From e135557babfadb6b40fdaabb0cbfa148aa144e23 Mon Sep 17 00:00:00 2001
From: Wei Meng <wemeng@microsoft.com>
Date: Thu, 4 Aug 2022 13:36:49 +0800
Subject: [PATCH] Allow skipping unnamed blobs when pushing to file store
 (#254)

Signed-off-by: Wei Meng <wemeng@microsoft.com>
---
 content/file/errors.go    |  2 ++
 content/file/file.go      | 24 +++++++++++++++---
 content/file/file_test.go | 51 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 73 insertions(+), 4 deletions(-)

diff --git a/content/file/errors.go b/content/file/errors.go
index d140bf8a..36c35d4d 100644
--- a/content/file/errors.go
+++ b/content/file/errors.go
@@ -24,3 +24,5 @@ var (
 	ErrOverwriteDisallowed     = errors.New("overwrite disallowed")
 	ErrStoreClosed             = errors.New("store already closed")
 )
+
+var errSkipUnnamed = errors.New("unnamed descriptor skipped")
diff --git a/content/file/file.go b/content/file/file.go
index 4f5d964a..d72ef64b 100644
--- a/content/file/file.go
+++ b/content/file/file.go
@@ -94,6 +94,14 @@ type Store struct {
 	// ForceCAS can be specified to enforce CAS style dedup.
 	// Default value: false.
 	ForceCAS bool
+	// IgnoreNoName controls if push operations should ignore descriptors
+	// without a name. When specified, corresponding content will be discarded.
+	// Otherwise, content will be saved to a fallback storage.
+	// A typical scenario is pulling an arbitrary artifact masqueraded as OCI
+	// image to file store. This option can be specified to discard unnamed
+	// manifest and config file, while leaving only named layer files.
+	// Default value: false.
+	IgnoreNoName bool
 
 	workingDir   string   // the working directory of the file store
 	closed       int32    // if the store is closed - 0: false, 1: true.
@@ -199,14 +207,18 @@ func (s *Store) Fetch(ctx context.Context, target ocispec.Descriptor) (io.ReadCl
 }
 
 // Push pushes the content, matching the expected descriptor.
-// If name is not specified in the descriptor,
-// the content will be pushed to the fallback storage.
+// If name is not specified in the descriptor, the content will be pushed to
+// the fallback storage by default, or will be discarded when
+// Store.IgnoreNoName is true.
 func (s *Store) Push(ctx context.Context, expected ocispec.Descriptor, content io.Reader) error {
 	if s.isClosedSet() {
 		return ErrStoreClosed
 	}
 
 	if err := s.push(ctx, expected, content); err != nil {
+		if errors.Is(err, errSkipUnnamed) {
+			return nil
+		}
 		return err
 	}
 
@@ -220,11 +232,15 @@ func (s *Store) Push(ctx context.Context, expected ocispec.Descriptor, content i
 }
 
 // push pushes the content, matching the expected descriptor.
-// If name is not specified in the descriptor,
-// the content will be pushed to the fallback storage.
+// If name is not specified in the descriptor, the content will be pushed to
+// the fallback storage by default, or will be discarded when
+// Store.IgnoreNoName is true.
 func (s *Store) push(ctx context.Context, expected ocispec.Descriptor, content io.Reader) error {
 	name := expected.Annotations[ocispec.AnnotationTitle]
 	if name == "" {
+		if s.IgnoreNoName {
+			return errSkipUnnamed
+		}
 		return s.fallbackStorage.Push(ctx, expected, content)
 	}
 
diff --git a/content/file/file_test.go b/content/file/file_test.go
index 5eab0304..b1e98ad6 100644
--- a/content/file/file_test.go
+++ b/content/file/file_test.go
@@ -1670,6 +1670,57 @@ func TestStore_File_Push_DisableOverwrite(t *testing.T) {
 	}
 }
 
+func TestStore_File_Push_IgnoreNoName(t *testing.T) {
+	config := []byte("{}")
+	configDesc := ocispec.Descriptor{
+		MediaType: "config",
+		Digest:    digest.FromBytes(config),
+		Size:      int64(len(config)),
+	}
+	manifest := ocispec.Manifest{
+		MediaType: ocispec.MediaTypeImageManifest,
+		Config:    configDesc,
+		Layers:    []ocispec.Descriptor{},
+	}
+	manifestJSON, err := json.Marshal(manifest)
+	if err != nil {
+		t.Fatal("json.Marshal() error =", err)
+	}
+	manifestDesc := ocispec.Descriptor{
+		MediaType: ocispec.MediaTypeImageManifest,
+		Digest:    digest.FromBytes(manifestJSON),
+		Size:      int64(len(manifestJSON)),
+	}
+	tempDir := t.TempDir()
+	s := New(tempDir)
+	defer s.Close()
+	s.IgnoreNoName = true
+
+	// push an OCI manifest
+	ctx := context.Background()
+	err = s.Push(ctx, manifestDesc, bytes.NewReader(manifestJSON))
+	if err != nil {
+		t.Fatal("Store.Push() error = ", err)
+	}
+
+	// verify the manifest is not saved
+	exists, err := s.Exists(ctx, manifestDesc)
+	if err != nil {
+		t.Fatal("Store.Exists() error =", err)
+	}
+	if exists {
+		t.Errorf("Unnamed manifest is saved in file store")
+	}
+	// verify the manifest is not indexed
+	predecessors, err := s.Predecessors(ctx, configDesc)
+	if err != nil {
+		t.Fatal("Store.Predecessors() error = ", err)
+	}
+	if len(predecessors) != 0 {
+		t.Errorf("Unnamed manifest is indexed in file store")
+	}
+}
+
 func TestStore_File_Push_DisallowPathTraversal(t *testing.T) {
 	content := []byte("hello world")
 	name := "../test.txt"