GitHub Actions能否在matrix定义中使用环境变量？

我在GitHub Action配置中编写了如下代码：

name: Build & Tests

on:
  pull_request:

env:
  CARGO_TERM_COLOR: always
  ZEROCOPY_MSRV: 1.61.0
  ZEROCOPY_CURRENT_STABLE: 1.64.0
  ZEROCOPY_CURRENT_NIGHTLY: nightly-2022-09-26

jobs:
  build_test:
    runs-on: ubuntu-latest

    strategy:
      matrix:
        # See `INTERNAL.md` for an explanation of these pinned toolchain
        # versions.
        channel: [ ${{ env.ZEROCOPY_MSRV }}, ${{ env.ZEROCOPY_CURRENT_STABLE }}, ${{ env.ZEROCOPY_CURRENT_NIGHTLY }} ]
        target: [ "i686-unknown-linux-gnu", "x86_64-unknown-linux-gnu", "arm-unknown-linux-gnueabi", "aarch64-unknown-linux-gnu", "powerpc-unknown-linux-gnu", "powerpc64-unknown-linux-gnu", "wasm32-wasi" ]
        features: [ "" , "alloc,simd", "alloc,simd,simd-nightly" ]
        exclude:
          # Exclude any combination which uses a non-nightly toolchain but
          # enables nightly features.
          - channel: ${{ env.ZEROCOPY_MSRV }}
            features: "alloc,simd,simd-nightly"
          - channel: ${{ env.ZEROCOPY_CURRENT_STABLE }}
            features: "alloc,simd,simd-nightly"

该文件出现如下解析错误：

Invalid workflow file: .github/workflows/ci.yml#L19
You have an error in your yaml syntax on line 19

错误指向的行（实际行号有偏差，可能是按零索引计数）为：

channel: [ ${{ env.ZEROCOPY_MSRV }}, ${{ env.ZEROCOPY_CURRENT_STABLE }}, ${{ env.ZEROCOPY_CURRENT_NIGHTLY }} ]

请问是否可以在matrix定义中这样使用变量？还是只能硬编码所有内容？

不能直接在matrix的数组定义里嵌入${{ env.XXX }}这类表达式，GitHub Actions的YAML解析器在处理matrix配置时不支持这种写法，会直接触发语法错误。

要实现变量复用，有两种可行方式：

方式一：硬编码+Job级Env复用 #

把版本号直接写在matrix中，同时在Job的env里定义变量，方便后续步骤复用：

name: Build & Tests

on:
  pull_request:

env:
  CARGO_TERM_COLOR: always

jobs:
  build_test:
    runs-on: ubuntu-latest
    env:
      ZEROCOPY_MSRV: 1.61.0
      ZEROCOPY_CURRENT_STABLE: 1.64.0
      ZEROCOPY_CURRENT_NIGHTLY: nightly-2022-09-26
    strategy:
      matrix:
        channel: [1.61.0, 1.64.0, nightly-2022-09-26]
        target: [ "i686-unknown-linux-gnu", "x86_64-unknown-linux-gnu", "arm-unknown-linux-gnueabi", "aarch64-unknown-linux-gnu", "powerpc-unknown-linux-gnu", "powerpc64-unknown-linux-gnu", "wasm32-wasi" ]
        features: [ "" , "alloc,simd", "alloc,simd,simd-nightly" ]
        exclude:
          - channel: 1.61.0
            features: "alloc,simd,simd-nightly"
          - channel: 1.64.0
            features: "alloc,simd,simd-nightly"

方式二：动态生成矩阵（复杂场景） #

如果需要更灵活的变量复用，比如从外部文件或API获取版本号，可以用actions/github-script在工作流运行时动态生成matrix。示例如下：

name: Build & Tests

on:
  pull_request:

env:
  CARGO_TERM_COLOR: always
  ZEROCOPY_MSRV: 1.61.0
  ZEROCOPY_CURRENT_STABLE: 1.64.0
  ZEROCOPY_CURRENT_NIGHTLY: nightly-2022-09-26

jobs:
  generate_matrix:
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.set_matrix.outputs.matrix }}
    steps:
      - id: set_matrix
        run: |
          echo "matrix={\"channel\": [\"${{ env.ZEROCOPY_MSRV }}\", \"${{ env.ZEROCOPY_CURRENT_STABLE }}\", \"${{ env.ZEROCOPY_CURRENT_NIGHTLY }}\"], \"target\": [\"i686-unknown-linux-gnu\", \"x86_64-unknown-linux-gnu\", \"arm-unknown-linux-gnueabi\", \"aarch64-unknown-linux-gnu\", \"powerpc-unknown-linux-gnu\", \"powerpc64-unknown-linux-gnu\", \"wasm32-wasi\"], \"features\": [\"\", \"alloc,simd\", \"alloc,simd,simd-nightly\"], \"exclude\": [{\"channel\": \"${{ env.ZEROCOPY_MSRV }}\", \"features\": \"alloc,simd,simd-nightly\"}, {\"channel\": \"${{ env.ZEROCOPY_CURRENT_STABLE }}\", \"features\": \"alloc,simd,simd-nightly\"}]}" >> $GITHUB_OUTPUT

  build_test:
    needs: generate_matrix
    runs-on: ubuntu-latest
    strategy:
      matrix: ${{ fromJson(needs.generate_matrix.outputs.matrix) }}
    steps:
      # 后续构建测试步骤
      - uses: actions/checkout@v4
      - run: cargo build --target ${{ matrix.target }} --features ${{ matrix.features }}

总结 #

• 直接在matrix数组中嵌入${{ env }}表达式不被支持，会触发YAML语法错误
• 简单场景推荐用硬编码+Job级Env的方式，兼顾可读性和复用性
• 复杂动态场景可以用动态生成矩阵的方法实现变量复用

内容的提问来源于stack exchange，提问作者joshlf