v)
  1134  			rs = overrideRoots(loaderstate, ctx, rs, []module.Version{{Path: "go", Version: v}})
  1135  
  1136  			// We need to add a 'go' version to the go.mod file, but we must assume
  1137  			// that its existing contents match something between Go 1.11 and 1.16.
  1138  			// Go 1.11 through 1.16 do not support graph pruning, but the latest Go
  1139  			// version uses a pruned module graph — so we need to convert the
  1140  			// requirements to support pruning.
  1141  			if gover.Compare(v, gover.ExplicitIndirectVersion) >= 0 {
  1142  				var err error
  1143  				rs, err = convertPruning(loaderstate, ctx, rs, pruned)
  1144  				if err != nil {
  1145  					return nil, err
  1146  				}
  1147  			}
  1148  		} else {
  1149  			rawGoVersion.Store(mainModule, gover.DefaultGoModVersion)
  1150  		}
  1151  	}
  1152  
  1153  	loaderstate.requirements = rs
  1154  	return loaderstate.requirements, nil
  1155  }
  1156  
  1157  func errWorkTooOld(gomod string, wf *modfile.WorkFile, goVers string) error {
  1158  	verb := "lists"
  1159  	if wf == nil || wf.Go == nil {
  1160  		// A go.work file implicitly requires go1.18
  1161  		// even when it doesn't list any version.
  1162  		verb = "implicitly requires"
  1163  	}
  1164  	return fmt.Errorf("module %s listed in go.work file requires go >= %s, but go.work %s go %s; to download and use go %s:\n\tgo work use",
  1165  		base.ShortPath(filepath.Dir(gomod)), goVers, verb, gover.FromGoWork(wf), goVers)
  1166  }
  1167  
  1168  // CheckReservedModulePath checks whether the module path is a reserved module path
  1169  // that can't be used for a user's module.
  1170  func CheckReservedModulePath(path string) error {
  1171  	if gover.IsToolchain(path) {
  1172  		return errors.New("module path is reserved")
  1173  	}
  1174  
  1175  	return nil
  1176  }
  1177  
  1178  // CreateModFile initializes a new module by creating a go.mod file.
  1179  //
  1180  // If modPath is empty, CreateModFile will attempt to infer the path from the
  1181  // directory location within GOPATH.
  1182  //
  1183  // If a vendoring configuration file is present, CreateModFile will attempt to
  1184  // translate it to go.mod directives. The resulting build list may not be
  1185  // exactly the same as in the legacy configuration (for example, we can't get
  1186  // packages at multiple versions from the same module).
  1187  func CreateModFile(loaderstate *State, ctx context.Context, modPath string) {
  1188  	modRoot := base.Cwd()
  1189  	loaderstate.modRoots = []string{modRoot}
  1190  	Init(loaderstate)
  1191  	modFilePath := modFilePath(modRoot)
  1192  	if _, err := fsys.Stat(modFilePath); err == nil {
  1193  		base.Fatalf("go: %s already exists", modFilePath)
  1194  	}
  1195  
  1196  	if modPath == "" {
  1197  		var err error
  1198  		modPath, err = findModulePath(modRoot)
  1199  		if err != nil {
  1200  			base.Fatal(err)
  1201  		}
  1202  	}
  1203  	checkModulePath(modPath)
  1204  
  1205  	fmt.Fprintf(os.Stderr, "go: creating new go.mod: module %s\n", modPath)
  1206  	modFile := new(modfile.File)
  1207  	modFile.AddModuleStmt(modPath)
  1208  	loaderstate.MainModules = makeMainModules(loaderstate, []module.Version{modFile.Module.Mod}, []string{modRoot}, []*modfile.File{modFile}, []*modFileIndex{nil}, nil)
  1209  	addGoStmt(modFile, modFile.Module.Mod, gover.Local()) // Add the go directive before converted module requirements.
  1210  
  1211  	rs := requirementsFromModFiles(loaderstate, ctx, nil, []*modfile.File{modFile}, nil)
  1212  	rs, err := updateRoots(loaderstate, ctx, rs.direct, rs, nil, nil, false)
  1213  	if err != nil {
  1214  		base.Fatal(err)
  1215  	}
  1216  	loaderstate.requirements = rs
  1217  	if err := commitRequirements(loaderstate, ctx, WriteOpts{}); err != nil {
  1218  		base.Fatal(err)
  1219  	}
  1220  
  1221  	// Suggest running 'go mod tidy' unless the project is empty. Even if we
  1222  	// imported all the correct requirements above, we're probably missing
  1223  	// some sums, so the next build command in -mod=readonly will likely fail.
  1224  	//
  1225  	// We look for non-hidden .go files or subdirectories to determine whether
  1226  	// this is an existing project. Walking the tree for packages would be more
  1227  	// accurate, but could take much longer.
  1228  	empty := true
  1229  	files, _ := os.ReadDir(modRoot)
  1230  	for _, f := range files {
  1231  		name := f.Name()
  1232  		if strings.HasPrefix(name, ".") || strings.HasPrefix(name, "_") {
  1233  			continue
  1234  		}
  1235  		if strings.HasSuffix(name, ".go") || f.IsDir() {
  1236  			empty = false
  1237  			break
  1238  		}
  1239  	}
  1240  	if !empty {
  1241  		fmt.Fprintf(os.Stderr, "go: to add module requirements and sums:\n\tgo mod tidy\n")
  1242  	}
  1243  }
  1244  
  1245  func checkModulePath(modPath string) {
  1246  	if err := module.CheckImportPath(modPath); err != nil {
  1247  		if pathErr, ok := err.(*module.InvalidPathError); ok {
  1248  			pathErr.Kind = "module"
  1249  			// Same as build.IsLocalPath()
  1250  			if pathErr.Path == "." || pathErr.Path == ".." ||
  1251  				strings.HasPrefix(pathErr.Path, "./") || strings.HasPrefix(pathErr.Path, "../") {
  1252  				pathErr.Err = errors.New("is a local import path")
  1253  			}
  1254  		}
  1255  		base.Fatal(err)
  1256  	}
  1257  	if err := CheckReservedModulePath(modPath); err != nil {
  1258  		base.Fatalf(`go: invalid module path %q: `, modPath)
  1259  	}
  1260  	if _, _, ok := module.SplitPathVersion(modPath); !ok {
  1261  		if strings.HasPrefix(modPath, "gopkg.in/") {
  1262  			invalidMajorVersionMsg := fmt.Errorf("module paths beginning with gopkg.in/ must always have a major version suffix in the form of .vN:\n\tgo mod init %s", suggestGopkgIn(modPath))
  1263  			base.Fatalf(`go: invalid module path "%v": %v`, modPath, invalidMajorVersionMsg)
  1264  		}
  1265  		invalidMajorVersionMsg := fmt.Errorf("major version suffixes must be in the form of /vN and are only allowed for v2 or later:\n\tgo mod init %s", suggestModulePath(modPath))
  1266  		base.Fatalf(`go: invalid module path "%v": %v`, modPath, invalidMajorVersionMsg)
  1267  	}
  1268  }
  1269  
  1270  // fixVersion returns a modfile.VersionFixer implemented using the Query function.
  1271  //
  1272  // It resolves commit hashes and branch names to versions,
  1273  // canonicalizes versions that appeared in early vgo drafts,
  1274  // and does nothing for versions that already appear to be canonical.
  1275  //
  1276  // The VersionFixer sets 'fixed' if it ever returns a non-canonical version.
  1277  func fixVersion(loaderstate *State, ctx context.Context, fixed *bool) modfile.VersionFixer {
  1278  	return func(path, vers string) (resolved string, err error) {
  1279  		defer func() {
  1280  			if err == nil && resolved != vers {
  1281  				*fixed = true
  1282  			}
  1283  		}()
  1284  
  1285  		// Special case: remove the old -gopkgin- hack.
  1286  		if strings.HasPrefix(path, "gopkg.in/") && strings.Contains(vers, "-gopkgin-") {
  1287  			vers = vers[strings.Index(vers, "-gopkgin-")+len("-gopkgin-"):]
  1288  		}
  1289  
  1290  		// fixVersion is called speculatively on every
  1291  		// module, version pair from every go.mod file.
  1292  		// Avoid the query if it looks OK.
  1293  		_, pathMajor, ok := module.SplitPathVersion(path)
  1294  		if !ok {
  1295  			return "", &module.ModuleError{
  1296  				Path: path,
  1297  				Err: &module.InvalidVersionError{
  1298  					Version: vers,
  1299  					Err:     fmt.Errorf("malformed module path %q", path),
  1300  				},
  1301  			}
  1302  		}
  1303  		if vers != "" && module.CanonicalVersion(vers) == vers {
  1304  			if err := module.CheckPathMajor(vers, pathMajor); err != nil {
  1305  				return "", module.VersionError(module.Version{Path: path, Version: vers}, err)
  1306  			}
  1307  			return vers, nil
  1308  		}
  1309  
  1310  		info, err := Query(loaderstate, ctx, path, vers, "", nil)
  1311  		if err != nil {
  1312  			return "", err
  1313  		}
  1314  		return info.Version, nil
  1315  	}
  1316  }
  1317  
  1318  // AllowMissingModuleImports allows import paths to be resolved to modules
  1319  // when there is no module root. Normally, this is forbidden because it's slow
  1320  // and there's no way to make the result reproducible, but some commands
  1321  // like 'go get' are expected to do this.
  1322  //
  1323  // This function affects the default cfg.BuildMod when outside of a module,
  1324  // so it can only be called prior to Init.
  1325  func (s *State) AllowMissingModuleImports() {
  1326  	if s.initialized {
  1327  		panic("AllowMissingModuleImports after Init")
  1328  	}
  1329  	s.allowMissingModuleImports = true
  1330  }
  1331  
  1332  // makeMainModules creates a MainModuleSet and associated variables according to
  1333  // the given main modules.
  1334  func makeMainModules(loaderstate *State, ms []module.Version, rootDirs []string, modFiles []*modfile.File, indices []*modFileIndex, workFile *modfile.WorkFile) *MainModuleSet {
  1335  	for _, m := range ms {
  1336  		if m.Version != "" {
  1337  			panic("mainModulesCalled with module.Version with non empty Version field: " + fmt.Sprintf("%#v", m))
  1338  		}
  1339  	}
  1340  	modRootContainingCWD := findModuleRoot(base.Cwd())
  1341  	mainModules := &MainModuleSet{
  1342  		versions:        slices.Clip(ms),
  1343  		inGorootSrc:     map[module.Version]bool{},
  1344  		pathPrefix:      map[module.Version]string{},
  1345  		modRoot:         map[module.Version]string{},
  1346  		modFiles:        map[module.Version]*modfile.File{},
  1347  		indices:         map[module.Version]*modFileIndex{},
  1348  		highestReplaced: map[string]string{},
  1349  		tools:           map[string]bool{},
  1350  		workFile:        workFile,
  1351  	}
  1352  	var workFileReplaces []*modfile.Replace
  1353  	if workFile != nil {
  1354  		workFileReplaces = workFile.Replace
  1355  		mainModules.workFileReplaceMap = toReplaceMap(workFile.Replace)
  1356  	}
  1357  	mainModulePaths := make(map[string]bool)
  1358  	for _, m := range ms {
  1359  		if mainModulePaths[m.Path] {
  1360  			base.Errorf("go: module %s appears multiple times in workspace", m.Path)
  1361  		}
  1362  		mainModulePaths[m.Path] = true
  1363  	}
  1364  	replacedByWorkFile := make(map[string]bool)
  1365  	replacements := make(map[module.Version]module.Version)
  1366  	for _, r := range workFileReplaces {
  1367  		if mainModulePaths[r.Old.Path] && r.Old.Version == "" {
  1368  			base.Errorf("go: workspace module %v is replaced at all versions in the go.work file. To fix, remove the replacement from the go.work file or specify the version at which to replace the module.", r.Old.Path)
  1369  		}
  1370  		replacedByWorkFile[r.Old.Path] = true
  1371  		v, ok := mainModules.highestReplaced[r.Old.Path]
  1372  		if !ok || gover.ModCompare(r.Old.Path, r.Old.Version, v) > 0 {
  1373  			mainModules.highestReplaced[r.Old.Path] = r.Old.Version
  1374  		}
  1375  		replacements[r.Old] = r.New
  1376  	}
  1377  	for i, m := range ms {
  1378  		mainModules.pathPrefix[m] = m.Path
  1379  		mainModules.modRoot[m] = rootDirs[i]
  1380  		mainModules.modFiles[m] = modFiles[i]
  1381  		mainModules.indices[m] = indices[i]
  1382  
  1383  		if mainModules.modRoot[m] == modRootContainingCWD {
  1384  			mainModules.modContainingCWD = m
  1385  		}
  1386  
  1387  		if rel := search.InDir(rootDirs[i], cfg.GOROOTsrc); rel != "" {
  1388  			mainModules.inGorootSrc[m] = true
  1389  			if m.Path == "std" {
  1390  				// The "std" module in GOROOT/src is the Go standard library. Unlike other
  1391  				// modules, the packages in the "std" module have no import-path prefix.
  1392  				//
  1393  				// Modules named "std" outside of GOROOT/src do not receive this special
  1394  				// treatment, so it is possible to run 'go test .' in other GOROOTs to
  1395  				// test individual packages using a combination of the modified package
  1396  				// and the ordinary standard library.
  1397  				// (See https://golang.org/issue/30756.)
  1398  				mainModules.pathPrefix[m] = ""
  1399  			}
  1400  		}
  1401  
  1402  		if modFiles[i] != nil {
  1403  			curModuleReplaces := make(map[module.Version]bool)
  1404  			for _, r := range modFiles[i].Replace {
  1405  				if replacedByWorkFile[r.Old.Path] {
  1406  					continue
  1407  				}
  1408  				var newV module.Version = r.New
  1409  				if WorkFilePath(loaderstate) != "" && newV.Version == "" && !filepath.IsAbs(newV.Path) {
  1410  					// Since we are in a workspace, we may be loading replacements from
  1411  					// multiple go.mod files. Relative paths in those replacement are
  1412  					// relative to the go.mod file, not the workspace, so the same string
  1413  					// may refer to two different paths and different strings may refer to
  1414  					// the same path. Convert them all to be absolute instead.
  1415  					//
  1416  					// (We could do this outside of a workspace too, but it would mean that
  1417  					// replacement paths in error strings needlessly differ from what's in
  1418  					// the go.mod file.)
  1419  					newV.Path = filepath.Join(rootDirs[i], newV.Path)
  1420  				}
  1421  				if prev, ok := replacements[r.Old]; ok && !curModuleReplaces[r.Old] && prev != newV {
  1422  					base.Fatalf("go: conflicting replacements for %v:\n\t%v\n\t%v\nuse \"go work edit -replace %v=[override]\" to resolve", r.Old, prev, newV, r.Old)
  1423  				}
  1424  				curModuleReplaces[r.Old] = true
  1425  				replacements[r.Old] = newV
  1426  
  1427  				v, ok := mainModules.highestReplaced[r.Old.Path]
  1428  				if !ok || gover.ModCompare(r.Old.Path, r.Old.Version, v) > 0 {
  1429  					mainModules.highestReplaced[r.Old.Path] = r.Old.Version
  1430  				}
  1431  			}
  1432  
  1433  			for _, t := range modFiles[i].Tool {
  1434  				if err := module.CheckImportPath(t.Path); err != nil {
  1435  					if e, ok := err.(*module.InvalidPathError); ok {
  1436  						e.Kind = "tool"
  1437  					}
  1438  					base.Fatal(err)
  1439  				}
  1440  
  1441  				mainModules.tools[t.Path] = true
  1442  			}
  1443  		}
  1444  	}
  1445  
  1446  	return mainModules
  1447  }
  1448  
  1449  // requirementsFromModFiles returns the set of non-excluded requirements from
  1450  // the global modFile.
  1451  func requirementsFromModFiles(loaderstate *State, ctx context.Context, workFile *modfile.WorkFile, modFiles []*modfile.File, opts *PackageOpts) *Requirements {
  1452  	var roots []module.Version
  1453  	direct := map[string]bool{}
  1454  	var pruning modPruning
  1455  	if loaderstate.inWorkspaceMode() {
  1456  		pruning = workspace
  1457  		roots = make([]module.Version, len(loaderstate.MainModules.Versions()), 2+len(loaderstate.MainModules.Versions()))
  1458  		copy(roots, loaderstate.MainModules.Versions())
  1459  		goVersion := gover.FromGoWork(workFile)
  1460  		var toolchain string
  1461  		if workFile.Toolchain != nil {
  1462  			toolchain = workFile.Toolchain.Name
  1463  		}
  1464  		roots = appendGoAndToolchainRoots(roots, goVersion, toolchain, direct)
  1465  		direct = directRequirements(modFiles)
  1466  	} else {
  1467  		pruning = pruningForGoVersion(loaderstate.MainModules.GoVersion(loaderstate))
  1468  		if len(modFiles) != 1 {
  1469  			panic(fmt.Errorf("requirementsFromModFiles called with %v modfiles outside workspace mode", len(modFiles)))
  1470  		}
  1471  		modFile := modFiles[0]
  1472  		roots, direct = rootsFromModFile(loaderstate, loaderstate.MainModules.mustGetSingleMainModule(loaderstate), modFile, withToolchainRoot)
  1473  	}
  1474  
  1475  	gover.ModSort(roots)
  1476  	rs := newRequirements(loaderstate, pruning, roots, direct)
  1477  	return rs
  1478  }
  1479  
  1480  type addToolchainRoot bool
  1481  
  1482  const (
  1483  	omitToolchainRoot addToolchainRoot = false
  1484  	withToolchainRoot                  = true
  1485  )
  1486  
  1487  func directRequirements(modFiles []*modfile.File) map[string]bool {
  1488  	direct := make(map[string]bool)
  1489  	for _, modFile := range modFiles {
  1490  		for _, r := range modFile.Require {
  1491  			if !r.Indirect {
  1492  				direct[r.Mod.Path] = true
  1493  			}
  1494  		}
  1495  	}
  1496  	return direct
  1497  }
  1498  
  1499  func rootsFromModFile(loaderstate *State, m module.Version, modFile *modfile.File, addToolchainRoot addToolchainRoot) (roots []module.Version, direct map[string]bool) {
  1500  	direct = make(map[string]bool)
  1501  	padding := 2 // Add padding for the toolchain and go version, added upon return.
  1502  	if !addToolchainRoot {
  1503  		padding = 1
  1504  	}
  1505  	roots = make([]module.Version, 0, padding+len(modFile.Require))
  1506  	for _, r := range modFile.Require {
  1507  		if index := loaderstate.MainModules.Index(m); index != nil && index.exclude[r.Mod] {
  1508  			if cfg.BuildMod == "mod" {
  1509  				fmt.Fprintf(os.Stderr, "go: dropping requirement on excluded version %s %s\n", r.Mod.Path, r.Mod.Version)
  1510  			} else {
  1511  				fmt.Fprintf(os.Stderr, "go: ignoring requirement on excluded version %s %s\n", r.Mod.Path, r.Mod.Version)
  1512  			}
  1513  			continue
  1514  		}
  1515  
  1516  		roots = append(roots, r.Mod)
  1517  		if !r.Indirect {
  1518  			direct[r.Mod.Path] = true
  1519  		}
  1520  	}
  1521  	goVersion := gover.FromGoMod(modFile)
  1522  	var toolchain string
  1523  	if addToolchainRoot && modFile.Toolchain != nil {
  1524  		toolchain = modFile.Toolchain.Name
  1525  	}
  1526  	roots = appendGoAndToolchainRoots(roots, goVersion, toolchain, direct)
  1527  	return roots, direct
  1528  }
  1529  
  1530  func appendGoAndToolchainRoots(roots []module.Version, goVersion, toolchain string, direct map[string]bool) []module.Version {
  1531  	// Add explicit go and toolchain versions, inferring as needed.
  1532  	roots = append(roots, module.Version{Path: "go", Version: goVersion})
  1533  	direct["go"] = true // Every module directly uses the language and runtime.
  1534  
  1535  	if toolchain != "" {
  1536  		roots = append(roots, module.Version{Path: "toolchain", Version: toolchain})
  1537  		// Leave the toolchain as indirect: nothing in the user's module directly
  1538  		// imports a package from the toolchain, and (like an indirect dependency in
  1539  		// a module without graph pruning) we may remove the toolchain line
  1540  		// automatically if the 'go' version is changed so that it implies the exact
  1541  		// same toolchain.
  1542  	}
  1543  	return roots
  1544  }
  1545  
  1546  // setDefaultBuildMod sets a default value for cfg.BuildMod if the -mod flag
  1547  // wasn't provided. setDefaultBuildMod may be called multiple times.
  1548  func setDefaultBuildMod(loaderstate *State) {
  1549  	if cfg.BuildModExplicit {
  1550  		if loaderstate.inWorkspaceMode() && cfg.BuildMod != "readonly" && cfg.BuildMod != "vendor" {
  1551  			switch cfg.CmdName {
  1552  			case "work sync", "mod graph", "mod verify", "mod why":
  1553  				// These commands run with BuildMod set to mod, but they don't take the
  1554  				// -mod flag, so we should never get here.
  1555  				panic("in workspace mode and -mod was set explicitly, but command doesn't support setting -mod")
  1556  			default:
  1557  				base.Fatalf("go: -mod may only be set to readonly or vendor when in workspace mode, but it is set to %q"+
  1558  					"\n\tRemove the -mod flag to use the default readonly value, "+
  1559  					"\n\tor set GOWORK=off to disable workspace mode.", cfg.BuildMod)
  1560  			}
  1561  		}
  1562  		// Don't override an explicit '-mod=' argument.
  1563  		return
  1564  	}
  1565  
  1566  	// TODO(#40775): commands should pass in the module mode as an option
  1567  	// to modload functions instead of relying on an implicit setting
  1568  	// based on command name.
  1569  	switch cfg.CmdName {
  1570  	case "get", "mod download", "mod init", "mod tidy", "work sync":
  1571  		// These commands are intended to update go.mod and go.sum.
  1572  		cfg.BuildMod = "mod"
  1573  		return
  1574  	case "mod graph", "mod verify", "mod why":
  1575  		// These commands should not update go.mod or go.sum, but they should be
  1576  		// able to fetch modules not in go.sum and should not report errors if
  1577  		// go.mod is inconsistent. They're useful for debugging, and they need
  1578  		// to work in buggy situations.
  1579  		cfg.BuildMod = "mod"
  1580  		return
  1581  	case "mod vendor", "work vendor":
  1582  		cfg.BuildMod = "readonly"
  1583  		return
  1584  	}
  1585  	if loaderstate.modRoots == nil {
  1586  		if loaderstate.allowMissingModuleImports {
  1587  			cfg.BuildMod = "mod"
  1588  		} else {
  1589  			cfg.BuildMod = "readonly"
  1590  		}
  1591  		return
  1592  	}
  1593  
  1594  	if len(loaderstate.modRoots) >= 1 {
  1595  		var goVersion string
  1596  		var versionSource string
  1597  		if loaderstate.inWorkspaceMode() {
  1598  			versionSource = "go.work"
  1599  			if wfg := loaderstate.MainModules.WorkFile().Go; wfg != nil {
  1600  				goVersion = wfg.Version
  1601  			}
  1602  		} else {
  1603  			versionSource = "go.mod"
  1604  			index := loaderstate.MainModules.GetSingleIndexOrNil(loaderstate)
  1605  			if index != nil {
  1606  				goVersion = index.goVersion
  1607  			}
  1608  		}
  1609  		vendorDir := ""
  1610  		if loaderstate.workFilePath != "" {
  1611  			vendorDir = filepath.Join(filepath.Dir(loaderstate.workFilePath), "vendor")
  1612  		} else {
  1613  			if len(loaderstate.modRoots) != 1 {
  1614  				panic(fmt.Errorf("outside workspace mode, but have %v modRoots", loaderstate.modRoots))
  1615  			}
  1616  			vendorDir = filepath.Join(loaderstate.modRoots[0], "vendor")
  1617  		}
  1618  		if fi, err := fsys.Stat(vendorDir); err == nil && fi.IsDir() {
  1619  			if goVersion != "" {
  1620  				if gover.Compare(goVersion, "1.14") < 0 {
  1621  					// The go version is less than 1.14. Don't set -mod=vendor by default.
  1622  					// Since a vendor directory exists, we should record why we didn't use it.
  1623  					// This message won't normally be shown, but it may appear with import errors.
  1624  					cfg.BuildModReason = fmt.Sprintf("Go version in "+versionSource+" is %s, so vendor directory was not used.", goVersion)
  1625  				} else {
  1626  					vendoredWorkspace, err := modulesTextIsForWorkspace(vendorDir)
  1627  					if err != nil {
  1628  						base.Fatalf("go: reading modules.txt for vendor directory: %v", err)
  1629  					}
  1630  					if vendoredWorkspace != (versionSource == "go.work") {
  1631  						if vendoredWorkspace {
  1632  							cfg.BuildModReason = "Outside workspace mode, but vendor directory is for a workspace."
  1633  						} else {
  1634  							cfg.BuildModReason = "In workspace mode, but vendor directory is not for a workspace"
  1635  						}
  1636  					} else {
  1637  						// The Go version is at least 1.14, a vendor directory exists, and
  1638  						// the modules.txt was generated in the same mode the command is running in.
  1639  						// Set -mod=vendor by default.
  1640  						cfg.BuildMod = "vendor"
  1641  						cfg.BuildModReason = "Go version in " + versionSource + " is at least 1.14 and vendor directory exists."
  1642  						return
  1643  					}
  1644  				}
  1645  			} else {
  1646  				cfg.BuildModReason = fmt.Sprintf("Go version in %s is unspecified, so vendor directory was not used.", versionSource)
  1647  			}
  1648  		}
  1649  	}
  1650  
  1651  	cfg.BuildMod = "readonly"
  1652  }
  1653  
  1654  func modulesTextIsForWorkspace(vendorDir string) (bool, error) {
  1655  	f, err := fsys.Open(filepath.Join(vendorDir, "modules.txt"))
  1656  	if errors.Is(err, os.ErrNotExist) {
  1657  		// Some vendor directories exist that don't contain modules.txt.
  1658  		// This mostly happens when converting to modules.
  1659  		// We want to preserve the behavior that mod=vendor is set (even though
  1660  		// readVendorList does nothing in that case).
  1661  		return false, nil
  1662  	}
  1663  	if err != nil {
  1664  		return false, err
  1665  	}
  1666  	defer f.Close()
  1667  	var buf [512]byte
  1668  	n, err := f.Read(buf[:])
  1669  	if err != nil && err != io.EOF {
  1670  		return false, err
  1671  	}
  1672  	line, _, _ := strings.Cut(string(buf[:n]), "\n")
  1673  	if annotations, ok := strings.CutPrefix(line, "## "); ok {
  1674  		for entry := range strings.SplitSeq(annotations, ";") {
  1675  			entry = strings.TrimSpace(entry)
  1676  			if entry == "workspace" {
  1677  				return true, nil
  1678  			}
  1679  		}
  1680  	}
  1681  	return false, nil
  1682  }
  1683  
  1684  func mustHaveCompleteRequirements(loaderstate *State) bool {
  1685  	return cfg.BuildMod != "mod" && !loaderstate.inWorkspaceMode()
  1686  }
  1687  
  1688  // addGoStmt adds a go directive to the go.mod file if it does not already
  1689  // include one. The 'go' version added, if any, is the latest version supported
  1690  // by this toolchain.
  1691  func addGoStmt(modFile *modfile.File, mod module.Version, v string) {
  1692  	if modFile.Go != nil && modFile.Go.Version != "" {
  1693  		return
  1694  	}
  1695  	forceGoStmt(modFile, mod, v)
  1696  }
  1697  
  1698  func forceGoStmt(modFile *modfile.File, mod module.Version, v string) {
  1699  	if err := modFile.AddGoStmt(v); err != nil {
  1700  		base.Fatalf("go: internal error: %v", err)
  1701  	}
  1702  	rawGoVersion.Store(mod, v)
  1703  }
  1704  
  1705  var altConfigs = []string{
  1706  	".git/config",
  1707  }
  1708  
  1709  func findModuleRoot(dir string) (roots string) {
  1710  	if dir == "" {
  1711  		panic("dir not set")
  1712  	}
  1713  	dir = filepath.Clean(dir)
  1714  
  1715  	// Look for enclosing go.mod.
  1716  	for {
  1717  		if fi, err := fsys.Stat(filepath.Join(dir, "go.mod")); err == nil && !fi.IsDir() {
  1718  			return dir
  1719  		}
  1720  		d := filepath.Dir(dir)
  1721  		if d == dir {
  1722  			break
  1723  		}
  1724  		dir = d
  1725  	}
  1726  	return ""
  1727  }
  1728  
  1729  func findWorkspaceFile(dir string) (root string) {
  1730  	if dir == "" {
  1731  		panic("dir not set")
  1732  	}
  1733  	dir = filepath.Clean(dir)
  1734  
  1735  	// Look for enclosing go.mod.
  1736  	for {
  1737  		f := filepath.Join(dir, "go.work")
  1738  		if fi, err := fsys.Stat(f); err == nil && !fi.IsDir() {
  1739  			return f
  1740  		}
  1741  		d := filepath.Dir(dir)
  1742  		if d == dir {
  1743  			break
  1744  		}
  1745  		if d == cfg.GOROOT {
  1746  			// As a special case, don't cross GOROOT to find a go.work file.
  1747  			// The standard library and commands built in go always use the vendored
  1748  			// dependencies, so avoid using a most likely irrelevant go.work file.
  1749  			return ""
  1750  		}
  1751  		dir = d
  1752  	}
  1753  	return ""
  1754  }
  1755  
  1756  func findAltConfig(dir string) (root, name string) {
  1757  	if dir == "" {
  1758  		panic("dir not set")
  1759  	}
  1760  	dir = filepath.Clean(dir)
  1761  	if rel := search.InDir(dir, cfg.BuildContext.GOROOT); rel != "" {
  1762  		// Don't suggest creating a module from $GOROOT/.git/config
  1763  		// or a config file found in any parent of $GOROOT (see #34191).
  1764  		return "", ""
  1765  	}
  1766  	for {
  1767  		for _, name := range altConfigs {
  1768  			if fi, err := fsys.Stat(filepath.Join(dir, name)); err == nil && !fi.IsDir() {
  1769  				return dir, name
  1770  			}
  1771  		}
  1772  		d := filepath.Dir(dir)
  1773  		if d == dir {
  1774  			break
  1775  		}
  1776  		dir = d
  1777  	}
  1778  	return "", ""
  1779  }
  1780  
  1781  func findModulePath(dir string) (string, error) {
  1782  	// TODO(bcmills): once we have located a plausible module path, we should
  1783  	// query version control (if available) to verify that it matches the major
  1784  	// version of the most recent tag.
  1785  	// See https://golang.org/issue/29433, https://golang.org/issue/27009, and
  1786  	// https://golang.org/issue/31549.
  1787  
  1788  	// Cast about for import comments,
  1789  	// first in top-level directory, then in subdirectories.
  1790  	list, _ := os.ReadDir(dir)
  1791  	for _, info := range list {
  1792  		if info.Type().IsRegular() && strings.HasSuffix(info.Name(), ".go") {
  1793  			if com := findImportComment(filepath.Join(dir, info.Name())); com != "" {
  1794  				return com, nil
  1795  			}
  1796  		}
  1797  	}
  1798  	for _, info1 := range list {
  1799  		if info1.IsDir() {
  1800  			files, _ := os.ReadDir(filepath.Join(dir, info1.Name()))
  1801  			for _, info2 := range files {
  1802  				if info2.Type().IsRegular() && strings.HasSuffix(info2.Name(), ".go") {
  1803  					if com := findImportComment(filepath.Join(dir, info1.Name(), info2.Name())); com != "" {
  1804  						return path.Dir(com), nil
  1805  					}
  1806  				}
  1807  			}
  1808  		}
  1809  	}
  1810  
  1811  	// Look for path in GOPATH.
  1812  	var badPathErr error
  1813  	for _, gpdir := range filepath.SplitList(cfg.BuildContext.GOPATH) {
  1814  		if gpdir == "" {
  1815  			continue
  1816  		}
  1817  		if rel := search.InDir(dir, filepath.Join(gpdir, "src")); rel != "" && rel != "." {
  1818  			path := filepath.ToSlash(rel)
  1819  			// gorelease will alert users publishing their modules to fix their paths.
  1820  			if err := module.CheckImportPath(path); err != nil {
  1821  				badPathErr = err
  1822  				break
  1823  			}
  1824  			return path, nil
  1825  		}
  1826  	}
  1827  
  1828  	reason := "outside GOPATH, module path must be specified"
  1829  	if badPathErr != nil {
  1830  		// return a different error message if the module was in GOPATH, but
  1831  		// the module path determined above would be an invalid path.
  1832  		reason = fmt.Sprintf("bad module path inferred from directory in GOPATH: %v", badPathErr)
  1833  	}
  1834  	msg := `cannot determine module path for source directory %s (%s)
  1835  
  1836  Example usage:
  1837  	'go mod init example.com/m' to initialize a v0 or v1 module
  1838  	'go mod init example.com/m/v2' to initialize a v2 module
  1839  
  1840  Run 'go help mod init' for more information.
  1841  `
  1842  	return "", fmt.Errorf(msg, dir, reason)
  1843  }
  1844  
  1845  var (
  1846  	importCommentRE = lazyregexp.New(`(?m)^package[ \t]+[^ \t\r\n/]+[ \t]+//[ \t]+import[ \t]+(\"[^"]+\")[ \t]*\r?\n`)
  1847  )
  1848  
  1849  func findImportComment(file string) string {
  1850  	data, err := os.ReadFile(file)
  1851  	if err != nil {
  1852  		return ""
  1853  	}
  1854  	m := importCommentRE.FindSubmatch(data)
  1855  	if m == nil {
  1856  		return ""
  1857  	}
  1858  	path, err := strconv.Unquote(string(m[1]))
  1859  	if err != nil {
  1860  		return ""
  1861  	}
  1862  	return path
  1863  }
  1864  
  1865  // WriteOpts control the behavior of WriteGoMod.
  1866  type WriteOpts struct {
  1867  	DropToolchain     bool // go get toolchain@none
  1868  	ExplicitToolchain bool // go get has set explicit toolchain version
  1869  
  1870  	AddTools  []string // go get -tool example.com/m1
  1871  	DropTools []string // go get -tool example.com/m1@none
  1872  
  1873  	// TODO(bcmills): Make 'go mod tidy' update the go version in the Requirements
  1874  	// instead of writing directly to the modfile.File
  1875  	TidyWroteGo bool // Go.Version field already updated by 'go mod tidy'
  1876  }
  1877  
  1878  // WriteGoMod writes the current build list back to go.mod.
  1879  func WriteGoMod(loaderstate *State, ctx context.Context, opts WriteOpts) error {
  1880  	loaderstate.requirements = LoadModFile(loaderstate, ctx)
  1881  	return commitRequirements(loaderstate, ctx, opts)
  1882  }
  1883  
  1884  var errNoChange = errors.New("no update needed")
  1885  
  1886  // UpdateGoModFromReqs returns a modified go.mod file using the current
  1887  // requirements. It does not commit these changes to disk.
  1888  func UpdateGoModFromReqs(loaderstate *State, ctx context.Context, opts WriteOpts) (before, after []byte, modFile *modfile.File, err error) {
  1889  	if loaderstate.MainModules.Len() != 1 || loaderstate.MainModules.ModRoot(loaderstate.MainModules.Versions()[0]) == "" {
  1890  		// We aren't in a module, so we don't have anywhere to write a go.mod file.
  1891  		return nil, nil, nil, errNoChange
  1892  	}
  1893  	mainModule := loaderstate.MainModules.mustGetSingleMainModule(loaderstate)
  1894  	modFile = loaderstate.MainModules.ModFile(mainModule)
  1895  	if modFile == nil {
  1896  		// command-line-arguments has no .mod file to write.
  1897  		return nil, nil, nil, errNoChange
  1898  	}
  1899  	before, err = modFile.Format()
  1900  	if err != nil {
  1901  		return nil, nil, nil, err
  1902  	}
  1903  
  1904  	var list []*modfile.Require
  1905  	toolchain := ""
  1906  	goVersion := ""
  1907  	for _, m := range loaderstate.requirements.rootModules {
  1908  		if m.Path == "go" {
  1909  			goVersion = m.Version
  1910  			continue
  1911  		}
  1912  		if m.Path == "toolchain" {
  1913  			toolchain = m.Version
  1914  			continue
  1915  		}
  1916  		list = append(list, &modfile.Require{
  1917  			Mod:      m,
  1918  			Indirect: !loaderstate.requirements.direct[m.Path],
  1919  		})
  1920  	}
  1921  
  1922  	// Update go line.
  1923  	// Every MVS graph we consider should have go as a root,
  1924  	// and toolchain is either implied by the go line or explicitly a root.
  1925  	if goVersion == "" {
  1926  		base.Fatalf("go: internal error: missing go root module in WriteGoMod")
  1927  	}
  1928  	if gover.Compare(goVersion, gover.Local()) > 0 {
  1929  		// We cannot assume that we know how to update a go.mod to a newer version.
  1930  		return nil, nil, nil, &gover.TooNewError{What: "updating go.mod", GoVersion: goVersion}
  1931  	}
  1932  	wroteGo := opts.TidyWroteGo
  1933  	if !wroteGo && modFile.Go == nil || modFile.Go.Version != goVersion {
  1934  		alwaysUpdate := cfg.BuildMod == "mod" || cfg.CmdName == "mod tidy" || cfg.CmdName == "get"
  1935  		if modFile.Go == nil && goVersion == gover.DefaultGoModVersion && !alwaysUpdate {
  1936  			// The go.mod has no go line, the implied default Go version matches
  1937  			// what we've computed for the graph, and we're not in one of the
  1938  			// traditional go.mod-updating programs, so leave it alone.
  1939  		} else {
  1940  			wroteGo = true
  1941  			forceGoStmt(modFile, mainModule, goVersion)
  1942  		}
  1943  	}
  1944  	if toolchain == "" {
  1945  		toolchain = "go" + goVersion
  1946  	}
  1947  
  1948  	toolVers := gover.FromToolchain(toolchain)
  1949  	if opts.DropToolchain || toolchain == "go"+goVersion || (gover.Compare(toolVers, gover.GoStrictVersion) < 0 && !opts.ExplicitToolchain) {
  1950  		// go get toolchain@none or toolchain matches go line or isn't valid; drop it.
  1951  		// TODO(#57001): 'go get' should reject explicit toolchains below GoStrictVersion.
  1952  		modFile.DropToolchainStmt()
  1953  	} else {
  1954  		modFile.AddToolchainStmt(toolchain)
  1955  	}
  1956  
  1957  	for _, path := range opts.AddTools {
  1958  		modFile.AddTool(path)
  1959  	}
  1960  
  1961  	for _, path := range opts.DropTools {
  1962  		modFile.DropTool(path)
  1963  	}
  1964  
  1965  	// Update require blocks.
  1966  	if gover.Compare(goVersion, gover.SeparateIndirectVersion) < 0 {
  1967  		modFile.SetRequire(list)
  1968  	} else {
  1969  		modFile.SetRequireSeparateIndirect(list)
  1970  	}
  1971  	modFile.Cleanup()
  1972  	after, err = modFile.Format()
  1973  	if err != nil {
  1974  		return nil, nil, nil, err
  1975  	}
  1976  	return before, after, modFile, nil
  1977  }
  1978  
  1979  // commitRequirements ensures go.mod and go.sum are up to date with the current
  1980  // requirements.
  1981  //
  1982  // In "mod" mode, commitRequirements writes changes to go.mod and go.sum.
  1983  //
  1984  // In "readonly" and "vendor" modes, commitRequirements returns an error if
  1985  // go.mod or go.sum are out of date in a semantically significant way.
  1986  //
  1987  // In workspace mode, commitRequirements only writes changes to go.work.sum.
  1988  func commitRequirements(loaderstate *State, ctx context.Context, opts WriteOpts) (err error) {
  1989  	if loaderstate.inWorkspaceMode() {
  1990  		// go.mod files aren't updated in workspace mode, but we still want to
  1991  		// update the go.work.sum file.
  1992  		return loaderstate.Fetcher().WriteGoSum(ctx, keepSums(loaderstate, ctx, loaderstate.pkgLoader, loaderstate.requirements, addBuildListZipSums), mustHaveCompleteRequirements(loaderstate))
  1993  	}
  1994  	_, updatedGoMod, modFile, err := UpdateGoModFromReqs(loaderstate, ctx, opts)
  1995  	if err != nil {
  1996  		if errors.Is(err, errNoChange) {
  1997  			return nil
  1998  		}
  1999  		return err
  2000  	}
  2001  
  2002  	index := loaderstate.MainModules.GetSingleIndexOrNil(loaderstate)
  2003  	dirty := index.modFileIsDirty(modFile) || len(opts.DropTools) > 0 || len(opts.AddTools) > 0
  2004  	if dirty && cfg.BuildMod != "mod" {
  2005  		// If we're about to fail due to -mod=readonly,
  2006  		// prefer to report a dirty go.mod over a dirty go.sum
  2007  		return errGoModDirty
  2008  	}
  2009  
  2010  	if !dirty && cfg.CmdName != "mod tidy" {
  2011  		// The go.mod file has the same semantic content that it had before
  2012  		// (but not necessarily the same exact bytes).
  2013  		// Don't write go.mod, but write go.sum in case we added or trimmed sums.
  2014  		// 'go mod init' shouldn't write go.sum, since it will be incomplete.
  2015  		if cfg.CmdName != "mod init" {
  2016  			if err := loaderstate.Fetcher().WriteGoSum(ctx, keepSums(loaderstate, ctx, loaderstate.pkgLoader, loaderstate.requirements, addBuildListZipSums), mustHaveCompleteRequirements(loaderstate)); err != nil {
  2017  				return err
  2018  			}
  2019  		}
  2020  		return nil
  2021  	}
  2022  
  2023  	mainModule := loaderstate.MainModules.mustGetSingleMainModule(loaderstate)
  2024  	modFilePath := modFilePath(loaderstate.MainModules.ModRoot(mainModule))
  2025  	if fsys.Replaced(modFilePath) {
  2026  		if dirty {
  2027  			return errors.New("updates to go.mod needed, but go.mod is part of the overlay specified with -overlay")
  2028  		}
  2029  		return nil
  2030  	}
  2031  	defer func() {
  2032  		// At this point we have determined to make the go.mod file on disk equal to new.
  2033  		loaderstate.MainModules.SetIndex(mainModule, indexModFile(updatedGoMod, modFile, mainModule, false))
  2034  
  2035  		// Update go.sum after releasing the side lock and refreshing the index.
  2036  		// 'go mod init' shouldn't write go.sum, since it will be incomplete.
  2037  		if cfg.CmdName != "mod init" {
  2038  			if err == nil {
  2039  				err = loaderstate.Fetcher().WriteGoSum(ctx, keepSums(loaderstate, ctx, loaderstate.pkgLoader, loaderstate.requirements, addBuildListZipSums), mustHaveCompleteRequirements(loaderstate))
  2040  			}
  2041  		}
  2042  	}()
  2043  
  2044  	// Make a best-effort attempt to acquire the side lock, only to exclude
  2045  	// previous versions of the 'go' command from making simultaneous edits.
  2046  	if unlock, err := modfetch.SideLock(ctx); err == nil {
  2047  		defer unlock()
  2048  	}
  2049  
  2050  	err = lockedfile.Transform(modFilePath, func(old []byte) ([]byte, error) {
  2051  		if bytes.Equal(old, updatedGoMod) {
  2052  			// The go.mod file is already equal to new, possibly as the result of some
  2053  			// other process.
  2054  			return nil, errNoChange
  2055  		}
  2056  
  2057  		if index != nil && !bytes.Equal(old, index.data) {
  2058  			// The contents of the go.mod file have changed. In theory we could add all
  2059  			// of the new modules to the build list, recompute, and check whether any
  2060  			// module in *our* build list got bumped to a different version, but that's
  2061  			// a lot of work for marginal benefit. Instead, fail the command: if users
  2062  			// want to run concurrent commands, they need to start with a complete,
  2063  			// consistent module definition.
  2064  			return nil, fmt.Errorf("existing contents have changed since last read")
  2065  		}
  2066  
  2067  		return updatedGoMod, nil
  2068  	})
  2069  
  2070  	if err != nil && err != errNoChange {
  2071  		return fmt.Errorf("updating go.mod: %w", err)
  2072  	}
  2073  	return nil
  2074  }
  2075  
  2076  // keepSums returns the set of modules (and go.mod file entries) for which
  2077  // checksums would be needed in order to reload the same set of packages
  2078  // loaded by the most recent call to LoadPackages or ImportFromFiles,
  2079  // including any go.mod files needed to reconstruct the MVS result
  2080  // or identify go versions,
  2081  // in addition to the checksums for every module in keepMods.
  2082  func keepSums(loaderstate *State, ctx context.Context, ld *packageLoader, rs *Requirements, which whichSums) map[module.Version]bool {
  2083  	// Every module in the full module graph contributes its requirements,
  2084  	// so in order to ensure that the build list itself is reproducible,
  2085  	// we need sums for every go.mod in the graph (regardless of whether
  2086  	// that version is selected).
  2087  	keep := make(map[module.Version]bool)
  2088  
  2089  	// Add entries for modules in the build list with paths that are prefixes of
  2090  	// paths of loaded packages. We need to retain sums for all of these modules —
  2091  	// not just the modules containing the actual packages — in order to rule out
  2092  	// ambiguous import errors the next time we load the package.
  2093  	keepModSumsForZipSums := true
  2094  	if ld == nil {
  2095  		if gover.Compare(loaderstate.MainModules.GoVersion(loaderstate), gover.TidyGoModSumVersion) < 0 && cfg.BuildMod != "mod" {
  2096  			keepModSumsForZipSums = false
  2097  		}
  2098  	} else {
  2099  		keepPkgGoModSums := true
  2100  		if gover.Compare(ld.requirements.GoVersion(loaderstate), gover.TidyGoModSumVersion) < 0 && (ld.Tidy || cfg.BuildMod != "mod") {
  2101  			keepPkgGoModSums = false
  2102  			keepModSumsForZipSums = false
  2103  		}
  2104  		for _, pkg := range ld.pkgs {
  2105  			// We check pkg.mod.Path here instead of pkg.inStd because the
  2106  			// pseudo-package "C" is not in std, but not provided by any module (and
  2107  			// shouldn't force loading the whole module graph).
  2108  			if pkg.testOf != nil || (pkg.mod.Path == "" && pkg.err == nil) || module.CheckImportPath(pkg.path) != nil {
  2109  				continue
  2110  			}
  2111  
  2112  			// We need the checksum for the go.mod file for pkg.mod
  2113  			// so that we know what Go version to use to compile pkg.
  2114  			// However, we didn't do so before Go 1.21, and the bug is relatively
  2115  			// minor, so we maintain the previous (buggy) behavior in 'go mod tidy' to
  2116  			// avoid introducing unnecessary churn.
  2117  			if keepPkgGoModSums {
  2118  				r := resolveReplacement(loaderstate, pkg.mod)
  2119  				keep[modkey(r)] = true
  2120  			}
  2121  
  2122  			if rs.pruning == pruned && pkg.mod.Path != "" {
  2123  				if v, ok := rs.rootSelected(loaderstate, pkg.mod.Path); ok && v == pkg.mod.Version {
  2124  					// pkg was loaded from a root module, and because the main module has
  2125  					// a pruned module graph we do not check non-root modules for
  2126  					// conflicts for packages that can be found in roots. So we only need
  2127  					// the checksums for the root modules that may contain pkg, not all
  2128  					// possible modules.
  2129  					for prefix := pkg.path; prefix != "."; prefix = path.Dir(prefix) {
  2130  						if v, ok := rs.rootSelected(loaderstate, prefix); ok && v != "none" {
  2131  							m := module.Version{Path: prefix, Version: v}
  2132  							r := resolveReplacement(loaderstate, m)
  2133  							keep[r] = true
  2134  						}
  2135  					}
  2136  					continue
  2137  				}
  2138  			}
  2139  
  2140  			mg, _ := rs.Graph(loaderstate, ctx)
  2141  			for prefix := pkg.path; prefix != "."; prefix = path.Dir(prefix) {
  2142  				if v := mg.Selected(prefix); v != "none" {
  2143  					m := module.Version{Path: prefix, Version: v}
  2144  					r := resolveReplacement(loaderstate, m)
  2145  					keep[r] = true
  2146  				}
  2147  			}
  2148  		}
  2149  	}
  2150  
  2151  	if rs.graph.Load() == nil {
  2152  		// We haven't needed to load the module graph so far.
  2153  		// Save sums for the root modules (or their replacements), but don't
  2154  		// incur the cost of loading the graph just to find and retain the sums.
  2155  		for _, m := range rs.rootModules {
  2156  			r := resolveReplacement(loaderstate, m)
  2157  			keep[modkey(r)] = true
  2158  			if which == addBuildListZipSums {
  2159  				keep[r] = true
  2160  			}
  2161  		}
  2162  	} else {
  2163  		mg, _ := rs.Graph(loaderstate, ctx)
  2164  		mg.WalkBreadthFirst(func(m module.Version) {
  2165  			if _, ok := mg.RequiredBy(m); ok {
  2166  				// The requirements from m's go.mod file are present in the module graph,
  2167  				// so they are relevant to the MVS result regardless of whether m was
  2168  				// actually selected.
  2169  				r := resolveReplacement(loaderstate, m)
  2170  				keep[modkey(r)] = true
  2171  			}
  2172  		})
  2173  
  2174  		if which == addBuildListZipSums {
  2175  			for _, m := range mg.BuildList() {
  2176  				r := resolveReplacement(loaderstate, m)
  2177  				if keepModSumsForZipSums {
  2178  					keep[modkey(r)] = true // we need the go version from the go.mod file to do anything useful with the zipfile
  2179  				}
  2180  				keep[r] = true
  2181  			}
  2182  		}
  2183  	}
  2184  
  2185  	return keep
  2186  }
  2187  
  2188  type whichSums int8
  2189  
  2190  const (
  2191  	loadedZipSumsOnly = whichSums(iota)
  2192  	addBuildListZipSums
  2193  )
  2194  
  2195  // modkey returns the module.Version under which the checksum for m's go.mod
  2196  // file is stored in the go.sum file.
  2197  func modkey(m module.Version) module.Version {
  2198  	return module.Version{Path: m.Path, Version: m.Version + "/go.mod"}
  2199  }
  2200  
  2201  func suggestModulePath(path string) string {
  2202  	var m string
  2203  
  2204  	i := len(path)
  2205  	for i > 0 && ('0' <= path[i-1] && path[i-1] <= '9' || path[i-1] == '.') {
  2206  		i--
  2207  	}
  2208  	url := path[:i]
  2209  	url = strings.TrimSuffix(url, "/v")
  2210  	url = strings.TrimSuffix(url, "/")
  2211  
  2212  	f := func(c rune) bool {
  2213  		return c > '9' || c < '0'
  2214  	}
  2215  	s := strings.FieldsFunc(path[i:], f)
  2216  	if len(s) > 0 {
  2217  		m = s[0]
  2218  	}
  2219  	m = strings.TrimLeft(m, "0")
  2220  	if m == "" || m == "1" {
  2221  		return url + "/v2"
  2222  	}
  2223  
  2224  	return url + "/v" + m
  2225  }
  2226  
  2227  func suggestGopkgIn(path string) string {
  2228  	var m string
  2229  	i := len(path)
  2230  	for i > 0 && (('0' <= path[i-1] && path[i-1] <= '9') || (path[i-1] == '.')) {
  2231  		i--
  2232  	}
  2233  	url := path[:i]
  2234  	url = strings.TrimSuffix(url, ".v")
  2235  	url = strings.TrimSuffix(url, "/v")
  2236  	url = strings.TrimSuffix(url, "/")
  2237  
  2238  	f := func(c rune) bool {
  2239  		return c > '9' || c < '0'
  2240  	}
  2241  	s := strings.FieldsFunc(path, f)
  2242  	if len(s) > 0 {
  2243  		m = s[0]
  2244  	}
  2245  
  2246  	m = strings.TrimLeft(m, "0")
  2247  
  2248  	if m == "" {
  2249  		return url + ".v1"
  2250  	}
  2251  	return url + ".v" + m
  2252  }
  2253  
  2254  func CheckGodebug(verb, k, v string) error {
  2255  	if strings.ContainsAny(k, " \t") {
  2256  		return fmt.Errorf("key contains space")
  2257  	}
  2258  	if strings.ContainsAny(v, " \t") {
  2259  		return fmt.Errorf("value contains space")
  2260  	}
  2261  	if strings.ContainsAny(k, ",") {
  2262  		return fmt.Errorf("key contains comma")
  2263  	}
  2264  	if strings.ContainsAny(v, ",") {
  2265  		return fmt.Errorf("value contains comma")
  2266  	}
  2267  	if k == "default" {
  2268  		if !strings.HasPrefix(v, "go") || !gover.IsValid(v[len("go"):]) {
  2269  			return fmt.Errorf("value for default= must be goVERSION")
  2270  		}
  2271  		if gover.Compare(v[len("go"):], gover.Local()) > 0 {
  2272  			return fmt.Errorf("default=%s too new (toolchain is go%s)", v, gover.Local())
  2273  		}
  2274  		return nil
  2275  	}
  2276  	if godebugs.Lookup(k) != nil {
  2277  		return nil
  2278  	}
  2279  	for _, info := range godebugs.Removed {
  2280  		if info.Name == k {
  2281  			return fmt.Errorf("use of removed %s %q, see https://go.dev/doc/godebug#go-1%v", verb, k, info.Removed)
  2282  		}
  2283  	}
  2284  	return fmt.Errorf("unknown %s %q", verb, k)
  2285  }
  2286  

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