PowerShell 中有没有办法获取脚本参数的默认值?

问题描述

要使用 Start-Job 启动脚本，需要在提供给 -ArgumentList 的数组中使用正确的参数顺序.

For launching scripts with Start-Job it is required to use the correct order of parameters within the array provided to -ArgumentList.

考虑这个脚本:

# $script = c:\myScripts.ps1
Param (
    [Parameter(Mandatory)]
    [String]$ScriptName,
    [Parameter(Mandatory)]
    [String]$Path,
    [Parameter(Mandatory)]
    [String[]]$MailTo,
    [String]$LogFolder = "\\$env:COMPUTERNAME\Log",
    [String]$ScriptAdmin = '[email protected]'
)

我们想知道如何检索 $LogFolder 和 $ScriptAdmin 中设置的默认值?

We would like to know how it is possible to retrieve the default values set in $LogFolder and $ScriptAdmin?

我似乎无法找到它的尝试:

My attempt where I can't seem to find it:

  $scriptParameters = (Get-Command $script).Parameters.GetEnumerator() |
    Where-Object { $psBuildInParameters -notContains $_.Key }

    foreach ($p in $scriptParameters.GetEnumerator()) {
        'Name: {0} Type: {1} Mandatory: {2} DefaultValue: x' -f $p.Value.Name, $p.Value.ParameterType, $p.Value.Attributes.Mandatory
    }

如果我们有默认值，我们可以更灵活地使用 Start-Job，以防我们只想使用强制参数启动作业并说 $ScriptAdmini，但是想要将值保留在 $LogFolder 中，而不是用空字符串将其清空，因为我们需要尊重顺序或参数.

If we have the default value we can use Start-Job more flexible in case we want to start a job with only the mandatory parameters and say $ScriptAdmini, but want to keep the value in $LogFolder and not blank it out with an empty string because we need to respect the order or the arguments.

推荐答案

您可以为此使用 Ast 解析:

You can use Ast parsing for this:

$script = 'c:\myScripts.ps1'

# Parse the script file for objects based on Ast type
$parsed = [System.Management.Automation.Language.Parser]::ParseFile($script,[ref]$null,[ref]$null)

# Extract only parameter ast objects
$params = $parsed.FindAll({$args[0] -is [System.Management.Automation.Language.ParameterAst]},$true)

$params | Foreach-Object {
    $name = $_.Name.VariablePath.ToString()
    $type = $_.StaticType.FullName
    # Convoluted because the property values themselves present strings rather than booleans where the values are $false or false
    $mandatory = [bool]($_.Attributes | where {$_.NamedArguments.ArgumentName -eq 'Mandatory'} |% {$_.NamedArguments.Argument.SafeGetValue()})
    $DefaultValue = $_.DefaultValue.Value
    "Name: {0} Type: {1} Mandatory: {2} DefaultValue: {3}" -f $name,$type,$mandatory,$DefaultValue
}

参见 System.Management.Automation.Language Namespace 用于其他潜在的抽象语法树类型.

See System.Management.Automation.Language Namespace for other potential abstract syntax tree types.

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