feat: support deletion for memory resolver (#607)

Part 2/4 of #454 

Based on draft PR #582

---------

Signed-off-by: Xiaoxuan Wang <[email protected]>
Co-authored-by: Terry Howe <[email protected]>

Author: wangxiaoxuan273

internal/resolver/memory.go

@@ -48,6 +48,11 @@ func (m *Memory) Tag(_ context.Context, desc ocispec.Descriptor, reference strin
 	return nil
 }
 
+// Untag removes a reference from index map.
+func (m *Memory) Untag(reference string) {
+	m.index.Delete(reference)
+}
+
 // Map dumps the memory into a built-in map structure.
 // Like other operations, calling Map() is go-routine safe. However, it does not
 // necessarily correspond to any consistent snapshot of the storage contents.

internal/resolver/memory_test.go

@@ -54,6 +54,15 @@ func TestMemorySuccess(t *testing.T) {
 	if got := len(s.Map()); got != 1 {
 		t.Errorf("Memory.Map() = %v, want %v", got, 1)
 	}
+
+	s.Untag(ref)
+	_, err = s.Resolve(ctx, ref)
+	if !errors.Is(err, errdef.ErrNotFound) {
+		t.Errorf("Memory.Resolve() error = %v, want %v", err, errdef.ErrNotFound)
+	}
+	if got := len(s.Map()); got != 0 {
+		t.Errorf("Memory.Map() = %v, want %v", got, 0)
+	}
 }
 
 func TestMemoryNotFound(t *testing.T) {