Integrate WCAGComplianceChecker into CI build pipeline
epic-screen-reader-support-complex-widgets-task-015 — Wire the WCAGComplianceChecker into the CI build pipeline so that it runs automatically on every pull request. Configure the runner to fail the build on critical violations (missing labels, contrast < 4.5:1) and emit warnings for non-critical issues. Produce a machine-readable JSON report and a human-readable summary comment on the pull request.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 3 - 413 tasks
Can start after Tier 2 completes
Implementation Notes
Use flutter test --tags wcag to scope the run to accessibility tests only — avoids running the full suite and keeps the job fast. The WCAGComplianceChecker scan should be invoked from a dedicated Dart script (tool/wcag_scan.dart) that can be run headlessly without a device; use flutter test with a WidgetTester rather than requiring a simulator. For the PR comment, use the GitHub Actions job summary (echo '...' >> $GITHUB_STEP_SUMMARY) as the primary output — it requires no extra token permissions. Only fall back to posting a PR comment if a GITHUB_TOKEN with pull-requests: write is available.
Structure the CI YAML with three steps: (1) setup Flutter + cache, (2) run wcag scan + write report artifact, (3) post summary. Keep the fail/warn threshold configurable via a wcag_config.yaml file at the repo root so teams can adjust severity rules without editing the workflow.
Testing Requirements
Validate the CI integration with three test scenarios executed manually before merging: (1) Open a PR containing a widget with a known missing label — confirm the job fails and the PR comment shows the violation. (2) Fix the violation and push — confirm the job passes and the PR comment updates to 'No critical violations'. (3) Introduce a warning-level violation only — confirm the job passes but the warning appears in the PR comment summary. Additionally, add a dry-run CI mode (WCAG_DRY_RUN=true) that always exits 0 but still produces the report, used in the CI config tests themselves.
Flutter does not natively enforce a focus trap within a bottom sheet or modal dialog in the semantic tree — VoiceOver and TalkBack can navigate outside the sheet to background content. Implementing a reliable focus trap requires overriding the semantic tree, which may conflict with the existing modal helper infrastructure in the app and require changes to shared components beyond this feature's scope.
Mitigation & Contingency
Mitigation: Prototype the focus trap on the first modal sheet implementation before building the remaining sheets. Evaluate Flutter's ExcludeSemantics and BlockSemantics widgets as the trap mechanism, and coordinate with the team owning the shared modal helpers to agree on a non-breaking integration point before writing production code.
Contingency: If a complete semantic focus trap cannot be implemented without breaking existing modal patterns, implement a partial solution using FocusScope with autofocus on the modal's first element and a prominent 'Return to main content' semantic action, documenting the deviation from WCAG 2.4.3 with a scheduled remediation item.
The activity wizard uses BLoC state management and the UI rebuilds the entire step widget subtree on transition. If the semantic tree is traversed by VoiceOver before the build cycle settles, focus may land on a stale or partially rendered step, causing the wrong step label or progress value to be announced. This is particularly problematic for blind users who cannot visually verify the announcement against the screen.
Mitigation & Contingency
Mitigation: Coordinate ActivityWizardStepSemantics with FocusManagementService (from the core services epic) to delay focus placement until the post-build callback confirms the new step's semantic tree is complete. Write integration tests using the AccessibilityTestHarness that assert the full announcement sequence across all five wizard steps.
Contingency: If post-build focus delay is insufficient due to async BLoC emission timing, add an explicit semantic notification barrier in the wizard cubit that emits a 'step ready' event only after the new widget tree has been marked as built, decoupling the announcement trigger from the raw state transition.
Automated WCAG contrast ratio checking on widget tree snapshots may produce false positives for gradient backgrounds, dark-mode overrides, or design token overrides that are resolved at runtime but appear as unresolvable colours at static analysis time. Excessive false positives would erode team trust in the CI gate, leading to suppression rules that also mask real violations.
Mitigation & Contingency
Mitigation: Scope the WCAGComplianceChecker to check only solid-colour backgrounds in the first iteration, explicitly excluding gradients from contrast checks with documented rationale. Design the check output to distinguish 'undetermined' (gradient/unknown) from 'fail' (solid colour below threshold) so the team can take targeted action on genuine failures only.
Contingency: If false positive rates exceed 20% of reported violations during initial CI runs, switch the CI gate from a hard build failure to a warning annotation on the pull request, combined with a mandatory manual review step, until the checker's rule set has been tuned to match actual design token values.