Ability to inline JSON into GOOGLE_APPLICATION_CREDENTIALS

[jart]

Some CI systems don't really give you the option to have files. Since we're not sure yet if it would be a good idea to allow the user to configure the default instance of CloudStorageFileSystemProvider with a Storage object that has custom authentication, it would be really nice if the environment variable provided greater flexibility.

I propose that, if the GOOGLE_APPLICATION_CREDENTIALS environment has a value that:

1. Starts with ^\s*\{
2. Is valid JSON

Then it will be treated as though it's the contents of the key file, rather than a filename.

@aozarov @jean-philippe-martin

[jean-philippe-martin]

It sounds nice. One potential caveat is that we're not the only people accepting this variable. Users might be confused and start using our method with other languages or in other libraries and get errors.
Instead, we could leave the createApplicationDefaults() call (or moral equivalent) unchanged and instead allow our users to find their way to the createForJson(InputStream jsonCredentialStream) method.

[jart]

In that case, how do we escalate this bug so it applies to all projects that use GOOGLE_APPLICATION_CREDENTIALS? Should we file a bug on https://github.com/GoogleCloudPlatform/gcloud-common?

[mziccard]

I agree this is a much needed feature. However GOOGLE_APPLICATION_CREDENTIALS are used and documented also elsewhere. I fear that changing this convention in the "sole" gcloud-* world might be confusing. \cc @jgeewax @aozarov

[mziccard]

This has been open for a while but as per my previous comment this is not something we can change.

[mgoddard-pivotal]

I am looking into using the Cloud Natural Language API for some applications which will be run in Cloud Foundry. Google has built a service broker, so I can "bind" my app to an "instance" of the GCP NLP API and, from that, I can get the JSON string which could be contained within a file which I see referenced by GOOGLE_APPLICATION_CREDENTIALS. The example I'm looking to use is here:

https://github.com/GoogleCloudPlatform/java-docs-samples/tree/master/language

Based on this example, if I can set GOOGLE_APPLICATION_CREDENTIALS to the path to this JSON file, all is well. If, however, all I have is the string containing the JSON, it's not apparent how I proceed as there is no such example within the repo I mention here. Could anyone here offer an alternative?

Thanks!

Mike