Add await to callsites of BasicMessageChannel.send by victorsanni · Pull Request #182868 · flutter/flutter

victorsanni · 2026-02-24T22:51:33Z

Impl:

  /// Sends the specified [message] to the platform plugins on this channel.
  ///
  /// Returns a [Future] which completes to the received response, which may
  /// be null.
  Future<T?> send(T message) async {
    return codec.decodeMessage(await binaryMessenger.send(name, codec.encodeMessage(message)));
  }

Part of #181513

gemini-code-assist

Code Review

This pull request adds await to callsites of BasicMessageChannel.send, which is now an async method. The changes are generally correct and necessary. However, I've found a couple of issues in the benchmark file dev/benchmarks/platform_channels_benchmarks/lib/main.dart. One change introduces a performance regression by serializing parallel operations, and another uses an async/await anti-pattern. I've provided suggestions to fix these issues.

gemini-code-assist · 2026-02-24T22:56:04Z

dev/benchmarks/platform_channels_benchmarks/lib/main.dart

+    await basicStandard.send(payload).then((Object? result) {
      _runBasicStandardParallelRecurse(basicStandard, counter, count, completer, payload);
    });


Adding await inside this loop makes it sequential, which defeats the purpose of the _runBasicStandardParallel benchmark. Each iteration now waits for the send operation to complete before starting the next, removing the parallelism.

To restore the parallel behavior, the await should be removed.

basicStandard.send(payload).then((Object? result) { _runBasicStandardParallelRecurse(basicStandard, counter, count, completer, payload); });

Use await Future.forEach() or Future.wait instead.

gemini-code-assist · 2026-02-24T22:56:04Z

dev/benchmarks/platform_channels_benchmarks/lib/main.dart

+    await basicStandard.send(payload).then((Object? result) {
      _runBasicStandardParallelRecurse(basicStandard, counter, count, completer, payload);
    });


Using await with .then() is an anti-pattern in modern Dart as it can be expressed more clearly using async/await. This also avoids creating a Future<Future<void>> which is likely not intended.

await basicStandard.send(payload); _runBasicStandardParallelRecurse(basicStandard, counter, count, completer, payload);

examples/flutter_view/lib/main.dart

dkwingsmt · 2026-02-24T23:09:43Z

packages/flutter/lib/src/widgets/navigator.dart

This future should have a .catch that reports error.

Is the current impl satisfactory?

dkwingsmt

Generally ok.

dkwingsmt · 2026-02-25T06:08:46Z

dev/benchmarks/platform_channels_benchmarks/lib/main.dart

-    basicStandard.send(payload).then((Object? result) {
-      _runBasicStandardParallelRecurse(basicStandard, counter, count, completer, payload);
-    });
+    await Future.wait([


Future.wait is meant to run tasks in parallel and wait for the completion of all of them.

You should replace the entire for loop with something like (psuedocode):

await Future.wait(List.generate(parallel, (_) => () async { await basicStandard.send(payload); await _runBasicStandardParallelRecurse(basicStandard, counter, count, completer, payload); }));

packages/flutter/lib/src/semantics/semantics.dart

victorsanni · 2026-02-25T19:28:02Z

dev/benchmarks/platform_channels_benchmarks/lib/main.dart

+  await Future.wait(
+    Iterable.generate(parallel, (_) async {
+      await basicStandard.send(payload);
+      // ignore: unawaited_futures


Ignoring because recursive method is intended to run in parallel

Are you sure we can't have await here? I think this still runs in parallel even if you use await, since Iterable.generate runs everything at the same time. In other words, each (_) async { ... } runs in parallel.

dkwingsmt · 2026-02-27T18:41:36Z

dev/benchmarks/platform_channels_benchmarks/lib/main.dart

-      _runBasicStandardParallelRecurse(basicStandard, counter, count, completer, payload);
-    });
+    await basicStandard.send(payload);
+    _runBasicStandardParallelRecurse(basicStandard, counter, count, completer, payload);


await (or return)

packages/flutter/lib/src/semantics/semantics.dart

dkwingsmt · 2026-02-27T21:35:21Z

dev/benchmarks/platform_channels_benchmarks/lib/main.dart

@@ -68,11 +67,12 @@ Future<double> _runBasicStandardParallel(
  final completer = Completer<int>();
  final counter = _Counter();
  watch.start();
-  for (var i = 0; i < parallel; ++i) {
-    basicStandard.send(payload).then((Object? result) {
-      _runBasicStandardParallelRecurse(basicStandard, counter, count, completer, payload);
-    });
-  }
+  await Future.wait(
+    Iterable.generate(parallel, (_) async {
+      await basicStandard.send(payload);
+      await _runBasicStandardParallelRecurse(basicStandard, counter, count, completer, payload);
+    }),
+  );


I'm sorry but I just realized that we might have been doing something wrong. _runBasicStandardParallelRecurse is using its completer parameter as the async control, and shouldn't need additional Future return value.

(I suspect that this entire function is basically reinventing Future.wait from scratch.)

In short, I think the original implementation is probably completely correct and we shouldn't change it at all. It doesn't have anything that violate the lint either, right? All futures either has .then or is awaited.

…/flutter#182868)

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Impl: ```dart /// Sends the specified [message] to the platform plugins on this channel. /// /// Returns a [Future] which completes to the received response, which may /// be null. Future<T?> send(T message) async { return codec.decodeMessage(await binaryMessenger.send(name, codec.encodeMessage(message))); } ``` Part of flutter#181513

Add await to callsites of BasicMessageChannel.send

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victorsanni requested a review from dkwingsmt February 24, 2026 22:51

github-actions bot added framework flutter/packages/flutter repository. See also f: labels. a: accessibility Accessibility, e.g. VoiceOver or TalkBack. (aka a11y) d: examples Sample code and demos f: routes Navigator, Router, and related APIs. labels Feb 24, 2026

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Revert platform_channel_benchmarks/lib/main.dart

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victorsanni commented Feb 24, 2026 •

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