Always include tag in tarball refs (#893)

pkg/v1/tarball/write.go

@@ -338,11 +338,22 @@ func dedupRefToImage(refToImage map[name.Reference]v1.Image) map[v1.Image][]stri
 
 	for ref, img := range refToImage {
 		if tag, ok := ref.(name.Tag); ok {
-			if tags, ok := imageToTags[img]; ok && tags != nil {
-				imageToTags[img] = append(tags, tag.String())
-			} else {
-				imageToTags[img] = []string{tag.String()}
+			if tags, ok := imageToTags[img]; !ok || tags == nil {
+				imageToTags[img] = []string{}
 			}
+			// Docker cannot load tarballs without an explicit tag:
+			// https://github.com/google/go-containerregistry/issues/890
+			//
+			// We can't use the fully qualified tag.Name() because of rules_docker:
+			// https://github.com/google/go-containerregistry/issues/527
+			//
+			// If the tag is "latest", but tag.String() doesn't end in ":latest",
+			// just append it. Kind of gross, but should work for now.
+			ts := tag.String()
+			if tag.Identifier() == name.DefaultTag && !strings.HasSuffix(ts, ":"+name.DefaultTag) {
+				ts = fmt.Sprintf("%s:%s", ts, name.DefaultTag)
+			}
+			imageToTags[img] = append(imageToTags[img], ts)
 		} else {
 			if _, ok := imageToTags[img]; !ok {
 				imageToTags[img] = nil

pkg/v1/tarball/write_test.go

@@ -378,7 +378,11 @@ func TestWriteSharedLayers(t *testing.T) {
 }
 
 func TestComputeManifest(t *testing.T) {
-	var randomTag, mutatedTag = "gcr.io/foo/bar:latest", "gcr.io/baz/bat:latest"
+	var randomTag, mutatedTag = "ubuntu", "gcr.io/baz/bat:latest"
+
+	// https://github.com/google/go-containerregistry/issues/890
+	randomTagWritten := "ubuntu:latest"
+
 	// Make a random image
 	randImage, err := random.Image(256, 1)
 	if err != nil {
@@ -388,7 +392,7 @@ func TestComputeManifest(t *testing.T) {
 	if err != nil {
 		t.Fatalf("error getting random image config: %v", err)
 	}
-	tag1, err := name.NewTag(randomTag, name.StrictValidation)
+	tag1, err := name.NewTag(randomTag)
 	if err != nil {
 		t.Fatalf("Error creating test tag1.")
 	}
@@ -441,7 +445,7 @@ func TestComputeManifest(t *testing.T) {
 		},
 		{
 			Config:   randConfig.String(),
-			RepoTags: []string{randomTag},
+			RepoTags: []string{randomTagWritten},
 			Layers:   randomLayersFilenames,
 		},
 	}