[infra] Flutter SDK version checking/updating automation

[pq]

CI/CD Automation: Automated Flutter SDK Version Bumping & Integrity Verification

Why This Matters

To ensure stable and reproducible builds, our CI/CD scripts are pinned to a specific stable version of the Flutter SDK in tool/provision_flutter.sh (see: #8951). Manually monitoring and upgrading this pin is tedious, while a rolling pin risks introducing silent test breakages.

This PR automates the maintenance of our pinned Flutter SDK version with safe, presubmit-verified upgrades, backed by compile-time integrity checks to prevent syntax or synchronization bugs.

Fixes: #8953

---

Proposed Changes

1. Automated Version-Pin Bumping

• [NEW] .github/workflows/update_flutter.yaml: Added a scheduled weekly GitHub Actions workflow (running every Monday at midnight) that:
  • Queries the official Flutter GCS manifest API for new stable releases.
  • Extracts and compares the latest version with our current pin inside tool/provision_flutter.sh.
  • If a newer version is available, it automatically edits the version constant in the script and opens a structured Pull Request so that standard presubmit checks run against the new version prior to merging.

2. Compile-Time Integrity Verification

• [NEW] testSrc/unit/io/flutter/CIIntegrityTest.java: Added a custom JUnit meta-test to enforce synchronization between the provisioning script and the GitHub Action:
  • testFlutterProvisioningScriptIntegrity(): Asserts tool/provision_flutter.sh exists and contains a valid semver-formatted FLUTTER_VERSION="..." constant.
  • testGitHubWorkflowRegexSync(): Asserts .github/workflows/update_flutter.yaml matches the exact constant pattern used in its search-and-replace step.
  • Why this is here: Prevents silent setup failures if a developer renames or reformats the version constant in the future.

---

Verification Results

1. JUnit Integrity Tests: Ran the integrity suite locally:

   ./gradlew test --tests io.flutter.CIIntegrityTest
   

Result: BUILD SUCCESSFUL (Both assertions compiled and passed successfully in 4 seconds).

2. Local Run:

Until this is landed the action can't be tested on GH but this verifies that it should work:

☁  flutter-intellij [infra_flutterSdkWorkflow] ⚡  # 1. Read the current pinned version from the script (should print 3.41.0)
CURRENT_VERSION=$(grep -E 'FLUTTER_VERSION="[0-9.]+"' tool/provision_flutter.sh | head -n 1 | cut -d'"' -f2)
echo "Current pinned version: $CURRENT_VERSION"
# 2. Query the live Flutter API for the latest stable release version (should print 3.41.9+)
LATEST_VERSION=$(curl -s https://storage.googleapis.com/flutter_infra_release/releases/releases_linux.json | jq -r '.releases | map(select(.channel == "stable"))[0].version')
echo "Latest stable version: $LATEST_VERSION"
# 3. Run the comparison and update logic
if [ "$CURRENT_VERSION" != "$LATEST_VERSION" ]; then
  echo "New stable version detected: $LATEST_VERSION. Updating script..."

  # Perform the replacement (cross-compatible sed for macOS)
  sed -i "" "s/FLUTTER_VERSION=\"$CURRENT_VERSION\"/FLUTTER_VERSION=\"$LATEST_VERSION\"/g" tool/provision_flutter.sh

  echo "Successfully updated! Checking file content:"
  grep "FLUTTER_VERSION=" tool/provision_flutter.sh
else
  echo "Flutter SDK is already up to date."
fi
Current pinned version: 3.41.0
Latest stable version: 3.41.9
New stable version detected: 3.41.9. Updating script...
Successfully updated! Checking file content:
  FLUTTER_VERSION="3.41.9"

---

Review the contribution guidelines below:

• I’ve reviewed the contributor guide and applied the relevant portions to this PR.
• I've included the required information in the description above.
• My up-to-date information is in the AUTHORS file.
• I've updated CHANGELOG.md if appropriate.

Contribution guidelines:

• See
  our contributor guide and
  the Flutter organization contributor guide
  for general expectations for PRs.
• Larger or significant changes should be discussed in an issue before creating a PR.
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  dart format.
• Java and Kotlin contributions should strive to follow Java and Kotlin best
  practices (discussion).

[gemini-code-assist]

Code Review

This pull request introduces CIIntegrityTest.java, a new meta-test suite designed to ensure synchronization between the Flutter SDK provisioning script and the automated GitHub Actions workflow. The feedback suggests aligning the version validation regex to be less restrictive and more consistent with the automation's expectations. Additionally, it is recommended to use a more robust pattern matching approach instead of simple string containment when verifying the GitHub workflow configuration.

[pq]

When this lands, I can manually trigger the action and we should see a PR to bump to 3.41.9.

[helin24]

Great!