testing/fstest: return structured errors in TestFS
TestFS now returns a structured error built with errors.Join to allow to
inspect errors using errors.Is and errors.As.
All errors are now wrapped using fmt.Errorf and %w.
Fixes #63675.
Change-Id: I8fc3363f8ae70085af4afdb84c16be9ca70d7731
Reviewed-on: https://go-review.googlesource.com/c/go/+/537015
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
diff --git a/doc/next/6-stdlib/99-minor/testing/fstest/63675.md b/doc/next/6-stdlib/99-minor/testing/fstest/63675.md
new file mode 100644
index 0000000..1a3552d
--- /dev/null
+++ b/doc/next/6-stdlib/99-minor/testing/fstest/63675.md
@@ -0,0 +1,4 @@
+[`TestFS`](/pkg/testing/fstest#TestFS) now returns a structured
+error that can be unwrapped (via method `Unwrap() []error`). This allows
+inspecting errors using [`errors.Is`](/pkg/errors#Is) or
+[`errors.As`](/pkg/errors#As).
diff --git a/src/testing/fstest/testfs.go b/src/testing/fstest/testfs.go
index 78b0b82..0fd7d48 100644
--- a/src/testing/fstest/testfs.go
+++ b/src/testing/fstest/testfs.go
@@ -25,8 +25,8 @@
// Otherwise, fsys must contain at least the listed files; it can also contain others.
// The contents of fsys must not change concurrently with TestFS.
//
-// If TestFS finds any misbehaviors, it returns an error reporting all of them.
-// The error text spans multiple lines, one per detected misbehavior.
+// If TestFS finds any misbehaviors, it returns either the first error or a
+// list of errors. Use [errors.Is] or [errors.As] to inspect.
//
// Typical usage inside a test is:
//
@@ -51,7 +51,7 @@
return err
}
if err := testFS(sub, subExpected...); err != nil {
- return fmt.Errorf("testing fs.Sub(fsys, %s): %v", dir, err)
+ return fmt.Errorf("testing fs.Sub(fsys, %s): %w", dir, err)
}
break // one sub-test is enough
}
@@ -89,32 +89,29 @@
t.errorf("expected but not found: %s", name)
}
}
- if len(t.errText) == 0 {
+ if len(t.errors) == 0 {
return nil
}
- return errors.New("TestFS found errors:\n" + string(t.errText))
+ return fmt.Errorf("TestFS found errors:\n%w", errors.Join(t.errors...))
}
// An fsTester holds state for running the test.
type fsTester struct {
- fsys fs.FS
- errText []byte
- dirs []string
- files []string
+ fsys fs.FS
+ errors []error
+ dirs []string
+ files []string
}
-// errorf adds an error line to errText.
+// errorf adds an error to the list of errors.
func (t *fsTester) errorf(format string, args ...any) {
- if len(t.errText) > 0 {
- t.errText = append(t.errText, '\n')
- }
- t.errText = append(t.errText, fmt.Sprintf(format, args...)...)
+ t.errors = append(t.errors, fmt.Errorf(format, args...))
}
func (t *fsTester) openDir(dir string) fs.ReadDirFile {
f, err := t.fsys.Open(dir)
if err != nil {
- t.errorf("%s: Open: %v", dir, err)
+ t.errorf("%s: Open: %w", dir, err)
return nil
}
d, ok := f.(fs.ReadDirFile)
@@ -138,7 +135,7 @@
list, err := d.ReadDir(-1)
if err != nil {
d.Close()
- t.errorf("%s: ReadDir(-1): %v", dir, err)
+ t.errorf("%s: ReadDir(-1): %w", dir, err)
return
}
@@ -176,7 +173,7 @@
list2, err := d.ReadDir(-1)
if len(list2) > 0 || err != nil {
d.Close()
- t.errorf("%s: ReadDir(-1) at EOF = %d entries, %v, wanted 0 entries, nil", dir, len(list2), err)
+ t.errorf("%s: ReadDir(-1) at EOF = %d entries, %w, wanted 0 entries, nil", dir, len(list2), err)
return
}
@@ -184,13 +181,13 @@
list2, err = d.ReadDir(1)
if len(list2) > 0 || err != io.EOF {
d.Close()
- t.errorf("%s: ReadDir(1) at EOF = %d entries, %v, wanted 0 entries, EOF", dir, len(list2), err)
+ t.errorf("%s: ReadDir(1) at EOF = %d entries, %w, wanted 0 entries, EOF", dir, len(list2), err)
return
}
// Check that close does not report an error.
if err := d.Close(); err != nil {
- t.errorf("%s: Close: %v", dir, err)
+ t.errorf("%s: Close: %w", dir, err)
}
// Check that closing twice doesn't crash.
@@ -204,7 +201,7 @@
defer d.Close()
list2, err = d.ReadDir(-1)
if err != nil {
- t.errorf("%s: second Open+ReadDir(-1): %v", dir, err)
+ t.errorf("%s: second Open+ReadDir(-1): %w", dir, err)
return
}
t.checkDirList(dir, "first Open+ReadDir(-1) vs second Open+ReadDir(-1)", list, list2)
@@ -230,7 +227,7 @@
break
}
if err != nil {
- t.errorf("%s: third Open: ReadDir(%d) after %d: %v", dir, n, len(list2), err)
+ t.errorf("%s: third Open: ReadDir(%d) after %d: %w", dir, n, len(list2), err)
return
}
if n == 0 {
@@ -244,7 +241,7 @@
if fsys, ok := t.fsys.(fs.ReadDirFS); ok {
list2, err := fsys.ReadDir(dir)
if err != nil {
- t.errorf("%s: fsys.ReadDir: %v", dir, err)
+ t.errorf("%s: fsys.ReadDir: %w", dir, err)
return
}
t.checkDirList(dir, "first Open+ReadDir(-1) vs fsys.ReadDir", list, list2)
@@ -259,7 +256,7 @@
// Check fs.ReadDir as well.
list2, err = fs.ReadDir(t.fsys, dir)
if err != nil {
- t.errorf("%s: fs.ReadDir: %v", dir, err)
+ t.errorf("%s: fs.ReadDir: %w", dir, err)
return
}
t.checkDirList(dir, "first Open+ReadDir(-1) vs fs.ReadDir", list, list2)
@@ -358,7 +355,7 @@
names, err := t.fsys.(fs.GlobFS).Glob(glob)
if err != nil {
- t.errorf("%s: Glob(%#q): %v", dir, glob, err)
+ t.errorf("%s: Glob(%#q): %w", dir, glob, err)
return
}
if reflect.DeepEqual(want, names) {
@@ -391,13 +388,13 @@
func (t *fsTester) checkStat(path string, entry fs.DirEntry) {
file, err := t.fsys.Open(path)
if err != nil {
- t.errorf("%s: Open: %v", path, err)
+ t.errorf("%s: Open: %w", path, err)
return
}
info, err := file.Stat()
file.Close()
if err != nil {
- t.errorf("%s: Stat: %v", path, err)
+ t.errorf("%s: Stat: %w", path, err)
return
}
fentry := formatEntry(entry)
@@ -409,7 +406,7 @@
einfo, err := entry.Info()
if err != nil {
- t.errorf("%s: entry.Info: %v", path, err)
+ t.errorf("%s: entry.Info: %w", path, err)
return
}
finfo := formatInfo(info)
@@ -430,7 +427,7 @@
// Stat should be the same as Open+Stat, even for symlinks.
info2, err := fs.Stat(t.fsys, path)
if err != nil {
- t.errorf("%s: fs.Stat: %v", path, err)
+ t.errorf("%s: fs.Stat: %w", path, err)
return
}
finfo2 := formatInfo(info2)
@@ -441,7 +438,7 @@
if fsys, ok := t.fsys.(fs.StatFS); ok {
info2, err := fsys.Stat(path)
if err != nil {
- t.errorf("%s: fsys.Stat: %v", path, err)
+ t.errorf("%s: fsys.Stat: %w", path, err)
return
}
finfo2 := formatInfo(info2)
@@ -508,19 +505,19 @@
// Read entire file.
f, err := t.fsys.Open(file)
if err != nil {
- t.errorf("%s: Open: %v", file, err)
+ t.errorf("%s: Open: %w", file, err)
return
}
data, err := io.ReadAll(f)
if err != nil {
f.Close()
- t.errorf("%s: Open+ReadAll: %v", file, err)
+ t.errorf("%s: Open+ReadAll: %w", file, err)
return
}
if err := f.Close(); err != nil {
- t.errorf("%s: Close: %v", file, err)
+ t.errorf("%s: Close: %w", file, err)
}
// Check that closing twice doesn't crash.
@@ -531,7 +528,7 @@
if fsys, ok := t.fsys.(fs.ReadFileFS); ok {
data2, err := fsys.ReadFile(file)
if err != nil {
- t.errorf("%s: fsys.ReadFile: %v", file, err)
+ t.errorf("%s: fsys.ReadFile: %w", file, err)
return
}
t.checkFileRead(file, "ReadAll vs fsys.ReadFile", data, data2)
@@ -543,7 +540,7 @@
}
data2, err = fsys.ReadFile(file)
if err != nil {
- t.errorf("%s: second call to fsys.ReadFile: %v", file, err)
+ t.errorf("%s: second call to fsys.ReadFile: %w", file, err)
return
}
t.checkFileRead(file, "Readall vs second fsys.ReadFile", data, data2)
@@ -555,7 +552,7 @@
// Check that fs.ReadFile works with t.fsys.
data2, err := fs.ReadFile(t.fsys, file)
if err != nil {
- t.errorf("%s: fs.ReadFile: %v", file, err)
+ t.errorf("%s: fs.ReadFile: %w", file, err)
return
}
t.checkFileRead(file, "ReadAll vs fs.ReadFile", data, data2)
@@ -563,7 +560,7 @@
// Use iotest.TestReader to check small reads, Seek, ReadAt.
f, err = t.fsys.Open(file)
if err != nil {
- t.errorf("%s: second Open: %v", file, err)
+ t.errorf("%s: second Open: %w", file, err)
return
}
defer f.Close()
diff --git a/src/testing/fstest/testfs_test.go b/src/testing/fstest/testfs_test.go
index a48c597..b9f10c6 100644
--- a/src/testing/fstest/testfs_test.go
+++ b/src/testing/fstest/testfs_test.go
@@ -5,6 +5,7 @@
package fstest
import (
+ "errors"
"internal/testenv"
"io/fs"
"os"
@@ -76,3 +77,40 @@
t.Error(err)
}
}
+
+// failPermFS is a filesystem that always fails with fs.ErrPermission.
+type failPermFS struct{}
+
+func (f failPermFS) Open(name string) (fs.File, error) {
+ if !fs.ValidPath(name) {
+ return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrInvalid}
+ }
+ return nil, &fs.PathError{Op: "open", Path: name, Err: fs.ErrPermission}
+}
+
+func TestTestFSWrappedErrors(t *testing.T) {
+ err := TestFS(failPermFS{})
+ if err == nil {
+ t.Fatal("error expected")
+ }
+ t.Logf("Error (expecting wrapped fs.ErrPermission):\n%v", err)
+
+ if !errors.Is(err, fs.ErrPermission) {
+ t.Errorf("error should be a wrapped ErrPermission: %#v", err)
+ }
+
+ // TestFS is expected to return a list of errors.
+ // Enforce that the list can be extracted for browsing.
+ var errs interface{ Unwrap() []error }
+ if !errors.As(err, &errs) {
+ t.Errorf("caller should be able to extract the errors as a list: %#v", err)
+ } else {
+ for _, err := range errs.Unwrap() {
+ // ErrPermission is expected
+ // but any other error must be reported.
+ if !errors.Is(err, fs.ErrPermission) {
+ t.Errorf("unexpected error: %v", err)
+ }
+ }
+ }
+}
