[CP-stable]Don't throw an exception if no web define variable is set#182549
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auto-submit[bot] merged 1 commit intoflutter:flutter-3.41-candidate.0from Feb 18, 2026
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…2273) <!-- Thanks for filing a pull request! Reviewers are typically assigned within a week of filing a request. To learn more about code review, see our documentation on Tree Hygiene: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md --> This PR fixes a problem introduced in flutter#175805 that caused a build to exception to be thrown if variables like `{{this}}` were defined in the web `index.html`, but were not explicitly set by `--web-define=this=VALUE`. Resolves flutter#182243 Note: As per flutter#182076, this will always show the warning if ran with `flutter build web`, whereas `flutter run -d ...` works fine, regardless of whether you've set the variable or not. That is set to be fixed in flutter#182079, and does not have to do with this PR. ## Pre-launch Checklist - [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [x] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [x] I signed the [CLA]. - [x] I listed at least one issue that this PR fixes in the description above. - [x] I updated/added relevant documentation (doc comments with `///`). - [x] I added new tests to check the change I am making, or this PR is [test-exempt]. - [x] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [x] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord]. **Note**: The Flutter team is currently trialing the use of [Gemini Code Assist for GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code). Comments from the `gemini-code-assist` bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed. <!-- Links --> [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md --------- Co-authored-by: Navaron Bracke <[email protected]>
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This pull request changes the behavior for missing --web-define variables. Instead of throwing an exception and failing the build, it now logs a warning and continues, leaving the placeholder in the template. This is a quality-of-life improvement for developers. The implementation involves passing a logger to the template substitution logic and replacing throwToolExit with logger.printWarning. The associated command-line help text and tests have been updated to reflect this new behavior.
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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?
#182243
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 of production apps (the app crashes on launch).
This information is for domain experts and release engineers to understand the consequences of saying yes or no to the cherry pick.
flutter build webis broken for apps that use the{{...}}pattern inweb/index.html.Changelog Description:
Explain this cherry pick:
See best practices for examples.
Don't throw an exception if no web define variable is set.
Workaround:
Is there a workaround for this issue?
It's possible to workaround this issue by adding
--web-define=foo={{foo}}.Risk:
What is the risk level of this cherry-pick?
Test Coverage:
Are you confident that your fix is well-tested by automated tests?
Validation Steps:
What are the steps to validate that this fix works?
Follow repro steps in #182243