在GitHub Actions的windows-latest环境中无法生成Step Summary

问题原因 #

Windows环境的GitHub Actions默认用PowerShell执行脚本，而PowerShell里引用环境变量的语法是$env:变量名，你之前直接写$GITHUB_STEP_SUMMARY会被PowerShell识别为本地变量，而非系统环境变量，所以才会出现取值为空的错误。

解决方案1：使用PowerShell正确的环境变量语法 #

把脚本里的$GITHUB_STEP_SUMMARY替换成$env:GITHUB_STEP_SUMMARY即可：

name: Testing windows summaries

on:
  pull_request:
    branches: [master]
    types: [synchronize, opened, reopened, ready_for_review]

jobs:
  build-and-test:
    name: Test
    runs-on: "windows-latest"
    steps:
    - name: Adding markdown
      run: |
       echo '### Hello world! ' >> $env:GITHUB_STEP_SUMMARY
       cat $env:GITHUB_STEP_SUMMARY

解决方案2：切换到Cmd执行脚本 #

如果更习惯Cmd的语法，可以指定Step使用shell: cmd，环境变量改用%变量名%的格式：

name: Testing windows summaries

on:
  pull_request:
    branches: [master]
    types: [synchronize, opened, reopened, ready_for_review]

jobs:
  build-and-test:
    name: Test
    runs-on: "windows-latest"
    steps:
    - name: Adding markdown (using cmd)
      shell: cmd
      run: |
       echo '### Hello world! ' >> %GITHUB_STEP_SUMMARY%
       type %GITHUB_STEP_SUMMARY%

内容的提问来源于stack exchange，提问作者Heberto Mayorquin