feat: Support for optional python_site_packages_path in repodata

[jjhelmus]

Add support for the optional python_site_packages_path field that can appear in repodata for python packages as a means to specify the location of the site-packages directory.

This optional field is defined in CEP-17.

partial implementation for #3558

Please be kind as this is my first contribution to mamba and the first time digging into the source.

[jjhelmus]

This is likely not a complete implementation for CEP-17 in mamba but may be enough to unblock libmamba-conda-solver (see conda/conda-libmamba-solver#560).

This is rough and likely needs some work to finish things up but was hoping for initial feedback (or someone else to take over 😄).

With these changes I was able to get the field to show up in the output of repoquery search:

./build/micromamba/mamba repoquery search -c jjhelmus/label/sp_path python=3.99.99  --json | jq .result.pkgs
[
  {
    "build": "0",
    "build_number": 0,
    "build_string": "0",
    "channel": "jjhelmus",
    "constrains": [],
    "depends": [
      "pip"
    ],
    "fn": "python-3.99.99-0.tar.bz2",
    "license": "",
    "md5": "2570015e0cb5829cbdfa9780b4564db9",
    "name": "python",
    "noarch": "generic",
    "python_site_packages_path": "lib/python3.99t/site-packages",
    "sha256": "a2be7c56f9ce3d6fc25220a49185894d02cf03b832bb9fb55122e6a662bde910",
    "size": 2912,
    "subdir": "noarch",
    "timestamp": 1726861043,
    "track_features": "",
    "url": "https://conda.anaconda.org/t/jj-80e459ed-f2bc-4975-ae2e-68f8e339b666/jjhelmus/label/sp_path/noarch/python-3.99.99-0.tar.bz2",
    "version": "3.99.99"
  }
]

[JohanMabille]

Hi, thanks for tackling this! The implementation is neat and looks good to me, can you add some test to check this is correctly working?

Also running pre-commit run --all-files should fix the linter.

[jjerphan]

Hi @jjhelmus, the support of CEP-17 is important for supporting Python 3.13t builds.

Are you still interested in continuing this PR?

[jjhelmus]

Hi @jjhelmus, the support of CEP-17 is important for supporting Python 3.13t builds.

Are you still interested in continuing this PR?

I can still work on this but progress will be slow. If anyone wants to take over this work that would be fine.

When I original started for on this, supported free-threading was a high priority for the team I was on. Since then, free-threading support is no longer a priority so I have very little time to work on this.

[jaimergp]

Hi! I'm reviewing conda/conda-libmamba-solver#628 and in there we are already assuming that python_site_packages_path will be the name of the attribute used in the libmambapy PackageRecord object. Can that be guaranteed even without this being merged yet? IOW, will you change the name of the attribute in this PR? Thanks!

[jjhelmus]

I found some time to work on this again and have been making some progress. Micromamba will now copy the contents of noarch: python packages into the location specified by the python_site_packages_path field when available in the package's repodata entry.

This can be checked using:

./build/micromamba/mamba create -p ./blah python=3.13 "python_abi=*=*_cp313t" imagesize -c conda-forge --yes
ls -d blah/lib/python3.13*

There should be a single directory, blah/lib/python3.13t and its site-packages subdirectory should contain the file from the imagesize package.

I'm still working on adding some tests, should have these complete by the end of the week.

[jjhelmus]

This PR is ready for review.

With these changes, noarch: python packages are installed into the location specific by the python_site_packages_path field of the python package when present. When not specified packages are into into the site-packages path determined from the version of the python package as is the existing behavior.

This field is exposed in libmambapy so that it can be used by conda-libmamba-solver and in turn conda.

There are tests at a unit and integration level.

Happy to address any concerns.