Improve error handling for App Hosting compute service account

[blidd-google]

Follow-up to #8785. Improves error handling and messaging and adds a unit test to make sure the CLI throws if it encounters an unexpected error while trying to create the compute service account.

[gemini-code-assist]

Summary of Changes

Hello @blidd-google, 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 focuses on enhancing the robustness and user experience around the App Hosting compute service account creation process. It refines error handling logic to ensure unexpected issues are properly propagated, improves user-facing messages for provisioning states, and adds a dedicated unit test to validate these error handling improvements.

Highlights

• Improved Error Handling: The core logic for ensuring the App Hosting compute service account (ensureAppHostingComputeServiceAccount) has been refined to better distinguish between expected (e.g., 403 for permission issues, 404 for not found) and unexpected errors, ensuring that unexpected errors are properly re-thrown and not silently swallowed.
• Enhanced User Messaging: The warning message displayed when the App Hosting compute service account is still provisioning (HTTP 400 status) has been updated to provide clearer guidance to the user, suggesting they try again if an error occurs.
• New Unit Test: A new unit test has been added to backend.spec.ts specifically to verify that the CLI correctly throws an error when an unexpected status (e.g., 500) is encountered during the service account permission checks.
• Refactored Error Flow: The prepare.ts file has been simplified by removing a redundant try-catch block around the ensureAppHostingComputeServiceAccount call. This centralizes the error handling for service account provisioning within backend.ts, making the overall flow cleaner and more maintainable.

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[gemini-code-assist]

Code Review

This pull request enhances error handling for the App Hosting compute service account by refactoring error logic, improving a warning message, adding a unit test, and centralizing error handling. The changes improve code robustness and clarity.

[gemini-code-assist]

Throwing the error directly might obscure the original error's context. Consider logging the error or including it as an original property in a new FirebaseError object to preserve the stack trace and debugging information.

    } else {
      // Log the unexpected error for debugging purposes.
      console.error("Unexpected error:", err);
      // Re-throw the error, possibly wrapping it in a FirebaseError to add context.
      throw new FirebaseError("Unexpected error during service account check", { original: err });
    }