How to best run linters/autoformatters on a template with pre-commit?

[cmarqu]

It can be quite tedious getting a Jinja template to the point where the whitespace it generates passes strict linters and autoformatters like ruff for Python.
Ideally, a pre-commit plugin/hook would exist that helps with this task.

How are people generally dealing with this?

Creating a autoformatter pre-commit hook that runs Jinja on-the-fly on each file to make sure the Jinja macros are not interfering with target language constructs would be possible, but the need to "backport" formatting changes to the template probably makes this tricky to get right.
Has someone already attempted that?

I assume one could also just ignore the problem and always run the autoformatter on generated code,
but some more obscure languages do not even have such a tool.

[sisp]

I assume one could also just ignore the problem and always run the autoformatter on generated code,
but some more obscure languages do not even have such a tool.

That's exactly how I'm doing it. My templates include pre-commit, and I maintain a rather comprehensive test suite using pytest to check generated projects (mostly files/directories and contents), and at least one test is a full integration test that installs dependencies, runs the generated project's test suite, and runs pre-commit on the generated project. I can't imagine how a linter could properly deal with Jinja-templated files.

[cmarqu]

Thanks for the quick reply.
Are you using tasks to run the autoformatters and accept that you have to use the --trust option, or something else?

[pawamoy]

For me, basically, a Makefile within the generated project.

copier copy template tmpproject
cd tmpproject
make install
make lint

[pawamoy]

One limitation is that I can't auto-format the template files. But I can print a diff pretty easily:

copier copy template tmpproject
cd tmpproject
git init
git add -A
git commit -m whatever
make install
make format
git diff

...and fix the formatting manually in the templated files.

[cmarqu]

@pawamoy Ah, so you do make the template files clean. This is where I am at right now, but I was thinking of not bothering with that at all and just run a formatter post-copier copy using _tasks. Template users then do not need to know about the whitespace skeletons in the closet as long as they --trust :)

[sisp]

I make sure that generated files pass the formatters and linters without modification. This may be a bit more work as a template author, but it avoids the prerequisite of a properly set up environment for executing the formatter; this way, project generation and toolchain setup are two separate concerns. That said, updating a project generally requires a post-update run of the formatter in case its rules and/or config have changed after the update. But so far, I expect this step to be performed manually rather than using a post-update migration task.