Add Open Policy Agent as a new language

[tsandall]

👋 hello!

I'd like to add syntax support for the Open Policy Agent (OPA) project. OPA is hosted by the Cloud Native Compute Foundation (CNCF). OPA implements a domain-agnostic policy language. It embodies policy-as-code, which means organizations often store, review, test, and revise their policies on GitHub.

Checklist:

• I am adding a new language.
  • The extension of the new language is used in hundreds of repositories on GitHub.com.
    • I ran the harvester tool and found Rego files in 79 252 public repositories (as of this PR).
    • Search results for each extension:
      • https://github.com/search?utf8=%E2%9C%93&type=Code&ref=searchresults&q=extension%3Arego+package+NOT+nothack
    • OPA policies start with a "package" directive that namespaces the rules (hence the search term above)
  • I have included a real-world usage sample for all extensions added in this PR:
    • The sample sources come from the OPA documentation. OPA is ALv2. They come come here (HTTP), here (Kafka), here (SSH), and here (K8s).
  • I have included a syntax highlighting grammar: https://github-lightshow.herokuapp.com/?utf8=%E2%9C%93&scope=from-url&grammar_format=auto&grammar_url=https%3A%2F%2Fraw.githubusercontent.com%2Ftsandall%2Fvscode-opa%2Fmaster%2Fsyntaxes%2FRego.tmLanguage&grammar_text=&code_source=from-url&code_url=https%3A%2F%2Fgithub.com%2Fopen-policy-agent%2Flibrary%2Fblob%2Fmaster%2Fterraform%2Fexample.rego&code=
  • There are no other languages with the same extension (.rego) in languages.yml.

[pchaigno]

Thanks for the neat pull request!

Unfortunately, as you noticed, usage is currently too low to meet our requirement of hundreds of repositories. We'll probably have to close this and reopen once adoption is high enough.
How old is OPA? Do you expect usage to grow in the near future?

[tsandall]

Thanks for the quick reply.

How old is OPA?

Started in early 2016.

Do you expect usage to grow in the near future?

Yes, the end-user community has grown quite a bit over the last year and a half. There are a number of companies running OPA (in production) today. We're also seeing other open source projects embedding & building on top of OPA.

usage is currently too low to meet our requirement of hundreds of repositories.

That's fair! We were hoping that since the growth is there and the extension was not taken, that an exception could be made 😅 I know lots of folks who have .rego files in private repos that would be happy to see this land :D

[pchaigno]

Ok. I'll add it to #4219 when I get back to a decent workstation (probably next week); I'll flag as Pending popularity in the meantime. That way we can monitor progress on adoption and it shouldn't be long before we can support it in Linguist.

[pchaigno]

Closing in favor of #4219. We'll monitor the popularity of the extension there. I'll try to check popularity again in ~6 months and I'll post here if usage grows enough to warrant support in Linguist.

[tsandall]

👋 @pchaigno could you re-run the popularity check? It's been a few months and we've seen growth (>200 repos now by my count).

[pchaigno]

You're right! The .rego file extension is now popular enough for inclusion (see #4219). @tsandall Do you want me to reopen this pull request or would you prefer to resubmit as a new pull request?

[tsandall]

@pchaigno this PR is fine. The only thing I'm unsure of is the language ID in the PR. Does that need to be regenerated?

[pchaigno]

No. If you used the script to generate the language ID the first time, there's no need to regenerate it.

[tsandall]

@pchaigno I've amended the commit to resolve the conflicts and fix the test failures. Let me know if anything else has to be done to land this.

[pchaigno]

Could you link in the template to where exactly you took the sample files from? Otherwise, LGTM.

[tsandall]

@pchaigno done! I updated the k8s one because that changed in the OPA docs. Should be ready to merge now.

[tsandall]

@pchaigno can this be merged now?