Automatic code formatting in PRs

[jrhemstad]

We want an easy, automatic system for checking code in a PR is consistent with our .clang-format as well as applying the appropriate formatting.

An important part of maintaining a consistent formatting is using the identical version of the clang-format binary everywhere. We can address this by including a consistent version in all of our devcontainers.

However, for the convenience of external contributors, we should also have a way to automatically format the code without requiring them to format it locally. One option would be to have an action that automatically checks if the code is formatted correctly and immediately commits to the PR with the correctly formatted code.

However, this may be surprising to people to have commits automatically added to their PR without manual intervention. As a compromise, we should still add a Action to verify the code is formatted, but instead of automatically applying the formatting, we add a /format slash command that will format the code and apply a commit to the PR.

Tasks

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1. [FEA]: Evaluate using pre-commit for linter management #1588
   feature request +1
   
2. Setup pre-commit.ci for automated linter enforcement and applying changes #1589
   +0

[miscco]

I believe this is essentially blocked on us providing a explicit formatter in the devcontainer and configure it such that formatting is enabled in the repo.

Looking at the llvm feature we are currently installing all packages. @trxcllnt would it be feasible to create a "clang-format" feature?

What I really want to avoid is that the llvm-16 devcontainer requires different formatting than the llvm-7 devcontainer because it uses different clang-format binaries.

Furthermore, if we enable code checking as part of CI we need to also provide a way for users to automagically do this. I do not care the slightest whether we use cmake-format or a pre-commit hook or whatever, but it must be frictionless to use within all our devcontainers

[jrhemstad]

I believe this is essentially blocked on us providing a explicit formatter in the devcontainer

Yep, that's the first item in #455

What I really want to avoid is that the llvm-16 devcontainer requires different formatting than the llvm-7 devcontainer because it uses different clang-format binaries.

Indeed. We'll install the latest version of clang-format in all the images.

provide a way for users to automagically do this

That's what the slash command is for 🙂.

[miscco]

I meant to do it locally and not in CI later

[jrhemstad]

Local formatting will be done with devcontainers. If people don't want to use devcontainers, then we'll have the slash command.

[trxcllnt]

Yeah, I can make the LLVM feature only install a subset of the packages. Then we can define it multiple times with different versions and package subsets. I just did this with the CUDA feature so we could layer in cuTensor, cuDNN, etc. So this shouldn't be too difficult.