Beacon API: fix get blob returns 500 instead of empty (#13297)

* fix blob api, should return empty if no indicies were found

* fixing small bug with slice

beacon-chain/rpc/eth/blob/handlers_test.go

@@ -37,8 +37,7 @@ func TestBlobs(t *testing.T) {
 	db := testDB.SetupDB(t)
 	denebBlock, blobs := util.GenerateTestDenebBlockWithSidecar(t, [32]byte{}, 123, 4)
 	require.NoError(t, db.SaveBlock(context.Background(), denebBlock))
-	_, bs, err := filesystem.NewEphemeralBlobStorageWithFs(t)
-	require.NoError(t, err)
+	bs := filesystem.NewEphemeralBlobStorage(t)
 	testSidecars, err := verification.BlobSidecarSliceNoop(blobs)
 	require.NoError(t, err)
 	for i := range testSidecars {
@@ -218,6 +217,26 @@ func TestBlobs(t *testing.T) {
 		assert.Equal(t, hexutil.Encode(blobs[2].KzgCommitment), sidecar.KzgCommitment)
 		assert.Equal(t, hexutil.Encode(blobs[2].KzgProof), sidecar.KzgProof)
 	})
+	t.Run("no blobs returns an empty array", func(t *testing.T) {
+		u := "http://foo.example/123"
+		request := httptest.NewRequest("GET", u, nil)
+		writer := httptest.NewRecorder()
+		writer.Body = &bytes.Buffer{}
+		blocker := &lookup.BeaconDbBlocker{
+			ChainInfoFetcher: &mockChain.ChainService{FinalizedCheckPoint: &eth.Checkpoint{Root: blockRoot[:]}},
+			BeaconDB:         db,
+			BlobStorage:      filesystem.NewEphemeralBlobStorage(t), // new ephemeral storage
+		}
+		s := &Server{
+			Blocker: blocker,
+		}
+
+		s.Blobs(writer, request)
+		assert.Equal(t, http.StatusOK, writer.Code)
+		resp := &SidecarsResponse{}
+		require.NoError(t, json.Unmarshal(writer.Body.Bytes(), resp))
+		require.Equal(t, len(resp.Data), 0)
+	})
 	t.Run("slot before Deneb fork", func(t *testing.T) {
 		u := "http://foo.example/31"
 		request := httptest.NewRequest("GET", u, nil)

beacon-chain/rpc/lookup/blocker.go

@@ -139,7 +139,6 @@ func (p *BeaconDbBlocker) Block(ctx context.Context, id []byte) (interfaces.Read
 //   - <hex encoded block root with '0x' prefix>
 //   - <block root>
 func (p *BeaconDbBlocker) Blobs(ctx context.Context, id string, indices []uint64) ([]*blocks.VerifiedROBlob, *core.RpcError) {
-	var blobs []*blocks.VerifiedROBlob
 	var root []byte
 	switch id {
 	case "genesis":
@@ -219,17 +218,14 @@ func (p *BeaconDbBlocker) Blobs(ctx context.Context, id string, indices []uint64
 			}
 		}
 	}
-
-	if len(indices) == 0 {
-		return nil, &core.RpcError{Err: errors.New("no blobs found"), Reason: core.Internal}
-	}
-
-	for _, index := range indices {
+	// returns empty slice if there are no indices
+	blobs := make([]*blocks.VerifiedROBlob, len(indices))
+	for i, index := range indices {
 		vblob, err := p.BlobStorage.Get(bytesutil.ToBytes32(root), index)
 		if err != nil {
 			return nil, &core.RpcError{Err: errors.Wrapf(err, "could not retrieve blob for block root %#x at index %d", root, index), Reason: core.Internal}
 		}
-		blobs = append(blobs, &vblob)
+		blobs[i] = &vblob
 	}
 	return blobs, nil
 }

beacon-chain/rpc/lookup/blocker_test.go

@@ -267,4 +267,14 @@ func TestGetBlob(t *testing.T) {
 		assert.DeepEqual(t, blobs[2].KzgCommitment, sidecar.KzgCommitment)
 		assert.DeepEqual(t, blobs[2].KzgProof, sidecar.KzgProof)
 	})
+	t.Run("no blobs returns an empty array", func(t *testing.T) {
+		blocker := &BeaconDbBlocker{
+			ChainInfoFetcher: &mockChain.ChainService{FinalizedCheckPoint: &ethpbalpha.Checkpoint{Root: blockRoot[:]}},
+			BeaconDB:         db,
+			BlobStorage:      filesystem.NewEphemeralBlobStorage(t),
+		}
+		verifiedBlobs, rpcErr := blocker.Blobs(ctx, "123", nil)
+		assert.Equal(t, rpcErr == nil, true)
+		require.Equal(t, 0, len(verifiedBlobs))
+	})
 }