Merge pull request #1797 from crazy-max/fix-image-create

util/imagetools/create.go

@@ -122,24 +122,29 @@ func (r *Resolver) Combine(ctx context.Context, srcs []*Source) ([]byte, ocispec
 		}
 	}
 
-	mt := images.MediaTypeDockerSchema2ManifestList //ocispec.MediaTypeImageIndex
+	dockerMfsts := 0
-	idx := struct {
+	for _, desc := range newDescs {
-		// MediaType is reserved in the OCI spec but
+		if strings.HasPrefix(desc.MediaType, "application/vnd.docker.") {
-		// excluded from go types.
+			dockerMfsts++
-		MediaType string `json:"mediaType,omitempty"`
+		}
-
-		ocispec.Index
-	}{
-		MediaType: mt,
-		Index: ocispec.Index{
-			Versioned: specs.Versioned{
-				SchemaVersion: 2,
-			},
-			Manifests: newDescs,
-		},
 	}
 
-	idxBytes, err := json.MarshalIndent(idx, "", "  ")
+	var mt string
+	if dockerMfsts == len(newDescs) {
+		// all manifests are Docker types, use Docker manifest list
+		mt = images.MediaTypeDockerSchema2ManifestList
+	} else {
+		// otherwise, use OCI index
+		mt = ocispec.MediaTypeImageIndex
+	}
+
+	idxBytes, err := json.MarshalIndent(ocispec.Index{
+		MediaType: mt,
+		Versioned: specs.Versioned{
+			SchemaVersion: 2,
+		},
+		Manifests: newDescs,
+	}, "", "  ")
 	if err != nil {
 		return nil, ocispec.Descriptor{}, errors.Wrap(err, "failed to marshal index")
 	}