[READ-ONLY] Mirror of https://github.com/darccio/zas. Most simple static website generator in Golang.
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zas atomic_write_test.go
3.5 kB · 136 lines
Go
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import ( "errors" "io" "os" "path/filepath" "strings" "testing")
// atomicWriteFile must never truncate or partially write the final// destination path: it only ever touches a temporary file in the same// directory, renaming it onto the destination once write fully succeeds.
// assertNoStrayTempFiles confirms atomicWriteFile cleaned up after itself:// no leftover ".*.tmp" entry in dir.func assertNoStrayTempFiles(t *testing.T, dir string) { t.Helper() entries, err := os.ReadDir(dir) if err != nil { t.Fatal(err) } for _, e := range entries { if strings.HasSuffix(e.Name(), ".tmp") { t.Fatalf("stray temp file left behind in %s: %s", dir, e.Name()) } }}
func TestAtomicWriteFileLeavesExistingContentOnError(t *testing.T) { gen := &Generator{} dir := t.TempDir() path := filepath.Join(dir, "out.txt") original := "original content, must survive a failed write" if err := os.WriteFile(path, []byte(original), 0o644); err != nil { t.Fatal(err) }
wantErr := errors.New("boom") err := gen.atomicWriteFile(path, func(w io.Writer) error { if _, werr := io.WriteString(w, "partial-new-bytes-that-must-never-land"); werr != nil { return werr } return wantErr }) if !errors.Is(err, wantErr) { t.Fatalf("atomicWriteFile() error = %v, want %v", err, wantErr) }
got, err := os.ReadFile(path) if err != nil { t.Fatal(err) } if string(got) != original { t.Fatalf("destination content = %q, want untouched original %q", got, original) } assertNoStrayTempFiles(t, dir)}
func TestAtomicWriteFileLeavesNoFileOnErrorWhenAbsent(t *testing.T) { gen := &Generator{} dir := t.TempDir() path := filepath.Join(dir, "out.txt")
wantErr := errors.New("boom") err := gen.atomicWriteFile(path, func(w io.Writer) error { _, _ = io.WriteString(w, "partial-bytes-that-must-never-land") return wantErr }) if !errors.Is(err, wantErr) { t.Fatalf("atomicWriteFile() error = %v, want %v", err, wantErr) }
if _, statErr := os.Stat(path); !os.IsNotExist(statErr) { t.Fatalf("destination exists after a failed write (stat err = %v), want absent", statErr) } assertNoStrayTempFiles(t, dir)}
func TestAtomicWriteFileSuccessSetsDefaultPermissionsAndContent(t *testing.T) { gen := &Generator{} dir := t.TempDir() path := filepath.Join(dir, "out.txt") want := "hello atomic world"
err := gen.atomicWriteFile(path, func(w io.Writer) error { _, werr := io.WriteString(w, want) return werr }) if err != nil { t.Fatalf("atomicWriteFile() error = %v, want nil", err) }
info, err := os.Stat(path) if err != nil { t.Fatal(err) } if perm := info.Mode().Perm(); perm != DefaultFilePerm { t.Fatalf("permissions = %o, want %o", perm, DefaultFilePerm) } got, err := os.ReadFile(path) if err != nil { t.Fatal(err) } if string(got) != want { t.Fatalf("content = %q, want %q", got, want) } assertNoStrayTempFiles(t, dir)}
func TestAtomicWriteFileOverwritesExistingContentOnSuccess(t *testing.T) { gen := &Generator{} dir := t.TempDir() path := filepath.Join(dir, "out.txt") if err := os.WriteFile(path, []byte("stale content"), 0o644); err != nil { t.Fatal(err) }
want := "fresh content" err := gen.atomicWriteFile(path, func(w io.Writer) error { _, werr := io.WriteString(w, want) return werr }) if err != nil { t.Fatalf("atomicWriteFile() error = %v, want nil", err) } got, err := os.ReadFile(path) if err != nil { t.Fatal(err) } if string(got) != want { t.Fatalf("content = %q, want %q", got, want) } assertNoStrayTempFiles(t, dir)}