Option to Set Default Package Type for pyproject.toml Dependencies (PyPI vs Conda)

[gitkief]

Pixi supports both the pyproject.toml and pixi.toml files for configuring Python projects. This flexibility is particularly useful if you want to fall back on Python's native tooling. When using the pyproject.toml, the listed dependencies are treated as PyPI dependencies by Pixi.

This behavior surprised me since Pixi describes itself as "Pixi is a fast software package manager built on top of the existing conda ecosystem." Given this description, I would have expected PyPI packages to serve as a fallback option rather than the primary one.

According to the documentation, the currently recommended approach to ensure Pixi installs conda dependencies instead is to explicitly list the dependencies in the [tool.pixi.dependencies] section again. For example:

[project]
name = "my_project"
requires-python = ">=3.9"
dependencies = [
    "numpy",
    "pandas",
    "matplotlib",
]

[tool.pixi.project]
channels = ["conda-forge"]
platforms = ["linux-64", "osx-arm64", "osx-64", "win-64"]

[tool.pixi.dependencies]
numpy = "*"
pandas = "*"
matplotlib = "*"

This approach may not be ideal for projects with a significant number of dependencies, as it introduces additional boilerplate. If this option doesn’t already exist (and apologies if I’ve overlooked it), I wonder if it might be a good idea to allow users to set a default package type or specify a rule such as, "handle all packages as conda dependencies except for the following ones...".