// Copyright 2020 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package fs_test import ( "errors" . "io/fs" "testing" ) type subOnly struct{ SubFS } func (subOnly) Open(name string) (File, error) { return nil, ErrNotExist } func TestSub(t *testing.T) { check := func(desc string, sub FS, err error) { t.Helper() if err != nil { t.Errorf("Sub(sub): %v", err) return } data, err := ReadFile(sub, "goodbye.txt") if string(data) != "goodbye, world" || err != nil { t.Errorf(`ReadFile(%s, "goodbye.txt" = %q, %v, want %q, nil`, desc, string(data), err, "goodbye, world") } dirs, err := ReadDir(sub, ".") if err != nil || len(dirs) != 1 || dirs[0].Name() != "goodbye.txt" { var names []string for _, d := range dirs { names = append(names, d.Name()) } t.Errorf(`ReadDir(%s, ".") = %v, %v, want %v, nil`, desc, names, err, []string{"goodbye.txt"}) } } // Test that Sub uses the method when present. sub, err := Sub(subOnly{testFsys}, "sub") check("subOnly", sub, err) // Test that Sub uses Open when the method is not present. sub, err = Sub(openOnly{testFsys}, "sub") check("openOnly", sub, err) _, err = sub.Open("nonexist") if err == nil { t.Fatal("Open(nonexist): succeeded") } pe, ok := err.(*PathError) if !ok { t.Fatalf("Open(nonexist): error is %T, want *PathError", err) } if pe.Path != "nonexist" { t.Fatalf("Open(nonexist): err.Path = %q, want %q", pe.Path, "nonexist") } _, err = sub.Open("./") if !errors.Is(err, ErrInvalid) { t.Fatalf("Open(./): error is %v, want %v", err, ErrInvalid) } }