powershell - Set-PSDebug -Trace 2导致我的powershell代码抛出了一个错误，如果不进行跟踪就不会发生

Question

想象一个脚本test.ps1，如下所示:

Param (
    [ValidateNotNullOrEmpty()]
    $VMHost,

    [switch]
    $trace
)

$ErrorActionPreference = "Stop"
Set-StrictMode -Version 2

trap {
    Set-PSDebug -Trace 0
    $_.InvocationInfo
    break
}

if ($trace) {
    Set-PSDebug -Trace 2
}

if ($VMHost) {
    $VMHost = @(@($VMHost) | % {
        $h = $_
        Switch ($h.GetType().Name) {
            'String' {
                "isastring"
            }
            default {
                Write-Error -Category InvalidType -TargetObject $h -ErrorAction Stop -Message 'VMHost argument must be a String or a VMHost object.'
            }
        }
    })
}

正常运行时，它会执行以下操作:

PS> & .\test.ps1 -VMHost "foo"
foo

当使用 -trace参数运行时，它将执行以下操作:

PS> & .\test.ps1 -VMHost "foo" -trace
DEBUG:   21+ if ( >>>> $VMHost) {
DEBUG:   22+      >>>> $VMHost = @(@($VMHost) | % {
DEBUG:   22+     $VMHost = @( >>>> @($VMHost) | % {
DEBUG:   22+     $VMHost = @(@( >>>> $VMHost) | % {
DEBUG:   22+     $VMHost = @(@($VMHost) | %  >>>> {
DEBUG:     ! CALL function '<ScriptBlock>'  (defined in file 'path...\test.ps1')
DEBUG:   23+          >>>> $h = $_
DEBUG:     ! SET $h = 'foo'.
DEBUG:     ! SET $switch = 'String'.
DEBUG:   24+         Switch ( >>>> $h.GetType().Name) {
DEBUG:     ! SET $switch = ''.
DEBUG:   35+      >>>> })
DEBUG:     ! SET $VMHost = ''.
DEBUG:   13+      >>>> Set-PSDebug -Trace 0
DEBUG:     ! CALL function '<ScriptBlock><trap>'  (defined in file
'path...\test.ps1')


MyCommand             :
BoundParameters       : {}
UnboundArguments      : {}
ScriptLineNumber      : 23
OffsetInLine          : 19
HistoryId             : -1
ScriptName            : path...\test.ps1
Line                  :     $VMHost = @(@($VMHost) | % {

PositionMessage       : At path...\test.ps1:23 char:19
                        +     $VMHost = @(@($VMHost) | % {
                        +                   ~~~~~~~
PSScriptRoot          : C:\Users\ereisner\TenableAppliancePackaging
PSCommandPath         : C:\Users\ereisner\TenableAppliancePackaging\test.ps1
InvocationName        :
PipelineLength        : 0
PipelinePosition      : 0
ExpectingInput        : False
CommandOrigin         : Internal
DisplayScriptPosition :

The variable cannot be validated because the value System.Object[] is not a valid value for the VMHost variable.
At path...\test.ps1:22 char:19
+     $VMHost = @(@($VMHost) | % {
+                   ~~~~~~~
    + CategoryInfo          : MetadataError: (:) [], ParentContainsErrorRecordException
    + FullyQualifiedErrorId : ValidateSetFailure

跟踪调试如何导致这样的错误？

powershell在这里做什么？

可以清楚地重写此过滤器/分配以避免此问题(错误吗？)？

Powershell版本信息:

PS> $PSVersionTable
Name                           Value
----                           -----
PSVersion                      3.0
WSManStackVersion              3.0
SerializationVersion           1.1.0.1
CLRVersion                     4.0.30319.42000
BuildVersion                   6.2.9200.16481
PSCompatibleVersions           {1.0, 2.0, 3.0}
PSRemotingProtocolVersion      2.2

Answer 1

没有完整的答案，但看来这是Powershell版本3的错误。

问题似乎在于在这种情况下switch的行为方式。它似乎在给定的单个字符串参数的末尾“循环”了一个。

在PS 4下运行的相同代码按预期工作。