Decode gRPC error message (#326)

lib/src/client/call.dart

@@ -242,7 +242,9 @@ class ClientCall<Q, R> implements Response {
       // TODO(jakobr): Parse more!
       if (metadata.containsKey('grpc-status')) {
         final status = int.parse(metadata['grpc-status']);
-        final message = metadata['grpc-message'];
+        final message = metadata['grpc-message'] == null
+            ? null
+            : Uri.decodeFull(metadata['grpc-message']);
         if (status != 0) {
           _responseError(GrpcError.custom(status, message));
         }
@@ -283,7 +285,9 @@ class ClientCall<Q, R> implements Response {
       // If status code is missing, we must treat it as '0'. As in 'success'.
       final statusCode = status != null ? int.parse(status) : 0;
       if (statusCode != 0) {
-        final message = _headerMetadata['grpc-message'];
+        final message = _headerMetadata['grpc-message'] == null
+            ? null
+            : Uri.decodeFull(_headerMetadata['grpc-message']);
         _responseError(GrpcError.custom(statusCode, message));
       }
     }

test/client_tests/client_test.dart

@@ -257,6 +257,27 @@ void main() {
     );
   });
 
+  test('Call throws decoded message', () async {
+    const customStatusCode = 17;
+    const customStatusMessage = 'エラー';
+    const encodedCustomStatusMessage = '%E3%82%A8%E3%83%A9%E3%83%BC';
+
+    void handleRequest(_) {
+      harness.toClient.add(HeadersStreamMessage([
+        Header.ascii('grpc-status', '$customStatusCode'),
+        Header.ascii('grpc-message', encodedCustomStatusMessage)
+      ], endStream: true));
+      harness.toClient.close();
+    }
+
+    await harness.runFailureTest(
+      clientCall: harness.client.unary(dummyValue),
+      expectedException:
+          GrpcError.custom(customStatusCode, customStatusMessage),
+      serverHandlers: [handleRequest],
+    );
+  });
+
   test('Call throws on response stream errors', () async {
     void handleRequest(_) {
       harness.toClient.addError('Test error');