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[flutter_driver] Don't throw when stderr is unavailable on web#187190

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flutter-zl:issue_186751_driver_stderr_web
Jun 2, 2026
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[flutter_driver] Don't throw when stderr is unavailable on web#187190
auto-submit[bot] merged 2 commits into
flutter:masterfrom
flutter-zl:issue_186751_driver_stderr_web

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@flutter-zl flutter-zl commented May 27, 2026 •
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Fixes #186751

Problem
flutter_driver's default logger calls stderr.writeln. On web (DDC), even reading stderr
throws UnsupportedError, so any driver error path in a web target app crashes the logger and
the request times out.

Fix
Catch UnsupportedError and fall back to print, which DDC routes to the browser console.
Desktop and mobile paths unchanged.

@flutter-zl flutter-zl requested a review from mdebbar May 27, 2026 18:51
@flutter-dashboard flutter-dashboard Bot added the CICD Run CI/CD label May 27, 2026
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flutter-dashboard Bot commented May 27, 2026

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It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing. If you believe this PR qualifies for a test exemption, contact "@test-exemption-reviewer" in the #hackers channel in Discord (don't just cc them here, they won't see it!). The test exemption team is a small volunteer group, so all reviewers should feel empowered to ask for tests, without delegating that responsibility entirely to the test exemption group.

@github-actions github-actions Bot added a: tests "flutter test", flutter_test, or one of our tests framework flutter/packages/flutter repository. See also f: labels. labels May 27, 2026
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Code Review

This pull request updates the _defaultDriverLogger function in packages/flutter_driver/lib/src/common/error.dart to catch UnsupportedError. This fallback handles environments like the web where dart:io's stderr is not implemented, redirecting the log output to print so it reaches the browser console. There are no review comments to address.

@github-actions github-actions Bot removed the CICD Run CI/CD label May 27, 2026
@mdebbar mdebbar added the CICD Run CI/CD label Jun 1, 2026
@flutter-zl flutter-zl added the autosubmit Merge PR when tree becomes green via auto submit App label Jun 1, 2026
@auto-submit auto-submit Bot added this pull request to the merge queue Jun 1, 2026
Merged via the queue into flutter:master with commit 4917332 Jun 2, 2026
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@flutter-dashboard flutter-dashboard Bot removed the autosubmit Merge PR when tree becomes green via auto submit App label Jun 2, 2026
This was referenced Jun 2, 2026
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auto-submit Bot pushed a commit to flutter/packages that referenced this pull request Jun 2, 2026
@engine-flutter-autoroll
Roll Flutter from 54e199ac49e0 to 701665b97818 (26 revisions) (#11822)
783b25c 
flutter/flutter@54e199a...701665b

2026-06-02 engine-flutter-autoroll@skia.org Roll Skia from c97e939eb5c9 to 279b17fe9fc1 (16 revisions) (flutter/flutter#187425)
2026-06-02 bdero@google.com [Flutter GPU] Add block-compressed texture format support (BC, ETC2, ASTC LDR) (flutter/flutter#187281)
2026-06-02 bdero@google.com [Impeller] Allow attaching specific texture mip levels and slices (flutter/flutter#187066)
2026-06-02 bdero@google.com [Impeller] Fix GLES command submission status before context is current (flutter/flutter#187293)
2026-06-02 engine-flutter-autoroll@skia.org Roll Dart SDK from 3cdc25e8ffe9 to d39850bf4a01 (9 revisions) (flutter/flutter#187409)
2026-06-01 jason-simmons@users.noreply.github.com [Impeller] Use glVertexAttribDivisor on GLES3 and glVertexAttribDivisorEXT on GLES2 with the extension (flutter/flutter#187313)
2026-06-01 matt.boetger@gmail.com [Android] Add Javadoc documentation to TextInputChannel (flutter/flutter#186018)
2026-06-01 mvincentong@gmail.com Read FLTEnableWideGamut from Dart bundle (flutter/flutter#186509)
2026-06-01 matt.boetger@gmail.com [flutter_tools] Remove obsolete AndroidX console warning during Gradle builds (flutter/flutter#186077)
2026-06-01 kjlubick@users.noreply.github.com [skia] Update gni file list name hsw -> ml3 (flutter/flutter#184892)
2026-06-01 zhongliu88889@gmail.com [web] Always sync slider input attrs regardless of gesture mode (flutter/flutter#187217)
2026-06-01 zhongliu88889@gmail.com [flutter_driver] Don't throw when stderr is unavailable on web (flutter/flutter#187190)
2026-06-01 116356835+AbdeMohlbi@users.noreply.github.com Remove unused code in `FlutterPluginUtils.kt` (flutter/flutter#187012)
2026-06-01 taak140@gmail.com [flutter_tools] Fix `flutter drive --chrome-binary` being ignored on web (flutter/flutter#185481)
2026-06-01 davidmartos96@gmail.com Eager failure when building and no XCode build settings (flutter/flutter#184726)
2026-06-01 goung123@gmail.com Fix Windows Korean IME caret position during composition (flutter/flutter#186353)
2026-06-01 okorohelijah@google.com iOS: update provisioning profile for 2026-2027 cert (flutter/flutter#187280)
2026-06-01 154381524+flutteractionsbot@users.noreply.github.com Sync CHANGELOG.md from stable (flutter/flutter#187380)
2026-06-01 jason-simmons@users.noreply.github.com Reland "Move dart-lang/ai to a top level third party dependency in engine (#187268)" (flutter/flutter#187378)
2026-06-01 stuartmorgan@google.com Add vector_math to Framework triage (flutter/flutter#187389)
2026-06-01 engine-flutter-autoroll@skia.org Roll Packages from e930ced to f5d50ca (4 revisions) (flutter/flutter#187381)
2026-06-01 mr_nadeem_iqbal@yahoo.com [flutter_tools] Reject archive entries that escape into a sibling directory by name prefix (#185794) (flutter/flutter#186647)
2026-06-01 bkonyi@google.com [flutter_tools] Fix widget_preview unawaited async write race condition (flutter/flutter#187177)
2026-06-01 137456488+flutter-pub-roller-bot@users.noreply.github.com Roll pub packages (flutter/flutter#187375)
2026-06-01 engine-flutter-autoroll@skia.org Roll Skia from 0aee4675e0ad to c97e939eb5c9 (7 revisions) (flutter/flutter#187371)
2026-06-01 mr_nadeem_iqbal@yahoo.com docs: Stack.clipBehavior = Clip.none does not extend hit testing (#160787) (flutter/flutter#186643)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-packages
Please CC stuartmorgan@google.com,tarrinneal@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
creatorpiyush pushed a commit to creatorpiyush/packages that referenced this pull request Jun 10, 2026
@engine-flutter-autoroll
Roll Flutter from 54e199ac49e0 to 701665b97818 (26 revisions) (flutte…
a268273 
…r#11822)

flutter/flutter@54e199a...701665b

2026-06-02 engine-flutter-autoroll@skia.org Roll Skia from c97e939eb5c9 to 279b17fe9fc1 (16 revisions) (flutter/flutter#187425)
2026-06-02 bdero@google.com [Flutter GPU] Add block-compressed texture format support (BC, ETC2, ASTC LDR) (flutter/flutter#187281)
2026-06-02 bdero@google.com [Impeller] Allow attaching specific texture mip levels and slices (flutter/flutter#187066)
2026-06-02 bdero@google.com [Impeller] Fix GLES command submission status before context is current (flutter/flutter#187293)
2026-06-02 engine-flutter-autoroll@skia.org Roll Dart SDK from 3cdc25e8ffe9 to d39850bf4a01 (9 revisions) (flutter/flutter#187409)
2026-06-01 jason-simmons@users.noreply.github.com [Impeller] Use glVertexAttribDivisor on GLES3 and glVertexAttribDivisorEXT on GLES2 with the extension (flutter/flutter#187313)
2026-06-01 matt.boetger@gmail.com [Android] Add Javadoc documentation to TextInputChannel (flutter/flutter#186018)
2026-06-01 mvincentong@gmail.com Read FLTEnableWideGamut from Dart bundle (flutter/flutter#186509)
2026-06-01 matt.boetger@gmail.com [flutter_tools] Remove obsolete AndroidX console warning during Gradle builds (flutter/flutter#186077)
2026-06-01 kjlubick@users.noreply.github.com [skia] Update gni file list name hsw -> ml3 (flutter/flutter#184892)
2026-06-01 zhongliu88889@gmail.com [web] Always sync slider input attrs regardless of gesture mode (flutter/flutter#187217)
2026-06-01 zhongliu88889@gmail.com [flutter_driver] Don't throw when stderr is unavailable on web (flutter/flutter#187190)
2026-06-01 116356835+AbdeMohlbi@users.noreply.github.com Remove unused code in `FlutterPluginUtils.kt` (flutter/flutter#187012)
2026-06-01 taak140@gmail.com [flutter_tools] Fix `flutter drive --chrome-binary` being ignored on web (flutter/flutter#185481)
2026-06-01 davidmartos96@gmail.com Eager failure when building and no XCode build settings (flutter/flutter#184726)
2026-06-01 goung123@gmail.com Fix Windows Korean IME caret position during composition (flutter/flutter#186353)
2026-06-01 okorohelijah@google.com iOS: update provisioning profile for 2026-2027 cert (flutter/flutter#187280)
2026-06-01 154381524+flutteractionsbot@users.noreply.github.com Sync CHANGELOG.md from stable (flutter/flutter#187380)
2026-06-01 jason-simmons@users.noreply.github.com Reland "Move dart-lang/ai to a top level third party dependency in engine (#187268)" (flutter/flutter#187378)
2026-06-01 stuartmorgan@google.com Add vector_math to Framework triage (flutter/flutter#187389)
2026-06-01 engine-flutter-autoroll@skia.org Roll Packages from e930ced to f5d50ca (4 revisions) (flutter/flutter#187381)
2026-06-01 mr_nadeem_iqbal@yahoo.com [flutter_tools] Reject archive entries that escape into a sibling directory by name prefix (#185794) (flutter/flutter#186647)
2026-06-01 bkonyi@google.com [flutter_tools] Fix widget_preview unawaited async write race condition (flutter/flutter#187177)
2026-06-01 137456488+flutter-pub-roller-bot@users.noreply.github.com Roll pub packages (flutter/flutter#187375)
2026-06-01 engine-flutter-autoroll@skia.org Roll Skia from 0aee4675e0ad to c97e939eb5c9 (7 revisions) (flutter/flutter#187371)
2026-06-01 mr_nadeem_iqbal@yahoo.com docs: Stack.clipBehavior = Clip.none does not extend hit testing (#160787) (flutter/flutter#186643)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/flutter-packages
Please CC stuartmorgan@google.com,tarrinneal@google.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose

To report a problem with the AutoRoller itself, please file a bug:
https://issues.skia.org/issues/new?component=1389291&template=1850622

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md
via-guy pushed a commit to via-guy/flutter that referenced this pull request Jun 26, 2026
@flutter-zl @via-guy
[flutter_driver] Don't throw when stderr is unavailable on web (flutt…
8113231 
…er#187190)

**Fixes flutter#186751**

  **Problem**
`flutter_driver`'s default logger calls `stderr.writeln`. On web (DDC),
even reading `stderr`
throws `UnsupportedError`, so any driver error path in a web target app
crashes the logger and
  the request times out.

  **Fix**
Catch `UnsupportedError` and fall back to `print`, which DDC routes to
the browser console.
  Desktop and mobile paths unchanged.
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Flutter driver error logger assumes stderr which breaks web

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