core/.github/actions/setup-uv-python/action.yml

name: Set up uv and managed Python
description: >-
  Pins uv (avoids the raw.githubusercontent.com manifest fetch on cache miss)
  and proactively installs the requested Python so cached venvs created with
  `uv venv` resolve their interpreter symlinks in jobs that only restore the
  venv. setup-uv alone only sets UV_PYTHON, it does not actually fetch the
  interpreter until uv first uses it, so jobs that just activate the venv
  blow up with broken symlinks on cache hit.

inputs:
  python-version:
    description: The Python version uv should install and use.
    required: true
  uv-version:
    description: The uv version setup-uv should install.
    required: true

outputs:
  python-version:
    description: The Python version uv reports as installed.
    value: ${{ steps.uv.outputs.python-version }}

runs:
  using: composite
  steps:
    - name: Set up uv
      id: uv
      uses: astral-sh/setup-uv@fac544c07dec837d0ccb6301d7b5580bf5edae39 # v8.2.0
      with:
        version: ${{ inputs.uv-version }}
        python-version: ${{ inputs.python-version }}
        # Persist astral's managed Python across jobs so 'uv venv' below is
        # fast on the second job onwards.
        cache-python: true
        # Lint-only and codegen jobs touch no Python deps, so the post-step
        # cache save would otherwise abort the job.
        ignore-nothing-to-cache: true
    # setup-uv only sets UV_PYTHON; it does not fetch the interpreter until uv
    # first uses it. Jobs that only restore and activate a cached venv never
    # trigger that lazy install, so without this step they hit broken
    # interpreter symlinks on a cache hit.
    - name: Install Python interpreter
      shell: bash
      env:
        PYTHON_VERSION: ${{ inputs.python-version }}
      run: uv python install "${PYTHON_VERSION}"