API key authentication doesn't work for Cloud Natural Language

[anotheri]

Environment details

• OS: Ubuntu
• Node.js version: 8.1.4
• npm version: 5.0.3
• "@google-cloud/language": "^0.11.0"

Steps to reproduce

  const language = require( '@google-cloud/language' )( {
    projectId: <MY_PROJECT_ID>,
    key: <MY_API_KEY>
  } );

It throws:

UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): 
Error: Could not load the default credentials. 
Browse to https://developers.google.com/accounts/docs/application-default-credentials 
for more information.

It works with credentials object and with config json file, but it fails with API key.
Please advise or fix.

[anotheri]

And it looks like API key auth doesn't work for other packages as well, see: #1424

[lukesneeringer]

This is something that just got a decent bit of discussion internally on the Python side, where we did have support and actively removed it. Essentially, API keys are a discouraged form of authentication at this point, and we do not intend to support them in client libraries.

[anotheri]

@lukesneeringer thanks for the answer; that'd be super helpful to add a clear note that API key auth is not supported in the documentation then.