Merge pull request moby#4051 from jake-ciolek/with-allow-not-found-bug

file: Fix incorrect handling of non-existent files in llbsolver's rmPath

Author: tonistiigi

solver/llbsolver/file/backend.go

@@ -161,14 +161,15 @@ func rmPath(root, src string, allowNotFound bool) error {
 	}
 	p := filepath.Join(dir, base)
 
-	if err := os.RemoveAll(p); err != nil {
-		if errors.Is(err, os.ErrNotExist) && allowNotFound {
-			return nil
+	if !allowNotFound {
+		_, err := os.Stat(p)
+
+		if errors.Is(err, os.ErrNotExist) {
+			return err
 		}
-		return err
 	}
 
-	return nil
+	return os.RemoveAll(p)
 }
 
 func docopy(ctx context.Context, src, dest string, action pb.FileActionCopy, u *copy.User, idmap *idtools.IdentityMapping) error {

solver/llbsolver/file/backend_test.go

@@ -0,0 +1,36 @@
+package file
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestRmPathNonExistentFileAllowNotFoundFalse(t *testing.T) {
+	root := t.TempDir()
+	err := rmPath(root, "doesnt_exist", false)
+	require.Error(t, err)
+	require.True(t, os.IsNotExist(err))
+}
+
+func TestRmPathNonExistentFileAllowNotFoundTrue(t *testing.T) {
+	root := t.TempDir()
+	require.NoError(t, rmPath(root, "doesnt_exist", true))
+}
+
+func TestRmPathFileExists(t *testing.T) {
+	root := t.TempDir()
+
+	src := filepath.Join(root, "exists")
+	file, err := os.Create(src)
+	require.NoError(t, err)
+	file.Close()
+
+	require.NoError(t, rmPath(root, "exists", false))
+
+	_, err = os.Stat(src)
+
+	require.True(t, os.IsNotExist(err))
+}