rubocop: add shim and command.

[MikeMcQuaid]

Add a shim and a command that can be used to easily add a single directory to your PATH (Library/Homebrew/shims/gems) and have it automatically install, configure and run rubocop so you can use it for in-editor integrations.

CC @Rylan12 who talked about this with me. ideally we'd/you'd add a commit to this PR with the Visual Studio Code configuration to run this rubocop

[BrewTestBot]

Review period will end on 2021-01-07 at 15:23:01 UTC.

[Rylan12]

Just glancing at the changes (haven't tried anything locally yet) makes sense to me.

My limited vscode experience tells me that we can provide a .vscode directory in this repo with settings like these, but this (I believe) will only be effective if we open the root directory in vscode. What I mean is opening a single file (e.g. code $(brew --repo)/Library/Homebrew/cmd/uses.rb) won't inherit these settings.

Another option might be to set up a specific workspace file. Then, maybe provide a brew code command that will open the workspace? Just not totally sure what the right approach to providing a configuration is.

And we also want to give users the ability to modify the configuration for themselves without creating unstaged changes or accidentally committing configuration things in a PR.

[RandomDSdevel]

     Why wouldn't this be a developer command, @MikeMcQuaid?

[Rylan12]

Upon running brew rubocop, I get the following output. Not sure if this is an issue on my end or not:

❯ brew rubocop --version
warning: parser/current is loading parser/ruby26, which recognizes
warning: 2.6.6-compliant syntax, but you are running 2.6.3.
warning: please see https://github.com/whitequark/parser#compatibility-with-ruby-mri.
1.7.0

This warning also shows up in vscode unless ruby.rubocop.suppressRubocopWarnings is true.

To test, I ran gem uninstall rubocop and then ran brew rubocop on both files in this repo and some formula files from homebrew/core. I intentionally created a few style issues to check that everything works properly, and I found no issues.

I did notice that /usr/local/Homebrew/Library/Homebrew/shims/gems/rubocop is consistently slower than just rubocop. Probably because it's invoking brew. Looking at the output of time, the shim is around 0.2 seconds slower, but it was noticeable to me (especially in vscode).

---

One thing to note: both of these require adding some extensions to vscode. Not sure if we can provide a settings file that includes those or not.

I've also added a vscode settings file that works for me. Unfortunately, I couldn't figure out how to infer HOMEBREW_REPOSITORY so I hardcoded it as /usr/local/Library/Homebrew/shims/gems/. I tried using $(brew --repository)/Library/Homebrew/shims/gems/ with no luck.

I also found that if PATH is set to include Library/Homebrew/shims/gems and vscode is launched using the code CLI tool, the default settings will work correctly.

A note on this approach: this will likely cause issues if users have their own .vscode directory where they've saved their existing settings since the .vscode directory was ignored.

As I said, I'm not really sure what the best way to do things here is, so feel free to just revert/drop if what I'm pushing isn't helpful at all.

[MikeMcQuaid]

My limited vscode experience tells me that we can provide a .vscode directory in this repo with settings like these, but this (I believe) will only be effective if we open the root directory in vscode. What I mean is opening a single file (e.g. code $(brew --repo)/Library/Homebrew/cmd/uses.rb) won't inherit these settings.

Yup, I think that's typical and expected.

Upon running brew rubocop, I get the following output. Not sure if this is an issue on my end or not:

It's not, it's because we're using an old Ruby version and RuboCop is complaining about it.

I did notice that /usr/local/Homebrew/Library/Homebrew/shims/gems/rubocop is consistently slower than just rubocop. Probably because it's invoking brew. Looking at the output of time, the shim is around 0.2 seconds slower, but it was noticeable to me (especially in vscode).

Yeh, that's expected but necessary if we're going to have the same e.g. Ruby logic.

One thing to note: both of these require adding some extensions to vscode. Not sure if we can provide a settings file that includes those or not.

We can 🎉

I've also added a vscode settings file that works for me. Unfortunately, I couldn't figure out how to infer HOMEBREW_REPOSITORY so I hardcoded it as /usr/local/Library/Homebrew/shims/gems/. I tried using $(brew --repository)/Library/Homebrew/shims/gems/ with no luck.

We could try a relative path from the workspace root (or use a workspace variable).

I might be able to take a look at this but if I don't: no worries!

     Why wouldn't this be a developer command, @MikeMcQuaid?

It could be.

As I said, I'm not really sure what the best way to do things here is, so feel free to just revert/drop if what I'm pushing isn't helpful at all.

No, this is really helpful!

A note on this approach: this will likely cause issues if users have their own .vscode directory where they've saved their existing settings since the .vscode directory was ignored.

Yup, thing that's just something we'll need to accept may cause one-off issues.

I also found that if PATH is set to include Library/Homebrew/shims/gems and vscode is launched using the code CLI tool, the default settings will work correctly.

🎉

[MikeMcQuaid]

I've pushed fixes for all mentioned issues here. @Rylan12 can you see if this still works for you as expected?

[Rylan12]

Awesome! Don't know why I didn't try a relative path...

Anyway, I tested locally and everything appears to work just fine for me. Plus, I learned about the endwise extension (very cool).

[BrewTestBot]

Review period ended.

[MikeMcQuaid]

Thanks for the help @Rylan12!

[Rylan12]

Thank you for getting this going!