[ package:dds ] Fix issue where handling a StateError due to a VM

service connection loss could result in a null JSON RPC response.

This would cause package:vm_service to throw a NoSuchMethodError as it
currently assumes it will never receive a null result in a JSON RPC
response.

Related to https://github.com/flutter/flutter/issues/74051.

Change-Id: I86c1c9f7e46e34519f32dfed589c6b31aed39d7f
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/179800
Reviewed-by: Zach Anderson <zra@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>

pkg/dds/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 1.7.2
+- Fixed issue where a null JSON RPC result could be sent if the VM service
+  disconnected with a request in flight (see https://github.com/flutter/flutter/issues/74051).
+
 # 1.7.1
 - Fixed issue where DartDevelopmentServiceException could have a null message.
 

pkg/dds/lib/src/client.dart

@@ -266,12 +266,14 @@ class DartDevelopmentServiceClient {
     // Unless otherwise specified, the request is forwarded to the VM service.
     // NOTE: This must be the last fallback registered.
     _clientPeer.registerFallback((parameters) async {
-      try {
-        return await _vmServicePeer.sendRequest(
-            parameters.method, parameters.value);
-      } on StateError {
-        await dds.shutdown();
-      }
+      // If _vmServicePeer closes in the middle of a request, this will throw
+      // a StateError that will be forwarded to the requesting client.
+      // Listeners in dds_impl.dart will handle shutting down the DDS, so
+      // we don't try and handle the error here.
+      return await _vmServicePeer.sendRequest(
+        parameters.method,
+        parameters.value,
+      );
     });
   }
 

pkg/dds/pubspec.yaml

@@ -3,7 +3,7 @@ description: >-
   A library used to spawn the Dart Developer Service, used to communicate with
   a Dart VM Service instance.
 
-version: 1.7.1
+version: 1.7.2
 
 homepage: https://github.com/dart-lang/sdk/tree/master/pkg/dds
 

pkg/dds/test/handles_client_disconnect_state_error_test.dart

@@ -29,6 +29,9 @@ class StreamCancelDisconnectPeer extends FakePeer {
         completer.completeError(
           StateError('The client closed with pending request "foo".'),
         );
+        doneCompleter.completeError(
+          StateError('The client closed with pending request "foo".'),
+        );
         break;
       default:
         completer.complete(await super.sendRequest(method, args));
@@ -83,8 +86,8 @@ void main() {
     // unexpectedly.
     try {
       await client.sendRequest('foo');
-    } on StateError {
-      // This state error is expected. This test is ensuring that DDS exits
+    } on json_rpc.RpcException {
+      // This RPC exception is expected. This test is ensuring that DDS exits
       // gracefully even if the VM service disappears.
     }