Question

在个人资料中，我通过prompt函数自定义了提示，以嵌入git分支信息：

function prompt
{
    $prefix = ""
    if ((test-path ".git") -or (test-path ".gitdir") -or ((git rev-parse --is-inside-work-tree 2> $null) -eq "true")) {
        $prefix = "[git:" + (& git symbolic-ref --short HEAD) + "]"
    }

    write-host "PS $prefix $(get-location) >" -nonewline -foregroundcolor DarkMagenta
    return " "
}

但是问题是，当我不在git树之外时，即使我将错误重定向到$ null，检查的git rev-parse部分也会在$error中插入错误。

这意味着$ error会因以下错误而受到污染，因为每次提示呈现时都会生成该错误：

git : fatal: Not a git repository (or any of the parent directories): .git
At C:\temp\prompt.ps1:4 char:64
    + ... ".gitdir") -or ((git rev-parse --is-inside-work-tree 2> $null) -eq "t ...
    +                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (fatal: Not a gi...ectories): .git:String) [], RemoteException
    + FullyQualifiedErrorId : NativeCommandError

以交互方式运行时，我注意到2> $null确实抑制了控制台的错误，但是该错误仍然显示在$ error中：

PS C:\temp> $error
PS C:\temp> git rev-parse --is-inside-work-tree 2> $null
PS C:\temp> $error
git : fatal: Not a git repository (or any of the parent directories): .git
At line:1 char:1
+ git rev-parse --is-inside-work-tree 2> $null
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (fatal: Not a gi...ectories): .git:String) [], RemoteException
    + FullyQualifiedErrorId : NativeCommandError

PS C:\temp>

我尝试将命令包装在try {...} catch {}中，并且还使用了invoke-command，并且忽略了错误操作，但都没有运气：

PS c:\temp> $error.clear()
PS c:\temp> $error
PS c:\temp> invoke-command -scriptblock { git rev-parse --is-inside-work-tree 2> $null } -erroraction ignore
PS c:\temp> $error
git : fatal: Not a git repository (or any of the parent directories): .git
At line:1 char:31
+ ... d -scriptblock { git rev-parse --is-inside-work-tree 2> $null } -erro ...
+                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (fatal: Not a gi...ectories): .git:String) [], RemoteException
    + FullyQualifiedErrorId : NativeCommandError

PS c:\temp> $error.clear()
PS c:\temp> $error
PS c:\temp> try { git rev-parse --is-inside-work-tree 2> $null } catch { }
PS c:\temp> $error
git : fatal: Not a git repository (or any of the parent directories): .git
At line:1 char:7
+ try { git rev-parse --is-inside-work-tree 2> $null } catch { }
+       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (fatal: Not a gi...ectories): .git:String) [], RemoteException
    + FullyQualifiedErrorId : NativeCommandError

PS c:\temp>

如何抑制此错误添加到$error中，使其保持干净？

Answer 1

Unfortunately, as of PowerShell Core 6.2.1 / Windows PowerShell v5.1, using 2>$null to suppress stderr output from an external program unexpectedly still takes a detour via Powershell's error stream (stream 2), so the output is still recorded in $Error. This known problem is described in this GitHub issue.

As a workaround, you can call git via cmd /c (or sh -c on Unix) and let it do the redirection:

# Windows
cmd /c 'git rev-parse --is-inside-work-tree 2>NUL'

# Linux, macOS
sh -c 'git rev-parse --is-inside-work-tree 2>/dev/null'

As you state, this will correctly pass git's exit code through so you can determine success via $LASTEXITCODE afterwards.

禁止从Powershell $ error输出外部命令错误

1 个答案: