英文:
How do I actually generate an error using $PSCmdlet.WriteError in PowerShell?
问题
我一直在研究在PowerShell中生成错误消息的方法，并偶然发现了这个示例...
$Exception = [Exception]::new("错误消息")
$ErrorRecord = [System.Management.Automation.ErrorRecord]::new(
$Exception,
"错误ID",
[System.Management.Automation.ErrorCategory]::NotSpecified,
$TargetObject # 通常是触发错误的对象，如果可能的话
)
$PSCmdlet.WriteError($ErrorRecord)
然而，这不是一个有效的示例。我无法开始尝试它，因为我不知道如何使这个示例起作用。
InvalidOperation: 无法对空值表达式调用方法。
我知道我可以使用Write-Error来生成一个非终止错误，但我真的不希望错误消息回显我用来生成错误消息的命令。
英文:
I've been reading up on generating error messages in PowerShell and stumbled across this example...
$Exception = [Exception]::new("error message")
$ErrorRecord = [System.Management.Automation.ErrorRecord]::new(
$Exception,
"errorID",
[System.Management.Automation.ErrorCategory]::NotSpecified,
$TargetObject # usually the object that triggered the error, if possible
)
$PSCmdlet.WriteError($ErrorRecord)
However, this isn't a working example. I can't start experimenting with it, since I have no idea what would make the example tick to begin with.
InvalidOperation: You cannot call a method on a null-valued expression.
I do know I could use Write-Error instead to generate a non-terminating error. But I really don't like the error message to echo the command I used to generate the error message.
答案1
得分: 2
你的代码看起来不错，唯一的问题是，$PSCmdlet 只在 高级函数或脚本块 的上下文中可用：
function Testing {
[CmdletBinding()]
param($TargetObject)
$Exception = [Exception]::new('error message')
$ErrorRecord = [System.Management.Automation.ErrorRecord]::new(
$Exception,
'errorID',
[System.Management.Automation.ErrorCategory]::NotSpecified,
$TargetObject) # 通常是触发错误的对象，如果可能的话
$PSCmdlet.WriteError($ErrorRecord)
}
Testing foo!
针对评论的后续，再次强调，要在脚本块的上下文中（无论是 Invoke-Command 还是 Start-Job 或任何其他脚本块），它需要是高级脚本块，因此需要有 [CmdletBinding()] 或 [Parameter(...)] 修饰才能使用：
Start-Job {
[CmdletBinding()]
param($TargetObject)
$Exception = [Exception]::new('error message')
$ErrorRecord = [System.Management.Automation.ErrorRecord]::new(
$Exception,
'errorID',
[System.Management.Automation.ErrorCategory]::NotSpecified,
$TargetObject) # 通常是触发错误的对象，如果可能的话
$PSCmdlet.WriteError($ErrorRecord)
} -ArgumentList foo! | Receive-Job -AutoRemoveJob -Wait
$Error[0].TargetObject # foo!
英文:
Your code looks good, the only problem is that $PSCmdlet is only available for you in the context of an advanced function or script block:
function Testing {
[CmdletBinding()]
param($TargetObject)
$Exception = [Exception]::new('error message')
$ErrorRecord = [System.Management.Automation.ErrorRecord]::new(
$Exception,
'errorID',
[System.Management.Automation.ErrorCategory]::NotSpecified,
$TargetObject) # usually the object that triggered the error, if possible
$PSCmdlet.WriteError($ErrorRecord)
}
Testing foo!
Following up on comments, again, in the context of a script block (be it an Invoke-Command or Start-Job or any other script block) it would need to be an advanced one, so it would need to have a [cmdletbinding()] or [Parameter(...)] decoration for that to happen:
Start-Job {
[CmdletBinding()]
param($TargetObject)
$Exception = [Exception]::new('error message')
$ErrorRecord = [System.Management.Automation.ErrorRecord]::new(
$Exception,
'errorID',
[System.Management.Automation.ErrorCategory]::NotSpecified,
$TargetObject) # usually the object that triggered the error, if possible
$PSCmdlet.WriteError($ErrorRecord)
} -ArgumentList foo! | Receive-Job -AutoRemoveJob -Wait
$Error[0].TargetObject # foo!
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