Fix grpc-web issue when decoding empty repeated. (#187)

lib/src/client/transport/web_streams.dart

@@ -78,12 +78,11 @@ class _GrpcWebConversionSink extends ChunkedConversionSink<ByteBuffer> {
       final dataLength = _dataHeader.buffer.asByteData().getUint32(0);
       _dataOffset = 0;
       _state = _GrpcWebParseState.Message;
+      _data = new Uint8List(dataLength);
       if (dataLength == 0) {
         // empty message
         _finishMessage();
       }
-
-      _data = new Uint8List(dataLength);
     }
   }
 

lib/src/shared/message.dart

@@ -29,7 +29,7 @@ class GrpcMetadata extends GrpcMessage {
 class GrpcData extends GrpcMessage {
   final List<int> data;
   final bool isCompressed;
-  GrpcData(this.data, {this.isCompressed});
+  GrpcData(this.data, {this.isCompressed}) : assert(data != null);
 
   @override
   String toString() => 'gRPC Data (${data.length} bytes)';

test/grpc_web_decoding_test.dart

@@ -0,0 +1,17 @@
+import 'dart:async';
+import 'dart:typed_data';
+
+import 'package:grpc/src/client/transport/web_streams.dart';
+import 'package:grpc/src/shared/message.dart';
+import 'package:test/test.dart';
+
+main() {
+  test("decoding an empty repeated", () async {
+    final GrpcData data = await GrpcWebDecoder()
+        .bind(Stream.fromIterable([
+          Uint8List.fromList([0, 0, 0, 0, 0]).buffer
+        ]))
+        .first as GrpcData;
+    expect(data.data, []);
+  });
+}