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

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