[AGP 9] Update AGP Error

[jesswrd]

AGP is ready to use. Developers should not be running into this error at all due to support that has been added for Built-in Kotlin #184836. But in the event that they do run into this error, they will be guided to the right docs.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the AI contribution guidelines and understand my responsibilities, or I am not using AI tools.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• I followed the breaking change policy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

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Note: The Flutter team is currently trialing the use of Gemini Code Assist for GitHub. 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.

[reidbaker]

"Developers should not be running into this error at all due to . " Due to what?

[reidbaker]

/gemini review

[gemini-code-assist]

Code Review

This pull request replaces the generic AGP 9 warning with specific documentation URLs and updated error messages in gradle_errors.dart, while updating the corresponding test suite. Feedback suggests restoring the file path in the Kotlin migration error message for consistency, correcting grammar and capitalization in the DSL opt-out message, and fixing a spacing mismatch in the test expectations to prevent test failures.

[gemini-code-assist]

For consistency with other error handlers in this file (like useNewAgpDslErrorHandler), please include the file path where the error occurred and adjust the spacing to group the resolution steps together. This aligns with the principle that error messages should be useful and consistent.

References

1. Error messages should be useful: Every error message is an opportunity to make someone love our product. ^(link)

[gemini-code-assist]

Add a comma after 'this' and capitalize 'Flutter' for better readability and correctness. This ensures the error message is professional and clear.

References

1. Error messages should be useful: Every error message is an opportunity to make someone love our product. ^(link)

[gemini-code-assist]

There is an extra leading space in this string which will cause the test to fail, as the source code does not have a space before 'This' (it follows a newline in a multiline string).

[gemini-code-assist]

Code Review

This pull request updates AGP 9 migration error messages in the Flutter tools by replacing a generic warning constant with specific documentation URLs for built-in Kotlin migration and new DSL opt-out. The review feedback suggests restoring the Gradle file path in the Kotlin plugin error message to maintain consistency and provide better context for developers. Additionally, there are suggestions to correct capitalization and punctuation in the DSL error message and to fix a leading space in a test expectation that would otherwise cause a test failure.

[gemini-code-assist]

The updated error message removes the path to the Gradle file where the failure occurred. Including the file path (appGradleFile.path) is helpful for developers to identify where the change is needed, and it maintains consistency with the error message in useNewAgpDslErrorHandler (line 712).

Suggested change

	globals.printBox('''
	${globals.logger.terminal.warningMark} Starting AGP 9+, the default has become built-in Kotlin.
	This results in a build failure when applying the kotlin-android plugin.
	To resolve this, migrate to built-in Kotlin.
	\nFor instructions on how to migrate, see: $kMigrateToBuiltInKotlinDocsUrl''', title: _boxTitle);
	final File appGradleFile = project.android.appGradleFile;
	globals.printBox('''
	${globals.logger.terminal.warningMark} Starting AGP 9+, the default has become built-in Kotlin.
	This results in a build failure when applying the kotlin-android plugin at ${appGradleFile.path}.
	To resolve this, migrate to built-in Kotlin.
	\nFor instructions on how to migrate, see: $kMigrateToBuiltInKotlinDocsUrl''', title: _boxTitle);

References

1. Error messages should be useful: Every error message is an opportunity to make someone love our product. ^(link)

[gemini-code-assist]

The sentence is missing a comma after "To resolve this" and "Flutter" should be capitalized for consistency with other error messages in the tool.

Suggested change

	\nTo resolve this update flutter or opt out of `android.newDsl`.
	\nTo resolve this, update Flutter or opt out of `android.newDsl`.

References

1. Optimize for readability: Code is read more often than it is written. ^(link)

[gemini-code-assist]

This expectation contains an unexpected leading space (' This results...'), which is inconsistent with the code on line 688 of gradle_errors.dart and with the other test case on line 1701. This will likely cause the test to fail.

Suggested change

	contains(' This results in a build failure when applying the kotlin-android plugin'),
	contains('This results in a build failure when applying the kotlin-android plugin'),

[jesswrd]

"Developers should not be running into this error at all due to . " Due to what?

done added link.