testfs.go

     1  // Copyright 2020 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 fstest implements support for testing implementations and users of file systems.
     6  package fstest
     7  
     8  import (
     9  	"errors"
    10  	"fmt"
    11  	"io"
    12  	"io/fs"
    13  	"maps"
    14  	"path"
    15  	"slices"
    16  	"strings"
    17  	"testing/iotest"
    18  )
    19  
    20  // TestFS tests a file system implementation.
    21  // It walks the entire tree of files in fsys,
    22  // opening and checking that each file behaves correctly.
    23  // It also checks that the file system contains at least the expected files.
    24  // As a special case, if no expected files are listed, fsys must be empty.
    25  // Otherwise, fsys must contain at least the listed files; it can also contain others.
    26  // The contents of fsys must not change concurrently with TestFS.
    27  //
    28  // If TestFS finds any misbehaviors, it returns either the first error or a
    29  // list of errors. Use [errors.Is] or [errors.As] to inspect.
    30  //
    31  // Typical usage inside a test is:
    32  //
    33  //	if err := fstest.TestFS(myFS, "file/that/should/be/present"); err != nil {
    34  //		t.Fatal(err)
    35  //	}
    36  func TestFS(fsys fs.FS, expected ...string) error {
    37  	if err := testFS(fsys, expected...); err != nil {
    38  		return err
    39  	}
    40  	for _, name := range expected {
    41  		if i := strings.Index(name, "/"); i >= 0 {
    42  			dir, dirSlash := name[:i], name[:i+1]
    43  			var subExpected []string
    44  			for _, name := range expected {
    45  				if strings.HasPrefix(name, dirSlash) {
    46  					subExpected = append(subExpected, name[len(dirSlash):])
    47  				}
    48  			}
    49  			sub, err := fs.Sub(fsys, dir)
    50  			if err != nil {
    51  				return err
    52  			}
    53  			if err := testFS(sub, subExpected...); err != nil {
    54  				return fmt.Errorf("testing fs.Sub(fsys, %s): %w", dir, err)
    55  			}
    56  			break // one sub-test is enough
    57  		}
    58  	}
    59  	return nil
    60  }
    61  
    62  func testFS(fsys fs.FS, expected ...string) error {
    63  	t := fsTester{fsys: fsys}
    64  	t.checkDir(".")
    65  	t.checkOpen(".")
    66  	found := make(map[string]bool)
    67  	for _, dir := range t.dirs {
    68  		found[dir] = true
    69  	}
    70  	for _, file := range t.files {
    71  		found[file] = true
    72  	}
    73  	delete(found, ".")
    74  	if len(expected) == 0 && len(found) > 0 {
    75  		list := slices.Sorted(maps.Keys(found))
    76  		if len(list) > 15 {
    77  			list = append(list[:10], "...")
    78  		}
    79  		t.errorf("expected empty file system but found files:\n%s", strings.Join(list, "\n"))
    80  	}
    81  	for _, name := range expected {
    82  		if !found[name] {
    83  			t.errorf("expected but not found: %s", name)
    84  		}
    85  	}
    86  	if len(t.errors) == 0 {
    87  		return nil
    88  	}
    89  	return fmt.Errorf("TestFS found errors:\n%w", errors.Join(t.errors...))
    90  }
    91  
    92  // An fsTester holds state for running the test.
    93  type fsTester struct {
    94  	fsys   fs.FS
    95  	errors []error
    96  	dirs   []string
    97  	files  []string
    98  }
    99  
   100  // errorf adds an error to the list of errors.
   101  func (t *fsTester) errorf(format string, args ...any) {
   102  	t.errors = append(t.errors, fmt.Errorf(format, args...))
   103  }
   104  
   105  func (t *fsTester) openDir(dir string) fs.ReadDirFile {
   106  	f, err := t.fsys.Open(dir)
   107  	if err != nil {
   108  		t.errorf("%s: Open: %w", dir, err)
   109  		return nil
   110  	}
   111  	d, ok := f.(fs.ReadDirFile)
   112  	if !ok {
   113  		f.Close()
   114  		t.errorf("%s: Open returned File type %T, not a fs.ReadDirFile", dir, f)
   115  		return nil
   116  	}
   117  	return d
   118  }
   119  
   120  // checkDir checks the directory dir, which is expected to exist
   121  // (it is either the root or was found in a directory listing with IsDir true).
   122  func (t *fsTester) checkDir(dir string) {
   123  	// Read entire directory.
   124  	t.dirs = append(t.dirs, dir)
   125  	d := t.openDir(dir)
   126  	if d == nil {
   127  		return
   128  	}
   129  	list, err := d.ReadDir(-1)
   130  	if err != nil {
   131  		d.Close()
   132  		t.errorf("%s: ReadDir(-1): %w", dir, err)
   133  		return
   134  	}
   135  
   136  	// Check all children.
   137  	var prefix string
   138  	if dir == "." {
   139  		prefix = ""
   140  	} else {
   141  		prefix = dir + "/"
   142  	}
   143  	for _, info := range list {
   144  		name := info.Name()
   145  		switch {
   146  		case name == ".", name == "..", name == "":
   147  			t.errorf("%s: ReadDir: child has invalid name: %#q", dir, name)
   148  			continue
   149  		case strings.Contains(name, "/"):
   150  			t.errorf("%s: ReadDir: child name contains slash: %#q", dir, name)
   151  			continue
   152  		case strings.Contains(name, `\`):
   153  			t.errorf("%s: ReadDir: child name contains backslash: %#q", dir, name)
   154  			continue
   155  		}
   156  		path := prefix + name
   157  		t.checkStat(path, info)
   158  		t.checkOpen(path)
   159  		if info.IsDir() {
   160  			t.checkDir(path)
   161  		} else {
   162  			t.checkFile(path)
   163  		}
   164  	}
   165  
   166  	// Check ReadDir(-1) at EOF.
   167  	list2, err := d.ReadDir(-1)
   168  	if len(list2) > 0 || err != nil {
   169  		d.Close()
   170  		t.errorf("%s: ReadDir(-1) at EOF = %d entries, %w, wanted 0 entries, nil", dir, len(list2), err)
   171  		return
   172  	}
   173  
   174  	// Check ReadDir(1) at EOF (different results).
   175  	list2, err = d.ReadDir(1)
   176  	if len(list2) > 0 || err != io.EOF {
   177  		d.Close()
   178  		t.errorf("%s: ReadDir(1) at EOF = %d entries, %w, wanted 0 entries, EOF", dir, len(list2), err)
   179  		return
   180  	}
   181  
   182  	// Check that close does not report an error.
   183  	if err := d.Close(); err != nil {
   184  		t.errorf("%s: Close: %w", dir, err)
   185  	}
   186  
   187  	// Check that closing twice doesn't crash.
   188  	// The return value doesn't matter.
   189  	d.Close()
   190  
   191  	// Reopen directory, read a second time, make sure contents match.
   192  	if d = t.openDir(dir); d == nil {
   193  		return
   194  	}
   195  	defer d.Close()
   196  	list2, err = d.ReadDir(-1)
   197  	if err != nil {
   198  		t.errorf("%s: second Open+ReadDir(-1): %w", dir, err)
   199  		return
   200  	}
   201  	t.checkDirList(dir, "first Open+ReadDir(-1) vs second Open+ReadDir(-1)", list, list2)
   202  
   203  	// Reopen directory, read a third time in pieces, make sure contents match.
   204  	if d = t.openDir(dir); d == nil {
   205  		return
   206  	}
   207  	defer d.Close()
   208  	list2 = nil
   209  	for {
   210  		n := 1
   211  		if len(list2) > 0 {
   212  			n = 2
   213  		}
   214  		frag, err := d.ReadDir(n)
   215  		if len(frag) > n {
   216  			t.errorf("%s: third Open: ReadDir(%d) after %d: %d entries (too many)", dir, n, len(list2), len(frag))
   217  			return
   218  		}
   219  		list2 = append(list2, frag...)
   220  		if err == io.EOF {
   221  			break
   222  		}
   223  		if err != nil {
   224  			t.errorf("%s: third Open: ReadDir(%d) after %d: %w", dir, n, len(list2), err)
   225  			return
   226  		}
   227  		if n == 0 {
   228  			t.errorf("%s: third Open: ReadDir(%d) after %d: 0 entries but nil error", dir, n, len(list2))
   229  			return
   230  		}
   231  	}
   232  	t.checkDirList(dir, "first Open+ReadDir(-1) vs third Open+ReadDir(1,2) loop", list, list2)
   233  
   234  	// If fsys has ReadDir, check that it matches and is sorted.
   235  	if fsys, ok := t.fsys.(fs.ReadDirFS); ok {
   236  		list2, err := fsys.ReadDir(dir)
   237  		if err != nil {
   238  			t.errorf("%s: fsys.ReadDir: %w", dir, err)
   239  			return
   240  		}
   241  		t.checkDirList(dir, "first Open+ReadDir(-1) vs fsys.ReadDir", list, list2)
   242  
   243  		for i := 0; i+1 < len(list2); i++ {
   244  			if list2[i].Name() >= list2[i+1].Name() {
   245  				t.errorf("%s: fsys.ReadDir: list not sorted: %s before %s", dir, list2[i].Name(), list2[i+1].Name())
   246  			}
   247  		}
   248  	}
   249  
   250  	// Check fs.ReadDir as well.
   251  	list2, err = fs.ReadDir(t.fsys, dir)
   252  	if err != nil {
   253  		t.errorf("%s: fs.ReadDir: %w", dir, err)
   254  		return
   255  	}
   256  	t.checkDirList(dir, "first Open+ReadDir(-1) vs fs.ReadDir", list, list2)
   257  
   258  	for i := 0; i+1 < len(list2); i++ {
   259  		if list2[i].Name() >= list2[i+1].Name() {
   260  			t.errorf("%s: fs.ReadDir: list not sorted: %s before %s", dir, list2[i].Name(), list2[i+1].Name())
   261  		}
   262  	}
   263  
   264  	t.checkGlob(dir, list2)
   265  }
   266  
   267  // formatEntry formats an fs.DirEntry into a string for error messages and comparison.
   268  func formatEntry(entry fs.DirEntry) string {
   269  	return fmt.Sprintf("%s IsDir=%v Type=%v", entry.Name(), entry.IsDir(), entry.Type())
   270  }
   271  
   272  // formatInfoEntry formats an fs.FileInfo into a string like the result of formatEntry, for error messages and comparison.
   273  func formatInfoEntry(info fs.FileInfo) string {
   274  	return fmt.Sprintf("%s IsDir=%v Type=%v", info.Name(), info.IsDir(), info.Mode().Type())
   275  }
   276  
   277  // formatInfo formats an fs.FileInfo into a string for error messages and comparison.
   278  func formatInfo(info fs.FileInfo) string {
   279  	return fmt.Sprintf("%s IsDir=%v Mode=%v Size=%d ModTime=%v", info.Name(), info.IsDir(), info.Mode(), info.Size(), info.ModTime())
   280  }
   281  
   282  // checkGlob checks that various glob patterns work if the file system implements GlobFS.
   283  func (t *fsTester) checkGlob(dir string, list []fs.DirEntry) {
   284  	if _, ok := t.fsys.(fs.GlobFS); !ok {
   285  		return
   286  	}
   287  
   288  	// Make a complex glob pattern prefix that only matches dir.
   289  	var glob string
   290  	if dir != "." {
   291  		elem := strings.Split(dir, "/")
   292  		for i, e := range elem {
   293  			var pattern []rune
   294  			for j, r := range e {
   295  				if r == '*' || r == '?' || r == '\\' || r == '[' || r == '-' {
   296  					pattern = append(pattern, '\\', r)
   297  					continue
   298  				}
   299  				switch (i + j) % 5 {
   300  				case 0:
   301  					pattern = append(pattern, r)
   302  				case 1:
   303  					pattern = append(pattern, '[', r, ']')
   304  				case 2:
   305  					pattern = append(pattern, '[', r, '-', r, ']')
   306  				case 3:
   307  					pattern = append(pattern, '[', '\\', r, ']')
   308  				case 4:
   309  					pattern = append(pattern, '[', '\\', r, '-', '\\', r, ']')
   310  				}
   311  			}
   312  			elem[i] = string(pattern)
   313  		}
   314  		glob = strings.Join(elem, "/") + "/"
   315  	}
   316  
   317  	// Test that malformed patterns are detected.
   318  	// The error is likely path.ErrBadPattern but need not be.
   319  	if _, err := t.fsys.(fs.GlobFS).Glob(glob + "nonexist/[]"); err == nil {
   320  		t.errorf("%s: Glob(%#q): bad pattern not detected", dir, glob+"nonexist/[]")
   321  	}
   322  
   323  	// Try to find a letter that appears in only some of the final names.
   324  	c := rune('a')
   325  	for ; c <= 'z'; c++ {
   326  		have, haveNot := false, false
   327  		for _, d := range list {
   328  			if strings.ContainsRune(d.Name(), c) {
   329  				have = true
   330  			} else {
   331  				haveNot = true
   332  			}
   333  		}
   334  		if have && haveNot {
   335  			break
   336  		}
   337  	}
   338  	if c > 'z' {
   339  		c = 'a'
   340  	}
   341  	glob += "*" + string(c) + "*"
   342  
   343  	var want []string
   344  	for _, d := range list {
   345  		if strings.ContainsRune(d.Name(), c) {
   346  			want = append(want, path.Join(dir, d.Name()))
   347  		}
   348  	}
   349  
   350  	names, err := t.fsys.(fs.GlobFS).Glob(glob)
   351  	if err != nil {
   352  		t.errorf("%s: Glob(%#q): %w", dir, glob, err)
   353  		return
   354  	}
   355  	if slices.Equal(want, names) {
   356  		return
   357  	}
   358  
   359  	if !slices.IsSorted(names) {
   360  		t.errorf("%s: Glob(%#q): unsorted output:\n%s", dir, glob, strings.Join(names, "\n"))
   361  		slices.Sort(names)
   362  	}
   363  
   364  	var problems []string
   365  	for len(want) > 0 || len(names) > 0 {
   366  		switch {
   367  		case len(want) > 0 && len(names) > 0 && want[0] == names[0]:
   368  			want, names = want[1:], names[1:]
   369  		case len(want) > 0 && (len(names) == 0 || want[0] < names[0]):
   370  			problems = append(problems, "missing: "+want[0])
   371  			want = want[1:]
   372  		default:
   373  			problems = append(problems, "extra: "+names[0])
   374  			names = names[1:]
   375  		}
   376  	}
   377  	t.errorf("%s: Glob(%#q): wrong output:\n%s", dir, glob, strings.Join(problems, "\n"))
   378  }
   379  
   380  // checkStat checks that a direct stat of path matches entry,
   381  // which was found in the parent's directory listing.
   382  func (t *fsTester) checkStat(path string, entry fs.DirEntry) {
   383  	file, err := t.fsys.Open(path)
   384  	if err != nil {
   385  		t.errorf("%s: Open: %w", path, err)
   386  		return
   387  	}
   388  	info, err := file.Stat()
   389  	file.Close()
   390  	if err != nil {
   391  		t.errorf("%s: Stat: %w", path, err)
   392  		return
   393  	}
   394  	fentry := formatEntry(entry)
   395  	fientry := formatInfoEntry(info)
   396  	// Note: mismatch here is OK for symlink, because Open dereferences symlink.
   397  	if fentry != fientry && entry.Type()&fs.ModeSymlink == 0 {
   398  		t.errorf("%s: mismatch:\n\tentry = %s\n\tfile.Stat() = %s", path, fentry, fientry)
   399  	}
   400  
   401  	einfo, err := entry.Info()
   402  	if err != nil {
   403  		t.errorf("%s: entry.Info: %w", path, err)
   404  		return
   405  	}
   406  	finfo := formatInfo(info)
   407  	if entry.Type()&fs.ModeSymlink != 0 {
   408  		// For symlink, just check that entry.Info matches entry on common fields.
   409  		// Open deferences symlink, so info itself may differ.
   410  		feentry := formatInfoEntry(einfo)
   411  		if fentry != feentry {
   412  			t.errorf("%s: mismatch\n\tentry = %s\n\tentry.Info() = %s\n", path, fentry, feentry)
   413  		}
   414  	} else {
   415  		feinfo := formatInfo(einfo)
   416  		if feinfo != finfo {
   417  			t.errorf("%s: mismatch:\n\tentry.Info() = %s\n\tfile.Stat() = %s\n", path, feinfo, finfo)
   418  		}
   419  	}
   420  
   421  	// Stat should be the same as Open+Stat, even for symlinks.
   422  	info2, err := fs.Stat(t.fsys, path)
   423  	if err != nil {
   424  		t.errorf("%s: fs.Stat: %w", path, err)
   425  		return
   426  	}
   427  	finfo2 := formatInfo(info2)
   428  	if finfo2 != finfo {
   429  		t.errorf("%s: fs.Stat(...) = %s\n\twant %s", path, finfo2, finfo)
   430  	}
   431  
   432  	if fsys, ok := t.fsys.(fs.StatFS); ok {
   433  		info2, err := fsys.Stat(path)
   434  		if err != nil {
   435  			t.errorf("%s: fsys.Stat: %w", path, err)
   436  			return
   437  		}
   438  		finfo2 := formatInfo(info2)
   439  		if finfo2 != finfo {
   440  			t.errorf("%s: fsys.Stat(...) = %s\n\twant %s", path, finfo2, finfo)
   441  		}
   442  	}
   443  }
   444  
   445  // checkDirList checks that two directory lists contain the same files and file info.
   446  // The order of the lists need not match.
   447  func (t *fsTester) checkDirList(dir, desc string, list1, list2 []fs.DirEntry) {
   448  	old := make(map[string]fs.DirEntry)
   449  	checkMode := func(entry fs.DirEntry) {
   450  		if entry.IsDir() != (entry.Type()&fs.ModeDir != 0) {
   451  			if entry.IsDir() {
   452  				t.errorf("%s: ReadDir returned %s with IsDir() = true, Type() & ModeDir = 0", dir, entry.Name())
   453  			} else {
   454  				t.errorf("%s: ReadDir returned %s with IsDir() = false, Type() & ModeDir = ModeDir", dir, entry.Name())
   455  			}
   456  		}
   457  	}
   458  
   459  	for _, entry1 := range list1 {
   460  		old[entry1.Name()] = entry1
   461  		checkMode(entry1)
   462  	}
   463  
   464  	var diffs []string
   465  	for _, entry2 := range list2 {
   466  		entry1 := old[entry2.Name()]
   467  		if entry1 == nil {
   468  			checkMode(entry2)
   469  			diffs = append(diffs, "+ "+formatEntry(entry2))
   470  			continue
   471  		}
   472  		if formatEntry(entry1) != formatEntry(entry2) {
   473  			diffs = append(diffs, "- "+formatEntry(entry1), "+ "+formatEntry(entry2))
   474  		}
   475  		delete(old, entry2.Name())
   476  	}
   477  	for _, entry1 := range old {
   478  		diffs = append(diffs, "- "+formatEntry(entry1))
   479  	}
   480  
   481  	if len(diffs) == 0 {
   482  		return
   483  	}
   484  
   485  	slices.SortFunc(diffs, func(a, b string) int {
   486  		fa := strings.Fields(a)
   487  		fb := strings.Fields(b)
   488  		// sort by name (i < j) and then +/- (j < i, because + < -)
   489  		return strings.Compare(fa[1]+" "+fb[0], fb[1]+" "+fa[0])
   490  	})
   491  
   492  	t.errorf("%s: diff %s:\n\t%s", dir, desc, strings.Join(diffs, "\n\t"))
   493  }
   494  
   495  // checkFile checks that basic file reading works correctly.
   496  func (t *fsTester) checkFile(file string) {
   497  	t.files = append(t.files, file)
   498  
   499  	// Read entire file.
   500  	f, err := t.fsys.Open(file)
   501  	if err != nil {
   502  		t.errorf("%s: Open: %w", file, err)
   503  		return
   504  	}
   505  
   506  	data, err := io.ReadAll(f)
   507  	if err != nil {
   508  		f.Close()
   509  		t.errorf("%s: Open+ReadAll: %w", file, err)
   510  		return
   511  	}
   512  
   513  	if err := f.Close(); err != nil {
   514  		t.errorf("%s: Close: %w", file, err)
   515  	}
   516  
   517  	// Check that closing twice doesn't crash.
   518  	// The return value doesn't matter.
   519  	f.Close()
   520  
   521  	// Check that ReadFile works if present.
   522  	if fsys, ok := t.fsys.(fs.ReadFileFS); ok {
   523  		data2, err := fsys.ReadFile(file)
   524  		if err != nil {
   525  			t.errorf("%s: fsys.ReadFile: %w", file, err)
   526  			return
   527  		}
   528  		t.checkFileRead(file, "ReadAll vs fsys.ReadFile", data, data2)
   529  
   530  		// Modify the data and check it again. Modifying the
   531  		// returned byte slice should not affect the next call.
   532  		for i := range data2 {
   533  			data2[i]++
   534  		}
   535  		data2, err = fsys.ReadFile(file)
   536  		if err != nil {
   537  			t.errorf("%s: second call to fsys.ReadFile: %w", file, err)
   538  			return
   539  		}
   540  		t.checkFileRead(file, "Readall vs second fsys.ReadFile", data, data2)
   541  
   542  		t.checkBadPath(file, "ReadFile",
   543  			func(name string) error { _, err := fsys.ReadFile(name); return err })
   544  	}
   545  
   546  	// Check that fs.ReadFile works with t.fsys.
   547  	data2, err := fs.ReadFile(t.fsys, file)
   548  	if err != nil {
   549  		t.errorf("%s: fs.ReadFile: %w", file, err)
   550  		return
   551  	}
   552  	t.checkFileRead(file, "ReadAll vs fs.ReadFile", data, data2)
   553  
   554  	// Use iotest.TestReader to check small reads, Seek, ReadAt.
   555  	f, err = t.fsys.Open(file)
   556  	if err != nil {
   557  		t.errorf("%s: second Open: %w", file, err)
   558  		return
   559  	}
   560  	defer f.Close()
   561  	if err := iotest.TestReader(f, data); err != nil {
   562  		t.errorf("%s: failed TestReader:\n\t%s", file, strings.ReplaceAll(err.Error(), "\n", "\n\t"))
   563  	}
   564  }
   565  
   566  func (t *fsTester) checkFileRead(file, desc string, data1, data2 []byte) {
   567  	if string(data1) != string(data2) {
   568  		t.errorf("%s: %s: different data returned\n\t%q\n\t%q", file, desc, data1, data2)
   569  		return
   570  	}
   571  }
   572  
   573  // checkBadPath checks that various invalid forms of file's name cannot be opened using t.fsys.Open.
   574  func (t *fsTester) checkOpen(file string) {
   575  	t.checkBadPath(file, "Open", func(file string) error {
   576  		f, err := t.fsys.Open(file)
   577  		if err == nil {
   578  			f.Close()
   579  		}
   580  		return err
   581  	})
   582  }
   583  
   584  // checkBadPath checks that various invalid forms of file's name cannot be opened using open.
   585  func (t *fsTester) checkBadPath(file string, desc string, open func(string) error) {
   586  	bad := []string{
   587  		"/" + file,
   588  		file + "/.",
   589  	}
   590  	if file == "." {
   591  		bad = append(bad, "/")
   592  	}
   593  	if i := strings.Index(file, "/"); i >= 0 {
   594  		bad = append(bad,
   595  			file[:i]+"//"+file[i+1:],
   596  			file[:i]+"/./"+file[i+1:],
   597  			file[:i]+`\`+file[i+1:],
   598  			file[:i]+"/../"+file,
   599  		)
   600  	}
   601  	if i := strings.LastIndex(file, "/"); i >= 0 {
   602  		bad = append(bad,
   603  			file[:i]+"//"+file[i+1:],
   604  			file[:i]+"/./"+file[i+1:],
   605  			file[:i]+`\`+file[i+1:],
   606  			file+"/../"+file[i+1:],
   607  		)
   608  	}
   609  
   610  	for _, b := range bad {
   611  		if err := open(b); err == nil {
   612  			t.errorf("%s: %s(%s) succeeded, want error", file, desc, b)
   613  		}
   614  	}
   615  }
   616
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