os: implement and test os.MkdirTemp

src/os/file.go

@@ -37,11 +37,6 @@ func Mkdir(path string, perm FileMode) error {
 	return nil
 }
 
-// MkdirTemp is a stub, it will always return an error.
-func MkdirTemp(dir, pattern string) (string, error) {
-	return "", &PathError{"mkdirtemp", dir, ErrNotImplemented}
-}
-
 // Remove removes a file or (empty) directory. If the operation fails, it will
 // return an error of type *PathError.
 func Remove(path string) error {

src/os/tempfile.go

@@ -95,6 +95,46 @@ func prefixAndSuffix(pattern string) (prefix, suffix string, err error) {
 	return prefix, suffix, nil
 }
 
+// MkdirTemp creates a new temporary directory in the directory dir
+// and returns the pathname of the new directory.
+// The new directory's name is generated by adding a random string to the end of pattern.
+// If pattern includes a "*", the random string replaces the last "*" instead.
+// If dir is the empty string, MkdirTemp uses the default directory for temporary files, as returned by TempDir.
+// Multiple programs or goroutines calling MkdirTemp simultaneously will not choose the same directory.
+// It is the caller's responsibility to remove the directory when it is no longer needed.
+func MkdirTemp(dir, pattern string) (string, error) {
+	if dir == "" {
+		dir = TempDir()
+	}
+
+	prefix, suffix, err := prefixAndSuffix(pattern)
+	if err != nil {
+		return "", &PathError{Op: "mkdirtemp", Path: pattern, Err: err}
+	}
+	prefix = joinPath(dir, prefix)
+
+	try := 0
+	for {
+		name := prefix + nextRandom() + suffix
+		err := Mkdir(name, 0700)
+		if err == nil {
+			return name, nil
+		}
+		if IsExist(err) {
+			if try++; try < 10000 {
+				continue
+			}
+			return "", &PathError{Op: "mkdirtemp", Path: dir + string(PathSeparator) + prefix + "*" + suffix, Err: ErrExist}
+		}
+		if IsNotExist(err) {
+			if _, err := Stat(dir); IsNotExist(err) {
+				return "", err
+			}
+		}
+		return "", err
+	}
+}
+
 func joinPath(dir, name string) string {
 	if len(dir) > 0 && IsPathSeparator(dir[len(dir)-1]) {
 		return dir + name

src/os/tempfile_test.go

@@ -8,12 +8,19 @@ import (
 	"errors"
 	. "os"
 	"path/filepath"
+	"regexp"
 	"strings"
 	"testing"
 )
 
 func TestCreateTemp(t *testing.T) {
-	nonexistentDir := filepath.Join("_also_not_exists_", "_not_exists_")
+	dir, err := MkdirTemp("", "TestCreateTempBadDir")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer RemoveAll(dir)
+
+	nonexistentDir := filepath.Join(dir, "_not_exists_")
 	f, err := CreateTemp(nonexistentDir, "foo")
 	if f != nil || err == nil {
 		t.Errorf("CreateTemp(%q, `foo`) = %v, %v", nonexistentDir, f, err)
@@ -43,7 +50,11 @@ func TestCreateTempPattern(t *testing.T) {
 }
 
 func TestCreateTempBadPattern(t *testing.T) {
-	tmpDir := TempDir()
+	tmpDir, err := MkdirTemp("", t.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer RemoveAll(tmpDir)
 
 	const sep = string(PathSeparator)
 	tests := []struct {
@@ -77,3 +88,106 @@ func TestCreateTempBadPattern(t *testing.T) {
 		})
 	}
 }
+
+func TestMkdirTemp(t *testing.T) {
+	name, err := MkdirTemp("/_not_exists_", "foo")
+	if name != "" || err == nil {
+		t.Errorf("MkdirTemp(`/_not_exists_`, `foo`) = %v, %v", name, err)
+	}
+
+	tests := []struct {
+		pattern                string
+		wantPrefix, wantSuffix string
+	}{
+		{"tempfile_test", "tempfile_test", ""},
+		{"tempfile_test*", "tempfile_test", ""},
+		{"tempfile_test*xyz", "tempfile_test", "xyz"},
+	}
+
+	dir := filepath.Clean(TempDir())
+
+	runTestMkdirTemp := func(t *testing.T, pattern, wantRePat string) {
+		name, err := MkdirTemp(dir, pattern)
+		if name == "" || err != nil {
+			t.Fatalf("MkdirTemp(dir, `tempfile_test`) = %v, %v", name, err)
+		}
+		defer Remove(name)
+
+		re := regexp.MustCompile(wantRePat)
+		if !re.MatchString(name) {
+			t.Errorf("MkdirTemp(%q, %q) created bad name\n\t%q\ndid not match pattern\n\t%q", dir, pattern, name, wantRePat)
+		}
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.pattern, func(t *testing.T) {
+			wantRePat := "^" + regexp.QuoteMeta(filepath.Join(dir, tt.wantPrefix)) + "[0-9]+" + regexp.QuoteMeta(tt.wantSuffix) + "$"
+			runTestMkdirTemp(t, tt.pattern, wantRePat)
+		})
+	}
+
+	// Separately testing "*xyz" (which has no prefix). That is when constructing the
+	// pattern to assert on, as in the previous loop, using filepath.Join for an empty
+	// prefix filepath.Join(dir, ""), produces the pattern:
+	//     ^<DIR>[0-9]+xyz$
+	// yet we just want to match
+	//     "^<DIR>/[0-9]+xyz"
+	t.Run("*xyz", func(t *testing.T) {
+		wantRePat := "^" + regexp.QuoteMeta(filepath.Join(dir)) + regexp.QuoteMeta(string(filepath.Separator)) + "[0-9]+xyz$"
+		runTestMkdirTemp(t, "*xyz", wantRePat)
+	})
+}
+
+// test that we return a nice error message if the dir argument to TempDir doesn't
+// exist (or that it's empty and TempDir doesn't exist)
+func TestMkdirTempBadDir(t *testing.T) {
+	dir, err := MkdirTemp("", "MkdirTempBadDir")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer RemoveAll(dir)
+
+	badDir := filepath.Join(dir, "not-exist")
+	_, err = MkdirTemp(badDir, "foo")
+	// TODO: when we drop support for go 1.15, PathError should move to fs
+	if pe, ok := err.(*PathError); !ok || !IsNotExist(err) || pe.Path != badDir {
+		t.Errorf("TempDir error = %#v; want PathError for path %q satisifying IsNotExist", err, badDir)
+	}
+}
+
+func TestMkdirTempBadPattern(t *testing.T) {
+	tmpDir, err := MkdirTemp("", t.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer RemoveAll(tmpDir)
+
+	const sep = string(PathSeparator)
+	tests := []struct {
+		pattern string
+		wantErr bool
+	}{
+		{"ioutil*test", false},
+		{"tempfile_test*foo", false},
+		{"tempfile_test" + sep + "foo", true},
+		{"tempfile_test*" + sep + "foo", true},
+		{"tempfile_test" + sep + "*foo", true},
+		{sep + "tempfile_test" + sep + "*foo", true},
+		{"tempfile_test*foo" + sep, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.pattern, func(t *testing.T) {
+			_, err := MkdirTemp(tmpDir, tt.pattern)
+			if tt.wantErr {
+				if err == nil {
+					t.Errorf("MkdirTemp(..., %#q) succeeded, expected error", tt.pattern)
+				}
+				if !errors.Is(err, ErrPatternHasSeparator) {
+					t.Errorf("MkdirTemp(..., %#q): %v, expected ErrPatternHasSeparator", tt.pattern, err)
+				}
+			} else if err != nil {
+				t.Errorf("MkdirTemp(..., %#q): %v", tt.pattern, err)
+			}
+		})
+	}
+}