python version dependent package versions in noarch builds

[zerothi]

Conda-forge documentation

• I could not solve my problem using the conda-forge documentation.

Installed packages

I am using the feedstock to build the binaries.

Environment info

N/A

Issue

I am trying to construct a package with different package dependencies depending on the installed python version.

So a recipe.yaml (rattler-build) looking like this:

build:
  noarch: python
requirements:
  host:
    - python ${{ python_min }}.*
    - pip
    - setuptools_scm >=6.2
    - pyproject-metadata
  run:
    - python >=${{ python_min }},<=${{ python_max }}
    - if: match(python, "==3.9")
      then: sympy_plot_backends >=3.1.1,<3.3
      else: sympy_plot_backends >=3.4,<4
tests:
  python:
    python_version:
      - "3.9"
      - "3.12"

I know, this is bad practice, I am not the package maintainer, only release maintainer.

FYI, I can get this working if the recipes are build per python version, however, it is a pure python package, and so I wanted to return to a noarch build. This might be the problem...

I would suspect that the above incorporates in the conda-package the logic that says:

When I install a python 3.9 version, I get sympy_plot_backends >=3.1.1,<3.3.
When I install a python >3.9 version, I get sympy_plot_backends >=3.4,<4.

However, my suspicion is that the noarch build and it being built at python_min version means that the package only keeps the 3.9 package requirements and thus does not uphold the other requirement?

At least this is what is reflected in the CI:

│ Finalized run dependencies (dtumathtools-2025.2.0-pyhc364b38_3):
 │ ╭─────────────────────┬────────────────────────╮
 │ │ Name                ┆ Spec                   │
 │ ╞═════════════════════╪════════════════════════╡
 │ │ Run dependencies    ┆                        │
 │ │ jupyter             ┆ >=1.0.0                │
 │ │ matplotlib          ┆ >=3.8,<3.10            │
 │ │ numpy               ┆ >=1.24,<2              │
 │ │ python              ┆ >=3.9,<=3.12           │
 │ │                     ┆ (RE of [host: python]) │
 │ │ sympy               ┆ ~=1.12                 │
 │ │ sympy_plot_backends ┆ >=3.1.1,<3.3           │
 │ │                     ┆                        │
 │ │ Run constraints     ┆                        │
 │ │ colorcet            ┆ *                      │
 │ │ ipyevents           ┆ *                      │
 │ │ ipympl              ┆ >=0.7.0                │
 │ │ ipywidgets_bokeh    ┆ *                      │
 │ │ k3d                 ┆ >=2.9.7                │
 │ │ mayavi              ┆ ~=4.8,>=4.8.2          │
 │ │ panel               ┆ >=1.0.0                │
 │ │ plotly              ┆ >=4.14.3               │
 │ │ pyqt                ┆ ~=5.15.9               │
 │ │ vtk                 ┆ *                      │
 │ ╰─────────────────────┴────────────────────────╯

In the test-build I get:

...
 │ │ │ │ python                        ┆ 3.12.0       ┆ hab00c5b_0_cpython   ┆ conda-forge ┆   30.64 MiB │
...
 │ │ │ │ sympy_plot_backends           ┆ 3.2.0        ┆ pyhd8ed1ab_0         ┆ conda-forge ┆  208.63 KiB │
...

which clearly shows this behavior.

I would say this is my problem, but it's still a bit problematic that conda eats the recipe without problems since it shows a problem in the dependency detection.

[hmaarrfk]

You can’t do this with noarch in a straight forward way.

I take it you really need 3.9.

Just build one last version for 3.9 then move on to newer pythons

[zerothi]

Yeah, that was my take home, my point here is that when specifying noarch there can't be any matches(python, *) checks, that seems like it isn't built into the package...