GitHub Action：如何在Job与Step的If条件中引用环境变量

我尝试在Job和Step级别的If条件中使用环境变量，但Job级的写法始终报错或不符合预期，Step级则正常。

我的初始代码：

name: CI/CD

on:
  push:
    branches: [ other, stable ]
env:
  BRANCH_NAME: ${{ github.head_ref || github.ref_name }}
  STABLE_BRANCH_NAME: stable
jobs:
  job1:
    name: test
    runs-on: [ self-hosted, linux, enterprise, .... ]
    container:
      image: some-image
    steps:
    - name: echo
      run: echo $BRANCH_NAME

在stable分支推送时，能正常打印stable。

尝试给Job添加If条件：

jobs:
  job1:
    name: test
    runs-on: [ self-hosted, linux, enterprise, .... ]
    container:
      image: some-image
    if: env.BRANCH_NAME == env.STABLE_BRANCH_NAME
    steps:
    - name: echo
      run: echo $BRANCH_NAME

执行失败，提示语法错误。改成if: ${{ env.BRANCH_NAME == env.STABLE_BRANCH_NAME }}后，依然无法正常工作。

我需要同时实现Job和Step级的If条件：

name: CI/CD

on:
  push:
    branches: [ other, stable ]
env:
  BRANCH_NAME: ${{ github.head_ref || github.ref_name }}
  STABLE_BRANCH_NAME: stable
jobs:
  job1:
    name: test
    runs-on: [ self-hosted, linux, enterprise, .... ]
    if: #### 这里需要判断分支是否为stable - 写法无效
    container:
      image: some-image
    steps:
    - name: echo
      run: echo $BRANCH_NAME
      if: ${{ env.STABLE_BRANCH_NAME != env.BRANCH_NAME }} # 这个写法正常工作

Step级的if: ${{ env.STABLE_BRANCH_NAME != env.BRANCH_NAME }}可以正常运行，但同样的写法在Job级别无效。有没有简便的解决方法？

解决方法 #

核心原因 #

GitHub Actions中，Job级别的全局env变量在Job的if条件判断阶段还未完成初始化，因此直接引用会失效；而Step级的env变量在Step执行前已初始化，所以可以正常使用。

简便实现方式 #

无需依赖自定义环境变量，直接在Job的if条件中使用GitHub上下文变量判断分支：

name: CI/CD

on:
  push:
    branches: [ other, stable ]
env:
  BRANCH_NAME: ${{ github.head_ref || github.ref_name }}
  STABLE_BRANCH_NAME: stable
jobs:
  job1:
    name: test
    runs-on: [ self-hosted, linux, enterprise, .... ]
    if: ${{ github.ref_name == 'stable' }} # 直接用上下文变量判断分支
    container:
      image: some-image
    steps:
    - name: echo
      run: echo $BRANCH_NAME
      if: ${{ env.STABLE_BRANCH_NAME != env.BRANCH_NAME }}

需复用环境变量的场景 #

如果需要在多个地方复用分支判断的变量，可以将环境变量定义在Job内部的env中，而非全局env，这样Job级的if就能正常引用：

name: CI/CD

on:
  push:
    branches: [ other, stable ]
jobs:
  job1:
    name: test
    runs-on: [ self-hosted, linux, enterprise, .... ]
    env:
      BRANCH_NAME: ${{ github.head_ref || github.ref_name }}
      STABLE_BRANCH_NAME: stable
    if: ${{ env.BRANCH_NAME == env.STABLE_BRANCH_NAME }}
    container:
      image: some-image
    steps:
    - name: echo
      run: echo $BRANCH_NAME
      if: ${{ env.STABLE_BRANCH_NAME != env.BRANCH_NAME }}

不过这种写法不如直接使用上下文变量简洁，推荐优先采用第一种方案。

内容的提问来源于stack exchange，提问作者Amin Ba