[PRFix using struct instead of pointer for the unmarshal and add tests]

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

copy.go

@@ -70,12 +70,12 @@ func getPlatformFromConfig(ctx context.Context, src content.Storage, desc ocispe
 	}
 	defer rc.Close()
 
-	var platform *ocispec.Platform
-	if err = json.NewDecoder(rc).Decode(&platform); err != nil {
+	var platform ocispec.Platform
+	if err = json.NewDecoder(rc).Decode(&platform); err != nil && err != io.EOF {
 		return nil, err
 	}
 
-	return platform, nil
+	return &platform, nil
 }
 
 // selectPlatform implements platform filter and returns the descriptor of the
@@ -111,9 +111,6 @@ func selectPlatform(ctx context.Context, src content.Storage, root ocispec.Descr
 		if err != nil {
 			return ocispec.Descriptor{}, err
 		}
-		if cfgPlatform == nil {
-			return ocispec.Descriptor{}, fmt.Errorf("%s: missing platform info", descs[0].Digest)
-		}
 
 		if platform.Match(cfgPlatform, p) {
 			return root, nil

copy_test.go

@@ -969,6 +969,80 @@ func TestCopy_WithTargetPlatformOptions(t *testing.T) {
 	if err.Error() != expected {
 		t.Fatalf("Copy() error = %v, wantErr %v", err, expected)
 	}
+
+	// generate test content with null config blob
+	blobs = nil
+	descs = nil
+	appendBlob(ocispec.MediaTypeImageConfig, []byte("null"))     // Blob 0
+	appendBlob(ocispec.MediaTypeImageLayer, []byte("foo2"))      // Blob 1
+	generateManifest(arc_1, os_1, variant_1, descs[0], descs[1]) // Blob 2
+	generateIndex(descs[2])                                      // Blob 3
+
+	ctx = context.Background()
+	for i := range blobs {
+		err := src.Push(ctx, descs[i], bytes.NewReader(blobs[i]))
+		if err != nil {
+			t.Fatalf("failed to push test content to src: %d: %v", i, err)
+		}
+	}
+
+	dst = memory.New()
+	opts = oras.CopyOptions{}
+	targetPlatform = ocispec.Platform{
+		Architecture: arc_1,
+		OS:           os_1,
+	}
+	opts.WithTargetPlatform(&targetPlatform)
+
+	// test copy with platform filter for the manifest with null config blob
+	// should return not found error
+	root = descs[2]
+	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.ErrNotFound) {
+		t.Fatalf("Copy() error = %v, wantErr %v", err, errdef.ErrNotFound)
+	}
+
+	// generate test content with empty config blob
+	blobs = nil
+	descs = nil
+	appendBlob(ocispec.MediaTypeImageConfig, []byte(""))         // Blob 0
+	appendBlob(ocispec.MediaTypeImageLayer, []byte("foo3"))      // Blob 1
+	generateManifest(arc_1, os_1, variant_1, descs[0], descs[1]) // Blob 2
+	generateIndex(descs[2])                                      // Blob 3
+
+	ctx = context.Background()
+	for i := range blobs {
+		err := src.Push(ctx, descs[i], bytes.NewReader(blobs[i]))
+		if err != nil {
+			t.Fatalf("failed to push test content to src: %d: %v", i, err)
+		}
+	}
+
+	dst = memory.New()
+	opts = oras.CopyOptions{}
+	targetPlatform = ocispec.Platform{
+		Architecture: arc_1,
+		OS:           os_1,
+	}
+	opts.WithTargetPlatform(&targetPlatform)
+
+	// test copy with platform filter for the manifest with empty config blob
+	// should return not found error
+	root = descs[2]
+	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.ErrNotFound) {
+		t.Fatalf("Copy() error = %v, wantErr %v", err, errdef.ErrNotFound)
+	}
 }
 
 func TestCopy_RestoreDuplicates(t *testing.T) {