[camera_avfoundation] Handle startWriting errors

[rickhohler]

Fixes flutter/flutter#180048.

This PR adds error handling for AVAssetWriter.startWriting in camera_avfoundation. Previously, the boolean return value was ignored, which could mask initialization errors. Now, a FlutterError is returned if writing fails to start.

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or I have commented below to indicate which version change exemption this PR falls under¹.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

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Footnotes

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[gemini-code-assist]

Code Review

This pull request correctly adds error handling for AVAssetWriter.startWriting in camera_avfoundation. Previously, the boolean return value was ignored, which could lead to silent failures during video recording initialization. The change ensures that if startWriting returns false, a FlutterError is created with details from the writer's error property and passed to the completion handler. This prevents the camera from entering an incorrect isRecording state. A new unit test is added to verify this new error handling path, and the isRecording property's access level was updated to private(set) to allow for assertions in the test.

[stuartmorgan-g]

Thanks for the contribution!

In the future, please do not delete the checklist that is in the PR template; it is there for a reason. This PR is missing required elements described in the checklist (I’ve restored it to the PR description), which need to be addressed before it moves forward with review.

I am marking the PR as a Draft. Please review the checklist, updating the PR as appropriate, and when that’s complete please feel free to mark the PR as ready for review.

[gemini-code-assist]

Code Review

This pull request introduces error handling for AVAssetWriter.startWriting in camera_avfoundation. Previously, the boolean return value was ignored, potentially masking initialization errors. The change correctly checks this return value and propagates a FlutterError if the operation fails. A corresponding unit test has been added to validate the new error handling logic, and the isRecording property's visibility was adjusted to private(set) to facilitate testing. The changes are well-implemented, and I have one suggestion to further improve the code's robustness.

[rickhohler]

Thanks! I've confirmed the checklist is complete and applied the suggested code improvement. Marking ready for review.

[stuartmorgan-g]

I've confirmed the checklist is complete

As with your other PR, the version changes aren't in the PR.

[rickhohler]

Apologies for the oversight. I have bumped the version to 0.9.22+10 and added the corresponding CHANGELOG entry.

Additionally, I updated the isRecording property to private(set) to correctly facilitate testing as noted in the review.

Ready for another look!