feat(functions): avoid blocking on missing v2 source tokens

[kdawgwilk]

Add an optional timeout to SourceTokenScraper so callers can bail out when a
source token never returns. Use a 2s cap in v2 create/update paths to keep
builds running in parallel, while still reusing tokens when available. Add a
spec covering the timeout behavior.

[gemini-code-assist]

Summary of Changes

Hello @kdawgwilk, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the robustness of Google Cloud Functions v2 deployments by preventing indefinite blocking when the backend fails to return a source token. It introduces a timeout mechanism to the SourceTokenScraper, ensuring that deployment processes can continue without waiting indefinitely, thereby improving overall build efficiency and resilience against transient backend issues.

Highlights

• Timeout for SourceTokenScraper: An optional timeoutMs parameter has been added to the SourceTokenScraper's getToken method, allowing callers to specify a maximum waiting time for a source token before proceeding.
• GCFv2 Deployment Resilience: A 2-second timeout (SOURCE_TOKEN_FETCH_TIMEOUT_MS) is now applied to getToken calls during Google Cloud Functions v2 creation and update processes, preventing builds from blocking indefinitely if a source token is not returned promptly.
• Timeout Logic Implementation: A new private helper method, waitForToken, has been introduced within SourceTokenScraper to manage the timeout logic using Promise.race, ensuring efficient handling of token fetching.
• New Test Coverage: A new test case has been added to sourceTokenScraper.spec.ts to specifically validate the early return behavior of getToken when a timeout is configured, ensuring the functionality works as expected.

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[gemini-code-assist]

Code Review

This pull request introduces a timeout mechanism to the SourceTokenScraper to prevent deployments from getting stuck when a source token isn't returned by the backend. This is a valuable improvement for deployment reliability. The implementation correctly uses Promise.race for the timeout and applies it to GCFv2 function creation and updates. The added test case effectively validates the new timeout behavior. I have one suggestion to improve code maintainability by reducing some duplication.