util.decorateRequest should confirm error is a missing project ID error

[gajus]

A bug in the google-cloud package resulted in the following error:

Error: Sorry, we cannot connect to Cloud Services without a project ID. You may specify one with an environment variable named "GCLOUD_PROJECT". See https://googlecloudplatform.github.io/google-cloud-node/#/docs/guides/authentication for a detailed guide on creating an authenticated connection.
    at Object.<anonymous> (/Users/gajus/Documents/dev/applaudience/movie-editor/node_modules/google-cloud/node_modules/@google-cloud/common/src/util.js:55:29)
    at Module._compile (module.js:571:32)
    at Module._extensions..js (module.js:580:10)
    at Object.require.extensions.(anonymous function) [as .js] (/Users/gajus/Documents/dev/applaudience/movie-editor/node_modules/babel-register/lib/node.js:152:7)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.require (module.js:498:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (/Users/gajus/Documents/dev/applaudience/movie-editor/node_modules/google-cloud/node_modules/@google-cloud/common/src/service-object.js:32:12)

The reason I am getting this error is this code block:

        try {
          authenticatedReqOpts = util.decorateRequest(
            authenticatedReqOpts,
            extend({ projectId: authClient.projectId }, config)
          );
        } catch(e) {
          err = util.missingProjectIdError;
        }
      }

Here catch assumes that any error that occurred in try is equivalent to missingProjectIdError.

Instead of blindly assuming what is the error, use instanceof check and a custom error constructor, e.g. https://github.com/gajus/xfetch/blob/0d8cd012354b0bb8b67162f74b2a9e126d3bdabb/src/attemptRequest.js#L52-L67.

Furthermore, what made it hard to debug is the lack stack trace (raised a separate issue #2068).

[stephenplusplus]

What was the error that it mistook for a missing project ID error?

[gajus]

Raising another issue for that.

[gajus]

@stephenplusplus #2070