[PRFix add Resolve and support manifest platform selection]

Signed-off-by: Zoey Li <zoeyli@microsoft.com>

content.go

@@ -18,6 +18,7 @@ package oras
 import (
 	"context"
 
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"oras.land/oras-go/v2/registry"
 )
 
@@ -42,3 +43,27 @@ func Tag(ctx context.Context, target Target, src, dst string) error {
 	}
 	return target.Tag(ctx, desc, dst)
 }
+
+// ResolveOptions contains parameters for oras.Resolve.
+type ResolveOptions struct {
+	// MatchPlaform is the target platform.
+	// Will do the platform selection if specified.
+	MatchPlatform *ocispec.Platform
+}
+
+// Resolve returns the resolved descriptor.
+func Resolve(ctx context.Context, target Target, ref string, opts ResolveOptions) (ocispec.Descriptor, error) {
+	desc, err := target.Resolve(ctx, ref)
+	if err != nil {
+		return ocispec.Descriptor{}, err
+	}
+
+	if opts.MatchPlatform != nil {
+		desc, err = selectPlatform(ctx, target, desc, opts.MatchPlatform)
+		if err != nil {
+			return ocispec.Descriptor{}, err
+		}
+	}
+
+	return desc, nil
+}

copy.go

@@ -17,6 +17,7 @@ package oras
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -57,24 +58,52 @@ type CopyOptions struct {
 }
 
 // selectPlatform implements platform filter and returns the descriptor of
-// the first matched manifest from the manifest list / image index.
+// the first matched manifest if the root is a manifest list / image index.
+// If the root is a manifest, then return the root descriptor if platform
+// matches.
 func selectPlatform(ctx context.Context, src content.Storage, root ocispec.Descriptor, p *ocispec.Platform) (ocispec.Descriptor, error) {
-	if root.MediaType != docker.MediaTypeManifestList && root.MediaType != ocispec.MediaTypeImageIndex {
-		return ocispec.Descriptor{}, fmt.Errorf("%s: %s: %w", root.Digest, root.MediaType, errdef.ErrUnsupported)
-	}
+	switch root.MediaType {
+	case docker.MediaTypeManifestList, ocispec.MediaTypeImageIndex:
+		manifests, err := content.Successors(ctx, src, root)
+		if err != nil {
+			return ocispec.Descriptor{}, err
+		}
 
-	manifests, err := content.Successors(ctx, src, root)
-	if err != nil {
-		return ocispec.Descriptor{}, err
-	}
+		// platform filter
+		for _, m := range manifests {
+			if platform.Match(m.Platform, p) {
+				return m, nil
+			}
+		}
+		return ocispec.Descriptor{}, errdef.ErrNotFound
+	case docker.MediaTypeManifest, ocispec.MediaTypeImageManifest:
+		descs, err := content.Successors(ctx, src, root)
+		if err != nil {
+			return ocispec.Descriptor{}, err
+		}
 
-	// platform filter
-	for _, m := range manifests {
-		if platform.MatchPlatform(m.Platform, p) {
-			return m, nil
+		for _, desc := range descs {
+			if desc.MediaType == docker.MediaTypeImage || desc.MediaType == ocispec.MediaTypeImageConfig {
+				rc, err := src.Fetch(ctx, desc)
+				if err != nil {
+					return ocispec.Descriptor{}, err
+				}
+				var currPlatform ocispec.Platform
+				err = json.NewDecoder(rc).Decode(&currPlatform)
+				if err != nil {
+					return ocispec.Descriptor{}, err
+				}
+				defer rc.Close()
+
+				if platform.Match(&currPlatform, p) {
+					return root, nil
+				}
+			}
 		}
+		return ocispec.Descriptor{}, errdef.ErrNotFound
+	default:
+		return ocispec.Descriptor{}, fmt.Errorf("%s: %s: %w", root.Digest, root.MediaType, errdef.ErrUnsupported)
 	}
-	return ocispec.Descriptor{}, errdef.ErrNotFound
 }
 
 // WithPlatformFilter adds the check on the platform attributes.

copy_test.go

@@ -707,7 +707,12 @@ func TestCopy_WithPlatformFilterOptions(t *testing.T) {
 		appendBlob(ocispec.MediaTypeImageIndex, indexJSON)
 	}
 
-	appendBlob(ocispec.MediaTypeImageConfig, []byte("config"))                 // Blob 0
+	appendBlob(ocispec.MediaTypeImageConfig, []byte(`{"mediaType":"application/vnd.oci.image.config.v1+json",
+"created":"2022-07-29T08:13:55Z",
+"author":"test author",
+"architecture":"test-arc-1",
+"os":"test-os-1",
+"variant":"test-variant"}`)) // Blob 0
 	appendBlob(ocispec.MediaTypeImageLayer, []byte("foo"))                     // Blob 1
 	appendBlob(ocispec.MediaTypeImageLayer, []byte("bar"))                     // Blob 2
 	generateManifest("test-arc-1", "test-os-1", "v1", descs[0], descs[1:3]...) // Blob 3
@@ -732,7 +737,7 @@ func TestCopy_WithPlatformFilterOptions(t *testing.T) {
 		t.Fatal("fail to tag root node", err)
 	}
 
-	// test copy with platform filter
+	// test copy with platform filter for the image index
 	dst := memory.New()
 	opts := oras.CopyOptions{}
 	targetPlatform := ocispec.Platform{
@@ -769,8 +774,9 @@ func TestCopy_WithPlatformFilterOptions(t *testing.T) {
 		t.Errorf("dst.Resolve() = %v, want %v", gotDesc, wantDesc)
 	}
 
-	// test copy with platform filter, if the multiple manifests match the required platform,
-	// return the first matching entry
+	// test copy with platform filter for the image index, and multiple
+	// manifests match the required platform. Should return the first
+	// matching entry.
 	dst = memory.New()
 	targetPlatform = ocispec.Platform{
 		Architecture: "test-arc-1",
@@ -807,8 +813,9 @@ func TestCopy_WithPlatformFilterOptions(t *testing.T) {
 		t.Errorf("dst.Resolve() = %v, want %v", gotDesc, wantDesc)
 	}
 
-	// test copy with platform filter and existing MapRoot func, but no matching node can be found
-	// should return not found error
+	// test copy with platform filter and existing MapRoot func for the
+	// image index, but there is no matching node. Should return not found
+	// error.
 	dst = memory.New()
 	opts = oras.CopyOptions{
 		MapRoot: func(ctx context.Context, src content.Storage, root ocispec.Descriptor) (ocispec.Descriptor, error) {
@@ -830,8 +837,7 @@ func TestCopy_WithPlatformFilterOptions(t *testing.T) {
 		t.Fatalf("Copy() error = %v, wantErr %v", err, errdef.ErrNotFound)
 	}
 
-	// test copy with platform filter, but the node's media type is not supported
-	// should return unsupported error
+	// test copy with platform filter for the manifest
 	dst = memory.New()
 	opts = oras.CopyOptions{}
 	targetPlatform = ocispec.Platform{
@@ -846,6 +852,67 @@ func TestCopy_WithPlatformFilterOptions(t *testing.T) {
 		t.Fatal("fail to tag root node", err)
 	}
 
+	wantDesc = descs[7]
+	gotDesc, err = oras.Copy(ctx, src, ref, dst, "", opts)
+	if err != nil {
+		t.Fatalf("Copy() error = %v, wantErr %v", err, false)
+	}
+	if !reflect.DeepEqual(gotDesc, wantDesc) {
+		t.Errorf("Copy() = %v, want %v", gotDesc, wantDesc)
+	}
+
+	// verify contents
+	for i, desc := range append([]ocispec.Descriptor{descs[0]}, descs[6]) {
+		exists, err := dst.Exists(ctx, desc)
+		if err != nil {
+			t.Fatalf("dst.Exists(%d) error = %v", i, err)
+		}
+		if !exists {
+			t.Errorf("dst.Exists(%d) = %v, want %v", i, exists, true)
+		}
+	}
+
+	// verify tag
+	gotDesc, err = dst.Resolve(ctx, ref)
+	if err != nil {
+		t.Fatal("dst.Resolve() error =", err)
+	}
+	if !reflect.DeepEqual(gotDesc, wantDesc) {
+		t.Errorf("dst.Resolve() = %v, want %v", gotDesc, wantDesc)
+	}
+
+	// test copy with platform filter for the manifest, but there is no
+	// matching node. Should return not found error.
+	dst = memory.New()
+	opts = oras.CopyOptions{}
+	targetPlatform = ocispec.Platform{
+		Architecture: "test-arc-1",
+		OS:           "test-os-1",
+		Variant:      "wrong-variant",
+	}
+	opts.WithPlatformFilter(&targetPlatform)
+
+	_, err = oras.Copy(ctx, src, ref, dst, "", opts)
+	if !errors.Is(err, errdef.ErrNotFound) {
+		t.Fatalf("Copy() error = %v, wantErr %v", err, errdef.ErrNotFound)
+	}
+
+	// test copy with platform filter, but the node's media type is not
+	// supported. Should return unsupported error
+	dst = memory.New()
+	opts = oras.CopyOptions{}
+	targetPlatform = ocispec.Platform{
+		Architecture: "test-arc-1",
+		OS:           "test-os-1",
+	}
+	opts.WithPlatformFilter(&targetPlatform)
+
+	root = descs[1]
+	err = src.Tag(ctx, root, ref)
+	if err != nil {
+		t.Fatal("fail to tag root node", err)
+	}
+
 	_, err = oras.Copy(ctx, src, ref, dst, "", opts)
 	if !errors.Is(err, errdef.ErrUnsupported) {
 		t.Fatalf("Copy() error = %v, wantErr %v", err, errdef.ErrUnsupported)

internal/docker/mediatype.go

@@ -17,6 +17,7 @@ package docker
 
 // docker media types
 const (
+	MediaTypeImage        = "application/vnd.docker.container.image.v1+json"
 	MediaTypeManifestList = "application/vnd.docker.distribution.manifest.list.v2+json"
 	MediaTypeManifest     = "application/vnd.docker.distribution.manifest.v2+json"
 )

internal/platform/platform.go

@@ -19,15 +19,15 @@ import (
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
-// MatchPlatform checks whether the current platform matches the target platform.
-// MatchPlatform will return true if all of the following conditions are met.
+// Match checks whether the current platform matches the target platform.
+// Match will return true if all of the following conditions are met.
 // - Architecture and OS exactly match.
 // - Variant and OSVersion exactly match if target platform provided.
-// - OSFeatures of the target platform are the subsets of the OSFeatures array
-//   of the current platform.
-// Note: Variant, OSVersion and OSFeatures are optional fields, will skip the
-// comparison if the target platform does not provide specfic value.
-func MatchPlatform(got *ocispec.Platform, want *ocispec.Platform) bool {
+// - OSFeatures of the target platform are the subsets of the OSFeatures
+//   array of the current platform.
+// Note: Variant, OSVersion and OSFeatures are optional fields, will skip
+// the comparison if the target platform does not provide specfic value.
+func Match(got *ocispec.Platform, want *ocispec.Platform) bool {
 	if got.Architecture != want.Architecture || got.OS != want.OS {
 		return false
 	}

internal/platform/platform_test.go

@@ -22,7 +22,7 @@ import (
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
-func TestMatchPlatform(t *testing.T) {
+func TestMatch(t *testing.T) {
 	tests := []struct {
 		curr   ocispec.Platform
 		target ocispec.Platform
@@ -94,7 +94,7 @@ func TestMatchPlatform(t *testing.T) {
 		targetPlatforJSON, _ := json.Marshal(tt.target)
 		name := string(currPlatforJSON) + string(targetPlatforJSON)
 		t.Run(name, func(t *testing.T) {
-			if got := MatchPlatform(&tt.curr, &tt.target); got != tt.want {
+			if got := Match(&tt.curr, &tt.target); got != tt.want {
 				t.Errorf("MatchPlatform() = %v, want %v", got, tt.want)
 			}
 		})