Revert "176989 unifiedCheckRunFlow flag removal"

[ievdokdm]

Reverts #5144

[jtmcdole]

Gota land the code before you land the flag delete :)

[gemini-code-assist]

Code Review

This pull request introduces a unified check run flow feature, allowing consolidated check runs for presubmit tests based on user-specific or global configuration flags. It updates the scheduler, build services, and subscription handlers to support this flow, alongside updating associated tests and fixing platform-related mock usages in the device doctor package. The code review feedback highlights a critical issue where the stage defaults incorrectly to CiStage.fusionTests instead of CiStage.genericTests for non-fusion repositories. Additionally, the reviewer recommends replacing unsafe null assertions (!) on pullRequest.user and pullRequest.user!.login with null-safe fallbacks across several files to prevent potential runtime crashes.

[gemini-code-assist]

Defaulting the stage to CiStage.fusionTests for non-fusion repositories (where slug != Config.flutterSlug) is incorrect and can cause mismatches when querying or updating staging documents in Firestore. It should default to CiStage.genericTests for non-fusion repositories.

Suggested change

	stage: stage ?? CiStage.fusionTests,
	stage:
	stage ??
	(slug == Config.flutterSlug
	? CiStage.fusionTests
	: CiStage.genericTests),

[gemini-code-assist]

Using the null assertion operator ! on pullRequest.user and pullRequest.user!.login can lead to runtime crashes if the user or login is null (e.g., for certain automated actions or deleted accounts). Use null-safe access with a fallback instead.

    if (dashboardChecks != null &&
        pullRequest != null &&
        config.flags.isUnifiedCheckRunFlowEnabledForUser(
          pullRequest.user?.login ?? '',
        )) {
      // Create the presubmit_guard and associated presubmit_job documents.
      log.info(
        'Storing UnifiedCheckRun data for ${slug.fullName}#${pullRequest.number} as it enabled for user ${pullRequest.user?.login}.',
      );

[gemini-code-assist]

Using the null assertion operator ! on pullRequest.user and pullRequest.user!.login can lead to runtime crashes if the user or login is null. Use null-safe access with a fallback instead.

Suggested change

	final isUnifiedCheckRunFlow = _config.flags
	.isUnifiedCheckRunFlowEnabledForUser(pullRequest.user!.login!);
	final isOrderedPresubmit = _config.flags.isOrderedPresubmitEnabledForUser(
	pullRequest.user!.login!,
	);
	final isUnifiedCheckRunFlow = _config.flags
	.isUnifiedCheckRunFlowEnabledForUser(pullRequest.user?.login ?? '');
	final isOrderedPresubmit = _config.flags.isOrderedPresubmitEnabledForUser(
	pullRequest.user?.login ?? '',
	);

[gemini-code-assist]

Using the null assertion operator ! on pullRequest.user and pullRequest.user!.login can lead to runtime crashes if the user or login is null. Use null-safe access with a fallback instead.

Suggested change

	final isUnifiedCheckRun = _config.flags.isUnifiedCheckRunFlowEnabledForUser(
	pullRequest.user!.login!,
	);
	final isUnifiedCheckRun = _config.flags.isUnifiedCheckRunFlowEnabledForUser(
	pullRequest.user?.login ?? '',
	);