Contribute a git hook to pre-commit.com

[katrinleinweber]

Update

A broader solution than discusses here can be found in lorenzwalthert/pre-commit-hooks.

Original post

I read in #452 that git integration is not a priority, but maybe a small hook that just styles the files that one has git added / staged would be a minimal, viable step into that direction. Maybe as a contribution to pre-commit.com?

Do you think it would be possible to shell-script styler in that way? I played around a bit, but ran into problems.

[katrinleinweber]

for f in $(git diff --name-only --cached | grep '.R')
do
	Rscript -e "styler::style_file($f)"
done

yields Error in dirname(path) : object 'R' not found. Probably, because the files are of course in an R/ subdirectory.

[lorenzwalthert]

Hi @katrinleinweber, thanks.

I read in #452 that git integration is not a priority

Thanks for considering old issues. I did not mean I am strictly against it, but I at least won't develop it myself. If I understand correctly, the git hock would not be implemented in the source code of styler, right? I think it's a cool thing. I am not sure but I believe you could simply defer the path expansion to R?

for f in $(git diff --name-only --cached | grep '.R')
do
	Rscript -e "styler::style_file(file.path('R', $f))"
done

It is unfortunate that pre-commit.com does not support R because the above script might have problems due portability across operation systems. Are you on Windows? I can try the script on my Mac. Maybe we can add support for R to pre-commit.com too, although that might be more work?

[katrinleinweber]

Thanks for contextualising the idea! Yes, that would certainly be more work.

the git hook would not be implemented in the source code of styler

I guessed so (over in pre-commit/pre-commit-hooks), but pre-commit's contributing docu says: "get the .pre-commit-hooks.yaml files added to popular linters". I guess that means styler as well ;-) OTOH, those files are present in so many more, normal projects.

Hm... I'll inquire about the process of adding R support on their end.

[katrinleinweber]

Apparently, they need an r.py file that acts as a module handling the hook installation & run within their Python package.

[asottile]

Exciting! Yeah the work to make this happen would be in two parts:

1. Implement r as a language in pre-commit
2. Add a .pre-commit-hooks.yaml file in this repository

Does styler provide an executable when installed? and/or what's the usual interface that people run tools written in R?

[lorenzwalthert]

If you mean a bash-like command when you say executable, the answer is no. I don't know of any R package that does so to be honest. In almost all cases, people execute tools written in R in the R console (e.g. when using RStudio) or they invoke R from the command line with Rscript -e "styler::style_file(...)".

[lorenzwalthert]

References

• Article about adding a pre-commit hook for scala source code formatter.
• https://ljvmiranda921.github.io/notebook/2018/06/21/precommits-using-black-and-flake8/
• Some example hocks: https://github.com/pre-commit/pre-commit-hooks

[michaelquinn32]

Pre-commits seem better placed somewhere like usethis, which contains development tools that wrap styler. Plus, that package already sets up a user's git for a project.

[bfgray3]

I'd like to add my vote in support of a pre-commit hook.

[jackwasey]

A less invasive approach would be simply to report whether files would be styled, thus preventing a commit. Since it is possible that styler could generate invalid code, at least some people would prefer a message, like codemeta gives, instead of doing it for you. It is also a slow process for a bigger package, although checking whether styling is needed is probably just as slow as actually performing it, until there is some caching in styler.