name: Determine Rust toolchains
description: Determine Rust toolchains to test based on MSRV from Cargo.toml

outputs:
  toolchains:
    description: JSON array of Rust toolchains to test
    value: ${{ steps.toolchains.outputs.toolchains }}

runs:
  using: composite
  steps:
    - id: toolchains
      shell: bash
      run: |
        msrv="$(cargo metadata --format-version 1 --no-deps | jq -r '.packages[0].rust_version')"
        echo "toolchains=[\"$msrv\", \"stable\", \"nightly\"]" >> "$GITHUB_OUTPUT"