ci.yml

name: CI

on:
  push:
    branches: [main]
  pull_request:

env:
  CARGO_TERM_COLOR: always

jobs:
  ci:
    name: test / fmt / clippy
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Install Rust toolchain
        uses: dtolnay/rust-toolchain@stable
        with:
          components: rustfmt, clippy

      - name: Cache cargo build artifacts
        uses: Swatinem/rust-cache@v2

      - name: Check formatting
        run: cargo fmt --check

      - name: Run clippy
        run: cargo clippy --all-targets -- -D warnings

      - name: Run tests
        run: cargo test

  # Cargo.toml 声明 rust-version = "1.86"，CONTRIBUTING.md 把它写成对贡献者的契约，而上面的
  # job 只装最新 stable —— 声明因此没有任何执行者：clippy 的修复建议会推着代码越过这条线
  # （例如 unsigned_is_multiple_of 是 1.87 才稳定的 API），在 stable 上仍然是全绿。
  # 本 job 只装「被声明的那一版」，让该契约第一次变成一道会红的门禁。
  msrv:
    name: msrv (the version Cargo.toml declares)
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Install the declared MSRV toolchain
        uses: dtolnay/rust-toolchain@1.86

      # 声明一旦抬高，这里必须同步：否则本 job 测着旧版本、而 Cargo.toml 已经声明新高，
      # 等于又退回「声明没有执行者」。这一步把两者钉在一起。
      - name: Assert the installed toolchain is the declared rust-version
        run: |
          declared=$(grep -m1 '^rust-version' Cargo.toml | cut -d'"' -f2)
          installed=$(rustc --version | cut -d' ' -f2)
          echo "Cargo.toml rust-version = ${declared}; installed rustc = ${installed}"
          case "$installed" in
            "$declared"|"$declared".*) ;;
            *)
              echo "::error::Cargo.toml declares rust-version \"${declared}\" but this job installs rustc ${installed} — bump the toolchain in .github/workflows/ci.yml"
              exit 1
              ;;
          esac

      - name: Cache cargo build artifacts
        uses: Swatinem/rust-cache@v2

      # --locked：钉住仓库里那份 Cargo.lock —— 否则 lockfile 与 Cargo.toml 一旦不一致，
      # runner 会就地重新解析、构建照样通过，而提交进仓库的那份 lockfile 仍是坏的。
      - name: Build with the declared MSRV
        run: cargo build --locked