Improve hint for installing meson-python when missing as build backend

[tobiasdiez]

Summary

If a package uses meson-python as backend, it's declared as:

[build-system]
build-backend = 'mesonpy'
requires = ['meson-python']

Currently, if meson-python is missing, one gets the following hint:

Traceback (most recent call last):
        File "<string>", line 8, in <module>
          import mesonpy as backend
      ModuleNotFoundError: No module named 'mesonpy'

      hint: This error likely indicates that `sagemath` depends on `mesonpy`, but doesn't declare it as a build
      dependency. If `sagemath` is a first-party package, consider adding `mesonpy` to its `build-system.requires`.
      Otherwise, either add it to your `pyproject.toml` under:

      [tool.uv.extra-build-dependencies]
      sagemath = ["mesonpy"]

      or `uv pip install mesonpy` into the environment and re-run with `--no-build-isolation`.

which is not quite correct as the build backend/module is called "mesonpy" but the python package one has to install is "meson-python". This hint is improved in this PR.

Test Plan

I didn't yet had a chance to setup a local dev env for testing this.

[zanieb]

We shouldn't hard-code this. The mapping should be performed at

uv/crates/uv-build-frontend/src/error.rs

Lines 403 to 406 in 35a8dd5

	let package_name = match crate::pipreqs::MODULE_MAPPING.lookup(module_name) {
	Some(package) => package.to_string(),
	None => module_name.to_string(),
	};

Maybe it's not right in our embedded mapping?

[zanieb]

It looks like it's just not present in crates/uv-build-frontend/src/pipreqs/mapping

[samypr100]

It looks like it's just not present in crates/uv-build-frontend/src/pipreqs/mapping

Is it worth adding it to https://github.com/bndr/pipreqs/blob/master/pipreqs/mapping and then syncing/update uv's version?

[zanieb]

That seems like the most proper way to do it, yeah.

[tobiasdiez]

I've now created a PR that adds the mapping upstream (bndr/pipreqs#508) and also updated the mapping here in the repo. Is this what you had in mind?

[tobiasdiez]

@zanieb @samypr100 The upstream PR bndr/pipreqs#508 was just merged. Is there anything I can/should do now to get this update into uv?

[zanieb]

Thanks!