gax: stub-creation-time auth failure bypasses the API-call promise — application .catch() cannot intercept it (surfaces as uncaughtException)

[murad-mocart]

Environment

• google-gax 4.6.1 (resolved transitively via @google-cloud/logging 11.3.0)
• google-auth-library (as resolved by the above)
• Node.js v22.x, Linux/macOS

Summary

When credential resolution fails at stub creation time (e.g. GOOGLE_APPLICATION_CREDENTIALS points at a missing file), the failure does not propagate through the API call's returned promise. An application's .catch() on the API call never fires — instead the error surfaces as a process-level uncaughtException (and with no handler installed, kills the process).

Reproduction

// GOOGLE_APPLICATION_CREDENTIALS=/tmp/definitely-does-not-exist-credentials.json node repro.js
const { Logging } = require('@google-cloud/logging'); // any gax-based client reproduces

process.on('unhandledRejection', (e) => console.log('[unhandledRejection]', e.message));
process.on('uncaughtException', (e) => {
  console.log('[uncaughtException — should have been a promise rejection]', e.message);
  process.exit(0);
});

const log = new Logging().log('repro-log');
const entry = log.entry({ resource: { type: 'global' } }, { message: 'hello' });

log
  .write(entry)
  .then(() => console.log('[then] ok'))
  .catch((e) => console.log('[catch] caught as expected:', e.message)); // ← never runs

Observed output:

[uncaughtException — should have been a promise rejection] The file at /tmp/definitely-does-not-exist-credentials.json does not exist, or it is not a file. ENOENT: no such file or directory ...

Stack points into stub creation:

    at GoogleAuth._getApplicationCredentialsFromFilePath (google-auth-library/build/src/auth/googleauth.js:375)
    ...
    at GrpcClient.createStub (google-gax/build/src/grpc.js:318)

The explicit .catch() on the write promise never fires; unhandledRejection never fires either — the error bypasses the promise chain entirely. (Also reproduced in the client library's own wrapper: @google-cloud/logging's logging_service_v2_client.js has a throw err; in the stub-initialization path that re-throws outside any user-reachable promise.)

Expected

A credential/auth failure during lazy stub creation should reject the pending API-call promise(s), so application code can handle it (.catch(), retry, fallback) like any other API error.

Impact

Any long-running service that treats logging/telemetry as non-critical and wraps every call in try/catch (or .catch()) still crashes on boot-time/lazy-init auth misconfiguration — there is no userland way to intercept it short of a process-wide uncaughtException handler. We currently work around it by issuing a deliberate "pre-warm" write at startup so the failure happens at a controlled fail-fast point.