V1 conversion should use `python_min` instead of `python` in skip conditions for noarch Python recipes

[janjagusch]

Summary

When converting V0 recipes to V1 format for noarch: python packages, the selector conversion produces match(python, ...) expressions in skip conditions. However, per CFEP-25 standards, V1 noarch Python recipes only define python_min in their variant configuration—not python. This causes rattler-build to skip all variants because the python variable is undefined.

Current Behavior

Converting a V0 recipe with a Python version selector like [py<310] for a noarch Python package produces:

build:
  skip: match(python, "<3.10")
  noarch: python

Expected Behavior

For noarch: python recipes, the conversion should produce:

build:
  skip: match(python_min, "<3.10")
  noarch: python

Root Cause

The _upgrade_selectors_to_conditionals() method in recipe_parser_convert.py (lines 335-351) converts Python version selectors using hardcoded python variable:

bool_expression = Regex.SELECTOR_PYTHON_VERSION_REPLACEMENT.sub(
    r'match(python, "\1\2.\3")', bool_expression
)

The code does not check whether the recipe is a noarch: python package before deciding which variable to use.

Affected Patterns

V0 Selector	Current V1 Output	Expected V1 Output (noarch)
[py<310]	match(python, "<3.10")	match(python_min, "<3.10")
[py310]	match(python, "==3.10")	match(python_min, "==3.10")
[not py310]	match(python, "!=3.10")	match(python_min, "!=3.10")
[py2k]	match(python, ">=2,<3")	match(python_min, ">=2,<3")
[py3k]	match(python, ">=3,<4")	match(python_min, ">=3,<4")

Suggested Fix

In _upgrade_selectors_to_conditionals():

1. Check if the recipe has noarch: python in the build section
2. Use python_min instead of python in match expressions when noarch: python is detected

Related Issues

• Downstream issue in grayskull: skip: match(python, ...) should use python_min for v1 noarch recipes grayskull#644
• Downstream PR in cf-scripts: Fix dep_updates for v1 recipes using python_min conda-forge/conda-forge-bot#5306
• Related issues in this repo: Error converting a recipe with a set python_min variable #307, V1 recipe should contain ${{ python_min }}.* instead of ${{ python_min }} #308

Environment

• conda-recipe-manager version: latest (v0.9.3)

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This issue was generated with the assistance of Claude Code