Build from the selected module

internal/tempdir/tempdir.go

@@ -8,32 +8,77 @@ import (
 	"strings"
 )
 
-// Outside uses the system temporary directory and leaves cleanup to its caller.
+// Outside uses system temporary storage and falls back to the repository's
+// parent when TMPDIR resolves inside the worktree. Cleanup belongs to the caller.
 func Outside(repositoryDir, pattern string) (string, error) {
+	repository, err := filepath.Abs(repositoryDir)
+	if err != nil {
+		return "", err
+	}
+	repository, err = filepath.EvalSymlinks(repository)
+	if err != nil {
+		return "", err
+	}
 	directory, err := os.MkdirTemp("", pattern)
 	if err != nil {
 		return "", err
 	}
-	absolute, err := filepath.Abs(directory)
+	created := directory
+	directory, err = filepath.Abs(created)
+	if err != nil {
+		os.RemoveAll(created)
+		return "", err
+	}
+	directory, err = filepath.EvalSymlinks(directory)
 	if err != nil {
 		os.RemoveAll(directory)
 		return "", err
 	}
-	directory = absolute
-	repository, err := filepath.Abs(repositoryDir)
-	if err == nil && !strings.EqualFold(filepath.VolumeName(repository), filepath.VolumeName(directory)) {
+	outside, err := isOutside(repository, directory)
+	if err != nil {
+		os.RemoveAll(directory)
+		return "", err
+	}
+	if outside {
 		return directory, nil
 	}
-	if err == nil {
-		var relative string
-		relative, err = filepath.Rel(repository, directory)
-		if err == nil && (relative == "." || relative != ".." && !strings.HasPrefix(relative, ".."+string(filepath.Separator))) {
-			err = fmt.Errorf("temporary storage %q is inside repository %q; select an external temporary directory", directory, repository)
-		}
+	if err := os.RemoveAll(directory); err != nil {
+		return "", fmt.Errorf("remove temporary storage inside repository %q: %w", repository, err)
 	}
+	directory, err = os.MkdirTemp(filepath.Dir(repository), pattern)
+	if err != nil {
+		return "", fmt.Errorf("create temporary storage outside repository %q: %w", repository, err)
+	}
+	created = directory
+	directory, err = filepath.Abs(created)
+	if err != nil {
+		os.RemoveAll(created)
+		return "", err
+	}
+	directory, err = filepath.EvalSymlinks(directory)
 	if err != nil {
 		os.RemoveAll(directory)
 		return "", err
 	}
+	outside, err = isOutside(repository, directory)
+	if err != nil {
+		os.RemoveAll(directory)
+		return "", err
+	}
+	if !outside {
+		os.RemoveAll(directory)
+		return "", fmt.Errorf("temporary storage %q is inside repository %q", directory, repository)
+	}
 	return directory, nil
 }
+
+func isOutside(repository, directory string) (bool, error) {
+	if !strings.EqualFold(filepath.VolumeName(repository), filepath.VolumeName(directory)) {
+		return true, nil
+	}
+	relative, err := filepath.Rel(repository, directory)
+	if err != nil {
+		return false, err
+	}
+	return relative == ".." || strings.HasPrefix(relative, ".."+string(filepath.Separator)), nil
+}

internal/tempdir/tempdir_test.go

@@ -29,16 +29,28 @@ func TestOutsideHonorsRelativeTemporaryDirectory(t *testing.T) {
 	}
 }
 
-func TestOutsideRejectsAndCleansStorageInsideWorktree(t *testing.T) {
-	repository := t.TempDir()
-	setTemporaryDirectory(t, repository)
-	if directory, err := Outside(repository, "fixture-"); err == nil {
-		os.RemoveAll(directory)
-		t.Fatal("storage created inside worktree")
+func TestOutsideFallsBackWhenTemporaryDirectoryIsInsideWorktree(t *testing.T) {
+	parent := t.TempDir()
+	repository := filepath.Join(parent, "worktree")
+	if err := os.Mkdir(repository, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	localTemporary := filepath.Join(repository, "tmp")
+	if err := os.Mkdir(localTemporary, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	setTemporaryDirectory(t, localTemporary)
+	directory, err := Outside(repository, "fixture-")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(directory)
+	if filepath.Dir(directory) != parent {
+		t.Fatalf("temporary storage=%q want external parent %q", directory, parent)
 	}
 	remaining, err := os.ReadDir(repository)
-	if err != nil || len(remaining) != 0 {
-		t.Fatalf("temporary storage left behind: %v %v", remaining, err)
+	if err != nil || len(remaining) != 1 || remaining[0].Name() != "tmp" {
+		t.Fatalf("temporary storage left behind in worktree: %v %v", remaining, err)
 	}
 }