GitHub Action工作流中PowerShell命令执行失败问题求助

问题场景 #

构建自定义GitHub Action时，执行以下PowerShell命令出现语法错误：

powershell -NoLogo -Sta -NoProfile -NonInteractive -ExecutionPolicy Unrestricted -Command "$VerbosePreference = 'SilentlyContinue' ; Get-ChildItem -LiteralPath '%~dp0' | ForEach-Object { Write-Verbose ('Unblock: {0}' -f $_.FullName) ; $_ } | Unblock-File | Out-Null"

报错信息：

At line:1 char:127
+ ... h '%~dp0' | ForEach-Object { Write-Verbose ('Unblock: {0}' -f .FullNa ...
+                                                                  ~
You must provide a value expression following the '-f' operator.
At line:1 char:128
+ ... | ForEach-Object { Write-Verbose ('Unblock: {0}' -f .FullName) ;  } | ...
+                                                         ~~~~~~~~~
Unexpected token '.FullName' in expression or statement.
At line:1 char:127
+ ... h '%~dp0' | ForEach-Object { Write-Verbose ('Unblock: {0}' -f .FullNa ...
+                                                                  ~
Missing closing ')' in expression.
At line:1 char:93
+ ... inue' ; Get-ChildItem -LiteralPath '%~dp0' | ForEach-Object { Write-V ...
+                                                                 ~
Missing closing '}' in statement block or type definition.
At line:1 char:137
+ ...  ForEach-Object { Write-Verbose ('Unblock: {0}' -f .FullName) ;  } |  ...
+                                                                 ~
Unexpected token ')' in expression or statement.
At line:1 char:142
+ ... ach-Object { Write-Verbose ('Unblock: {0}' -f .FullName) ;  } | Unblo ...
+                                                                 ~
Unexpected token '}' in expression or statement.
At line:1 char:144
+ ... h-Object { Write-Verbose ('Unblock: {0}' -f .FullName) ;  } | Unblock ...
+                                                                 ~
An empty pipe element is not allowed.
    + CategoryInfo          : ParserError: (:) [], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : ExpectedValueExpression

原因分析 #

1. YAML环境的$符号解析问题：GitHub Action的YAML配置会自动解析$开头的变量，原命令中的$_和$VerbosePreference里的$被YAML解析器处理后丢失，导致PowerShell收到的命令中变成.FullName和VerbosePreference，直接引发语法错误。
2. 路径变量语法不兼容：%~dp0是CMD脚本的专用变量，用于获取当前脚本所在目录，但在GitHub Action直接调用PowerShell的场景下，这个变量无法被PowerShell识别，会被当作字面量路径处理，大概率找不到对应目录。

修复方案 #

方案1：转义$符号并替换路径变量 #

将命令中的所有$替换为$$（YAML中用于转义$的写法），同时把%~dp0替换为GitHub Action的内置变量${{ github.action_path }}（自定义Action的脚本目录）或$PWD.Path（当前工作目录）：

powershell -NoLogo -Sta -NoProfile -NonInteractive -ExecutionPolicy Unrestricted -Command "$$VerbosePreference = 'SilentlyContinue' ; Get-ChildItem -LiteralPath '${{ github.action_path }}' | ForEach-Object { Write-Verbose ('Unblock: {0}' -f $$_.FullName) ; $$_ } | Unblock-File | Out-Null"

方案2：改用多行PowerShell脚本写法 #

在GitHub Action中直接指定shell: powershell，用多行脚本的方式避免引号和转义问题，可读性更强：

- name: Unblock Action Files
  shell: powershell
  run: |
    $VerbosePreference = 'SilentlyContinue'
    Get-ChildItem -LiteralPath "${{ github.action_path }}" | ForEach-Object {
        Write-Verbose ("Unblock: {0}" -f $_.FullName)
        $_
    } | Unblock-File | Out-Null

内容的提问来源于stack exchange，提问作者Nesan Mano