Speed up workdir by always returning an empty filelist (rather than a nil one). (#557)

Nil indicates that a full snapshot is required. Empty indicates that nothing should be snapshotted.

pkg/commands/workdir.go

@@ -34,6 +34,9 @@ type WorkdirCommand struct {
 	snapshotFiles []string
 }
 
+// For testing
+var mkdir = os.MkdirAll
+
 func (w *WorkdirCommand) ExecuteCommand(config *v1.Config, buildArgs *dockerfile.BuildArgs) error {
 	logrus.Info("cmd: workdir")
 	workdirPath := w.cmd.Path
@@ -50,10 +53,11 @@ func (w *WorkdirCommand) ExecuteCommand(config *v1.Config, buildArgs *dockerfile
 	logrus.Infof("Changed working directory to %s", config.WorkingDir)
 
 	// Only create and snapshot the dir if it didn't exist already
+	w.snapshotFiles = []string{}
 	if _, err := os.Stat(config.WorkingDir); os.IsNotExist(err) {
 		logrus.Infof("Creating directory %s", config.WorkingDir)
-		w.snapshotFiles = []string{config.WorkingDir}
+		w.snapshotFiles = append(w.snapshotFiles, config.WorkingDir)
-		return os.MkdirAll(config.WorkingDir, 0755)
+		return mkdir(config.WorkingDir, 0755)
 	}
 	return nil
 }

pkg/commands/workdir_test.go

@@ -16,6 +16,7 @@ limitations under the License.
 package commands
 
 import (
+	"os"
 	"testing"
 
 	"github.com/GoogleContainerTools/kaniko/pkg/dockerfile"
@@ -32,39 +33,64 @@ import (
 var workdirTests = []struct {
 	path          string
 	expectedPath  string
+	snapshotFiles []string
 }{
 	{
 		path:          "/a",
 		expectedPath:  "/a",
+		snapshotFiles: []string{"/a"},
 	},
 	{
 		path:          "b",
 		expectedPath:  "/a/b",
+		snapshotFiles: []string{"/a/b"},
 	},
 	{
 		path:          "c",
 		expectedPath:  "/a/b/c",
+		snapshotFiles: []string{"/a/b/c"},
 	},
 	{
 		path:          "/d",
 		expectedPath:  "/d",
+		snapshotFiles: []string{"/d"},
 	},
 	{
 		path:          "$path",
 		expectedPath:  "/d/usr",
+		snapshotFiles: []string{"/d/usr"},
 	},
 	{
 		path:          "$home",
 		expectedPath:  "/root",
+		snapshotFiles: []string{},
 	},
 	{
-		path:         "$path/$home",
+		path:          "/foo/$path/$home",
-		expectedPath: "/root/usr/root",
+		expectedPath:  "/foo/usr/root",
+		snapshotFiles: []string{"/foo/usr/root"},
+	},
+	{
+		path:          "/tmp",
+		expectedPath:  "/tmp",
+		snapshotFiles: []string{},
 	},
 }
 
+// For testing
+func mockDir(p string, fi os.FileMode) error {
+	return nil
+}
 func TestWorkdirCommand(t *testing.T) {
 
+	// Mock out mkdir for testing.
+	oldMkdir := mkdir
+	mkdir = mockDir
+
+	defer func() {
+		mkdir = oldMkdir
+	}()
+
 	cfg := &v1.Config{
 		WorkingDir: "/",
 		Env: []string{
@@ -78,10 +104,11 @@ func TestWorkdirCommand(t *testing.T) {
 			cmd: &instructions.WorkdirCommand{
 				Path: test.path,
 			},
-			snapshotFiles: []string{},
+			snapshotFiles: nil,
 		}
 		buildArgs := dockerfile.NewBuildArgs([]string{})
 		cmd.ExecuteCommand(cfg, buildArgs)
 		testutil.CheckErrorAndDeepEqual(t, false, nil, test.expectedPath, cfg.WorkingDir)
+		testutil.CheckErrorAndDeepEqual(t, false, nil, test.snapshotFiles, cmd.snapshotFiles)
 	}
 }