testing: implement testing.TempDir

src/testing/testing.go

@@ -15,6 +15,8 @@ import (
 	"io"
 	"os"
 	"strings"
+	"unicode"
+	"unicode/utf8"
 )
 
 // Testing flags.
@@ -54,6 +56,10 @@ type common struct {
 	parent *common
 	level  int    // Nesting depth of test or benchmark.
 	name   string // Name of test or benchmark.
+
+ 	tempDir    string
+ 	tempDirErr error
+ 	tempDirSeq int32
 }
 
 // TB is the interface common to T and B.
@@ -216,6 +222,70 @@ func (c *common) Cleanup(f func()) {
 	c.cleanups = append(c.cleanups, f)
 }
 
+// TempDir returns a temporary directory for the test to use.
+// The directory is automatically removed by Cleanup when the test and
+// all its subtests complete.
+// Each subsequent call to t.TempDir returns a unique directory;
+// if the directory creation fails, TempDir terminates the test by calling Fatal.
+func (c *common) TempDir() string {
+	// Use a single parent directory for all the temporary directories
+	// created by a test, each numbered sequentially.
+	var nonExistent bool
+	if c.tempDir == "" { // Usually the case with js/wasm
+		nonExistent = true
+	} else {
+		_, err := os.Stat(c.tempDir)
+		nonExistent = os.IsNotExist(err)
+		if err != nil && !nonExistent {
+			c.Fatalf("TempDir: %v", err)
+		}
+	}
+
+	if nonExistent {
+		c.Helper()
+
+		// Drop unusual characters (such as path separators or
+		// characters interacting with globs) from the directory name to
+		// avoid surprising os.MkdirTemp behavior.
+		mapper := func(r rune) rune {
+			if r < utf8.RuneSelf {
+				const allowed = "!#$%&()+,-.=@^_{}~ "
+				if '0' <= r && r <= '9' ||
+					'a' <= r && r <= 'z' ||
+					'A' <= r && r <= 'Z' {
+					return r
+				}
+				if strings.ContainsRune(allowed, r) {
+					return r
+				}
+			} else if unicode.IsLetter(r) || unicode.IsNumber(r) {
+				return r
+			}
+			return -1
+		}
+		pattern := strings.Map(mapper, c.Name())
+		c.tempDir, c.tempDirErr = os.MkdirTemp("", pattern)
+		if c.tempDirErr == nil {
+			c.Cleanup(func() {
+				if err := os.RemoveAll(c.tempDir); err != nil {
+					c.Errorf("TempDir RemoveAll cleanup: %v", err)
+				}
+			})
+		}
+	}
+
+	if c.tempDirErr != nil {
+		c.Fatalf("TempDir: %v", c.tempDirErr)
+	}
+	seq := c.tempDirSeq
+	c.tempDirSeq++
+	dir := fmt.Sprintf("%s%c%03d", c.tempDir, os.PathSeparator, seq)
+	if err := os.Mkdir(dir, 0777); err != nil {
+		c.Fatalf("TempDir: %v", err)
+	}
+	return dir
+}
+
 // runCleanup is called at the end of the test.
 func (c *common) runCleanup() {
 	for {

src/testing/testing_test.go

@@ -0,0 +1,109 @@
+// Copyright 2014 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 testing_test
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestTempDirInCleanup(t *testing.T) {
+	var dir string
+
+	t.Run("test", func(t *testing.T) {
+		t.Cleanup(func() {
+			dir = t.TempDir()
+		})
+		_ = t.TempDir()
+	})
+
+	fi, err := os.Stat(dir)
+	if fi != nil {
+		t.Fatalf("Directory %q from user Cleanup still exists", dir)
+	}
+	if !os.IsNotExist(err) {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+}
+
+func TestTempDirInBenchmark(t *testing.T) {
+	testing.Benchmark(func(b *testing.B) {
+		if !b.Run("test", func(b *testing.B) {
+			// Add a loop so that the test won't fail. See issue 38677.
+			for i := 0; i < b.N; i++ {
+				_ = b.TempDir()
+			}
+		}) {
+			t.Fatal("Sub test failure in a benchmark")
+		}
+	})
+}
+
+func TestTempDir(t *testing.T) {
+	testTempDir(t)
+	t.Run("InSubtest", testTempDir)
+	t.Run("test/subtest", testTempDir)
+	t.Run("test\\subtest", testTempDir)
+	t.Run("test:subtest", testTempDir)
+	t.Run("test/..", testTempDir)
+	t.Run("../test", testTempDir)
+	t.Run("test[]", testTempDir)
+	t.Run("test*", testTempDir)
+	t.Run("äöüéè", testTempDir)
+}
+
+func testTempDir(t *testing.T) {
+	dirCh := make(chan string, 1)
+	t.Cleanup(func() {
+		// Verify directory has been removed.
+		select {
+		case dir := <-dirCh:
+			fi, err := os.Stat(dir)
+			if os.IsNotExist(err) {
+				// All good
+				return
+			}
+			if err != nil {
+				t.Fatal(err)
+			}
+			t.Errorf("directory %q still exists: %v, isDir=%v", dir, fi, fi.IsDir())
+		default:
+			if !t.Failed() {
+				t.Fatal("never received dir channel")
+			}
+		}
+	})
+
+	dir := t.TempDir()
+	if dir == "" {
+		t.Fatal("expected dir")
+	}
+	dir2 := t.TempDir()
+	if dir == dir2 {
+		t.Fatal("subsequent calls to TempDir returned the same directory")
+	}
+	if filepath.Dir(dir) != filepath.Dir(dir2) {
+		t.Fatalf("calls to TempDir do not share a parent; got %q, %q", dir, dir2)
+	}
+	dirCh <- dir
+	fi, err := os.Stat(dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !fi.IsDir() {
+		t.Errorf("dir %q is not a dir", dir)
+	}
+
+	glob := filepath.Join(dir, "*.txt")
+	if _, err := filepath.Glob(glob); err != nil {
+		t.Error(err)
+	}
+
+	err = os.Remove(dir)
+	if err != nil {
+		t.Errorf("unexpected files in TempDir")
+	}
+}