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Merged
auto-submit merged 1 commit into from
Sep 12, 2025
Merged

[CP-stable][shell] Fix engineId not being set after hot restart #175255

auto-submit merged 1 commit into from
Sep 12, 2025

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@flutteractionsbot flutteractionsbot commented Sep 12, 2025 •
edited by HosseinYousefi
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This pull request is created by automatic cherry pick workflow
Please fill in the form below, and a flutter domain expert will evaluate this cherry pick request.

Issue Link:

What is the link to the issue this cherry-pick is addressing?

#173474

Changelog Description:

Explain this cherry pick in one line that is accessible to most Flutter developers. See best practices for examples

PlatformDispatchers.instance.engineId returns null after hot restart

Impact Description:

What is the impact (ex. visual jank on Samsung phones, app crash, cannot ship an iOS app)? Does it impact development (ex. flutter doctor crashes when Android Studio is installed), or the shipping production app (the app crashes on launch)

It affects anyone who uses engineId while in development (since it happens after hot-restart).

Workaround:

Is there a workaround for this issue?

Not doing any hot-restarting while development which is not ideal.

Risk:

What is the risk level of this cherry-pick?

  • Low
  • Medium
  • High

Test Coverage:

Are you confident that your fix is well-tested by automated tests?

  • Yes
  • No

Validation Steps:

What are the steps to validate that this fix works?

Running this app and hot restarting no longer prints null:

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  void initState() {
    super.initState();
    print('engineId: ${PlatformDispatcher.instance.engineId}');
  }
  // ...
}

@knopp
[shell] Fix engineId not being set after hot restart (flutter#174451)
94015af 
Fixes flutter#173474

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@flutteractionsbot flutteractionsbot added the cp: review Cherry-picks in the review queue label Sep 12, 2025
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flutteractionsbot commented Sep 12, 2025

@HosseinYousefi please fill out the PR description above, afterwards the release team will review this request.

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@github-actions github-actions bot added the engine flutter/engine related. See also e: labels. label Sep 12, 2025
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Code Review

This pull request fixes an issue where the engine ID was not being preserved during a hot restart. The changes correctly store the engine ID when an engine is run and re-apply it during hot restart. The change to use std::optional<int64_t> for the engine ID in RunConfiguration is a good improvement for API consistency and robustness. A test case has been added to verify the new behavior. I have one suggestion to improve test coverage for the case where no engine ID is provided.

engine/src/flutter/shell/common/shell_unittests.cc
Comment on lines +4921 to +4928
latch.Reset();

fml::TaskRunner::RunNowOrPostTask(
shell->GetTaskRunners().GetUITaskRunner(), [&]() {
ASSERT_EQ(shell->GetEngine()->GetLastEngineId(), 99);
latch.Signal();
});
latch.Wait();
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medium

This is a good test for the case where an engine ID is provided. To make the test coverage more complete, consider also testing the case where no engine ID is provided. You could add a similar check to the ProvidesNullEngineId test to assert that GetLastEngineId() returns std::nullopt in that scenario.

@matanlurey matanlurey added the autosubmit Merge PR when tree becomes green via auto submit App label Sep 12, 2025
@auto-submit auto-submit bot merged commit 4b9cc6e into flutter:flutter-3.35-candidate.0 Sep 12, 2025
161 checks passed
engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Sep 17, 2025
@engine-flutter-autoroll
4b9cc6e10 [CP-stable][shell] Fix engineId not being set after hot res…
a946252 
…tart (flutter/flutter#175255)
@reidbaker reidbaker mentioned this pull request Oct 1, 2025
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