Move tagOrDigest to dockerReference

This improves the dockerReference encapsulation, and makes it more clear
that the reference.IsNameOnly case can not happen.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

docker/docker_image_src.go

@@ -59,7 +59,7 @@ func simplifyContentType(contentType string) string {
 }
 
 func (s *dockerImageSource) GetManifest(mimetypes []string) ([]byte, string, error) {
-	reference, err := tagOrDigest(s.ref.ref)
+	reference, err := s.ref.tagOrDigest()
 	if err != nil {
 		return nil, "", err
 	}
@@ -114,7 +114,7 @@ func (s *dockerImageSource) Delete() error {
 	headers := make(map[string][]string)
 	headers["Accept"] = []string{manifest.DockerV2Schema2MIMEType}
 
-	reference, err := tagOrDigest(s.ref.ref)
+	reference, err := s.ref.tagOrDigest()
 	if err != nil {
 		return err
 	}

docker/docker_transport.go

@@ -129,3 +129,15 @@ func (ref dockerReference) NewImageSource(certPath string, tlsVerify bool) (type
 func (ref dockerReference) NewImageDestination(certPath string, tlsVerify bool) (types.ImageDestination, error) {
 	return newImageDestination(ref, certPath, tlsVerify)
 }
+
+// tagOrDigest returns a tag or digest from the reference.
+func (ref dockerReference) tagOrDigest() (string, error) {
+	if ref, ok := ref.ref.(reference.Canonical); ok {
+		return ref.Digest().String(), nil
+	}
+	if ref, ok := ref.ref.(reference.NamedTagged); ok {
+		return ref.Tag(), nil
+	}
+	// This should not happen, NewReference above refuses reference.IsNameOnly values.
+	return "", fmt.Errorf("Internal inconsistency: Reference %s unexpectedly has neither a digest nor a tag", ref.ref.String())
+}

docker/docker_transport_test.go

@@ -177,3 +177,25 @@ func TestReferenceNewImageDestination(t *testing.T) {
 	_, err = ref.NewImageDestination("", true)
 	assert.NoError(t, err)
 }
+
+func TestReferenceTagOrDigest(t *testing.T) {
+	for input, expected := range map[string]string{
+		"//busybox:notlatest":      "notlatest",
+		"//busybox" + sha256digest: "sha256:" + sha256digestHex,
+	} {
+		ref, err := ParseReference(input)
+		require.NoError(t, err, input)
+		dockerRef, ok := ref.(dockerReference)
+		require.True(t, ok, input)
+		tod, err := dockerRef.tagOrDigest()
+		require.NoError(t, err, input)
+		assert.Equal(t, expected, tod, input)
+	}
+
+	// Invalid input
+	ref, err := reference.ParseNamed("busybox")
+	require.NoError(t, err)
+	dockerRef := dockerReference{ref: ref}
+	_, err = dockerRef.tagOrDigest()
+	assert.Error(t, err)
+}

docker/docker_utils.go

@@ -1,18 +0,0 @@
-package docker
-
-import (
-	"fmt"
-
-	"github.com/docker/docker/reference"
-)
-
-// tagOrDigest returns a tag or digest from a reference for which !reference.IsNameOnly.
-func tagOrDigest(ref reference.Named) (string, error) {
-	if ref, ok := ref.(reference.Canonical); ok {
-		return ref.Digest().String(), nil
-	}
-	if ref, ok := ref.(reference.NamedTagged); ok {
-		return ref.Tag(), nil
-	}
-	return "", fmt.Errorf("Internal inconsistency: Reference %s unexpectedly has neither a digest nor a tag", ref.String())
-}