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clang-format support #59

Closed bdice closed 3 years ago

bdice commented 3 years ago

Hi! I'm interested in adding clang-format to the container used for pre-commit. However, it's possible that there is a better solution to my problem, so I want to give a little more info about the challenge I'm facing in hopes of finding a simpler approach. If there isn't a better way, then I would like to make a PR to add clang-format to this container.

I work on a couple Python/C++ projects. We use pre-commit for all the Python hooks, but our C++ hooks are harder to install (e.g. clang-format). While there are several hooks for clang-format, all of those hooks require clang-format to be installed on the system (they're local hooks and there's not a way to install clang-format in a virtual environment that I've seen). For now, we've been splitting our hooks into two files that run on our CI:

  1. .pre-commit-config.yaml contains all the hooks with dependencies that can be installed by pre-commit. These are always installed and run on user machines as long as the user installs pre-commit.
  2. .pre-commit-config-cpp.yaml contains the C++ hooks that require more tools to be installed. These will fail unless the user does extra work to acquire clang-format, etc. The only C++ hook that I really care about is clang-format, the rest aren't as important.

I'd like to be able to use pre-commit.ci to automatically apply clang-format. If pre-commit.ci had clang-format available in the container, I could combine the two config files and just let it run on CI (without worrying about whether users have clang-format installed locally, since their PRs can be auto-fixed). Ideally there would be a way that users could execute the Python/general hooks locally and skip the C++ hooks if they don't have the right tools installed. Any advice would be welcome! Thanks for your amazing work on pre-commit and the CI service. Hoping to tune into a live stream sometime soon. 😄

asottile commented 3 years ago

pre-commit (and by extension) pre-commit.ci works best when it manages your tools. language: system is the escape hatch for manual management and is not supported for pre-commit.ci at the current time.

installing global tools inside the container goes against the intent that a user should not need to set up anything to run the tools. ideally there'd be a first-class supported way to run clang-format via one of the currently supported languages (an example for a workaround (pre-commit doesn't directly support haskell at the moment) is https://github.com/shellcheck-py/shellcheck-py -- this wraps the shellcheck binary in a tiny python package which downloads a prebuilt binary.

There's also some work that's being done to make download a language that might interest you: https://github.com/pre-commit/pre-commit/issues/1453

additionally there's planned paid-tier extensions that would allow something like this: https://github.com/pre-commit-ci/issues/issues/13 (it would likely be a fixed set of system tools that could be added on to the running image)

asottile commented 3 years ago

(moving this issue since I noticed it's in the wrong place)

asottile commented 3 years ago

the other thing you can do today if you don't want to split up your configuration files is to utilize ci: skip for now

bdice commented 3 years ago

I appreciate the info and links! We'll probably keep the separate configs for now, since we want local pre-commit hooks to skip clang-format as well (only want to run it manually through the second config on developer systems with clang-format, or on our CI image with clang-format installed). I'll close this issue since my questions have been answered, and thank you for your time. 👍