powershell - Powershell scriptblock变量作用域和模块的奇怪行为，有什么建议吗？

注意:我在Windows Vista上使用PowerShell 2.0。

我试图增加对为psake指定构建参数的支持，但是我遇到了一些奇怪的PowerShell变量作用域行为，专门用于处理使用Export-ModuleMember导出的调用函数(这是psake公开它的主要方法)。以下是一个简单的PowerShell模块进行说明(名为repoCase.psm1):

function Test {
    param(
        [Parameter(Position=0,Mandatory=0)]
        [scriptblock]$properties = {}
    )

    $defaults = {$message = "Hello, world!"}

    Write-Host "Before running defaults, message is: $message"

    . $defaults

    #At this point, $message is correctly set to "Hellow, world!"
    Write-Host "Aftering running defaults, message is: $message"

    . $properties

    #At this point, I would expect $message to be set to whatever is passed in,
    #which in this case is "Hello from poperties!", but it isn't.
    Write-Host "Aftering running properties, message is: $message"
}

Export-ModuleMember -Function "Test"

要测试该模块，请运行以下命令序列(确保您与repoCase.psm1位于同一目录中):

Import-Module .\repoCase.psm1

#Note that $message should be null
Write-Host "Before execution - In global scope, message is: $message"

Test -properties { "Executing properties, message is $message"; $message = "Hello from properties!"; }

#Now $message is set to the value from the script block.  The script block affected only the global scope.
Write-Host "After execution - In global scope, message is: $message"

Remove-Module repoCase

我预期的行为是因为我传递给Test的脚本块会影响Test的本地范围。它是“点源”的，因此所做的任何更改都应在调用者的范围之内。但是，这不是正在发生的事情，它似乎正在影响声明它的范围。这是输出:

Before execution - In global scope, message is:
Before running defaults, message is:
Aftering running defaults, message is: Hello, world!
Executing properties, message is
Aftering running properties, message is: Hello, world!
After execution - In global scope, message is: Hello from properties!

有趣的是，如果我不将Test导出为模块，而是声明函数并调用它，那么一切都会像我期望的那样工作。脚本块仅影响Test的范围，而不会修改全局范围。

我不是PowerShell专家，但是有人可以向我解释此行为吗？

最佳答案

我一直在研究这个问题，这个问题出现在我正在研究的项目中，发现了三件事:

该问题特定于模块。

如果调用scriptBlock的代码实际上位于.psm1文件内的任何位置，我们将看到此行为。

如果从模块传入了scriptBlock，则调用scriptBlock的代码位于单独的脚本文件(.ps1)中时，也会看到该行为。

如果未从模块传递scriptBlock，则如果调用scriptBlock的代码位于脚本文件(.ps1)中的任何位置，则看不到此行为。

scriptBlock不一定在全局范围内执行。相反，它似乎总是在调用模块函数的任何范围内执行。

问题不仅限于“。”运算子(dotsource)。我已经测试了三种不同的方式来调用scriptBlock:“”。运算符，“＆”运算符以及scriptBlock对象的invoke()方法。在后两种情况下，scriptBlock在错误的父范围内执行。可以通过尝试调用{set-variable -name "message" -scope 1 -value "From scriptBlock"}

进行调查

我希望这能为问题提供更多的启示，尽管我还没有提出足够的建议。

是否还有人安装了PowerShell 1？如果是这样，则可以检查它是否显示相同的行为，这将很有用。

这是我的测试用例的文件。要运行它们，请在同一目录中创建所有四个文件，然后在PowerShell ISE命令行中执行“./all_tests.ps1”

script_toplevel.ps1

param($script_block)

set-alias "wh" write-host

$message = "Script message"
wh "  Script message before:      '$message'"
. $script_block
wh "  Script message after:       '$message'"

script_infunction.ps1

param($script_block)
set-alias "wh" write-host

function f {
    param($script_block)
    $message = "Function message"
    wh "  Function message before:    '$message'"
    . $script_block
    wh "  Function message after:     '$message'"
}

$message = "Script message"
wh "  Script message before:      '$message'"
f -script_block $script_block
wh "  Script message after:       '$message'"

module.psm1

set-alias "wh" write-host

function simple_test_fun {
    param($script_block)

    $message = "ModFunction message"
    wh "  ModFunction message before: '$message'"
    . $script_block
    wh "  ModFunction message after:  '$message'"
}

function ampersand_test_fun {
    param($script_block)

    $message = "ModFunction message"
    wh "  ModFunction message before: '$message'"
    & $script_block
    wh "  ModFunction message after:  '$message'"
}

function method_test_fun {
    param($script_block)

    $message = "ModFunction message"
    wh "  ModFunction message before: '$message'"
    $script_block.invoke()
    wh "  ModFunction message after:  '$message'"
}

function test_mod_to_script_toplevel {
    param($script_block)

    $message = "ModFunction message"
    wh "  ModFunction message before: '$message'"
    & .\script_toplevel.ps1 -script_block $script_block
    wh "  ModFunction message after:  '$message'"
}

function test_mod_to_script_function {
    param($script_block)

    $message = "ModFunction message"
    wh "  ModFunction message before: '$message'"
    & .\script_infunction.ps1 -script_block $script_block
    wh "  ModFunction message after:  '$message'"
}

export-modulemember -function "simple_test_fun", "test_mod_to_script_toplevel", "test_mod_to_script_function", "ampersand_test_fun", "method_test_fun"

all_tests.ps1

remove-module module
import-module .\module.psm1

set-alias "wh" write-host

wh "Test 1:"
wh "  No problem with . at script top level"
wh "    ScriptBlock created at 'TopScript' scope"
wh "    TopScript -amp-calls-> Script -dot-calls-> ScriptBlock:"
wh
wh "  Expected behavior: Script message after:       'Script block message'"
wh "  Problem behavior:  TopScript message after:    'Script block message'"
wh
wh "Results:"

$global:message = "Global message"
$message = "Top script message"
wh "  Global message before:      '$global:message'"
wh "  TopScript message before:   '$message'"
& .\script_toplevel.ps1 -script_block {$message = "Script block message"}
wh "  TopScript message after:    '$message'"
wh "  Global message after:       '$global:message'"

wh
wh "Test 1 showed expected behavior"
wh
wh
wh "Test 2:"
wh "  No problem with . inside function in script"
wh "    ScriptBlock created at 'TopScript' scope"
wh "    TopScript -amp-calls-> Script -calls-> Function -dot-calls-> ScriptBlock:"
wh
wh "  Expected behavior: Function message after:     'Script block message'"
wh "  Problem behavior:  TopScript message after:    'Script block message'"
wh
wh "Results:"
$global:message = "Global message"
$message = "Top script message"
wh "  Global message before:      '$global:message'"
wh "  TopScript message before:   '$message'"
& .\script_infunction.ps1 -script_block {$message = "Script block message"}
wh "  TopScript message after:    '$message'"
wh "  Global message after:       '$global:message'"

wh
wh "Test 2 showed expected behavior"
wh
wh
wh "Test 3:"
wh "  Problem with with . with function in module"
wh "    ScriptBlock created at 'TopScript' scope"
wh "    TopScript -calls-> ModFunction -dot-calls-> ScriptBlock:"
wh
wh "  Expected behavior: ModFunction message after:  'Script block message'"
wh "  Problem behavior:  TopScript message after:    'Script block message'"
wh
wh "Results:"
$global:message = "Global message"
$message = "Top script message"
wh "  Global message before:      '$global:message'"
wh "  TopScript message before:   '$message'"
simple_test_fun -script_block {$message = "Script block message"}
wh "  TopScript message after:    '$message'"
wh "  Global message after:       '$global:message'"

wh
wh "Test 3 showed problem behavior"
wh
wh
wh "Test 4:"
wh "  Confirm that problem scope is always scope where ScriptBlock is created"
wh "    ScriptBlock created at 'f1' scope"
wh "    TopScript -calls-> f1 -calls-> f2 -amp-calls-> ModFunction -dot-calls-> ScriptBlock:"
wh
wh "  Expected behavior: ModFunction message after:  'Script block message'"
wh "  Problem behavior:  f1 message after:           'Script block message'"
wh
wh "Results:"
$global:message = "Global message"
$message = "Top script message"
wh "  Global message before:      '$global:message'"
wh "  TopScript message before:   '$message'"
function f1 {
    $message = "f1 message"
    wh "  f1 message before:          '$message'"
    f2 -script_block {$message = "Script block message"}
    wh "  f1 message after:           '$message'"
}
function f2 {
    param($script_block)

    $message = "f2 message"
    wh "  f2 message before:          '$message'"
    simple_test_fun -script_block $script_block
    wh "  f2 message after:           '$message'"
}

f1
wh "  TopScript message after:    '$message'"
wh "  Global message after:       '$global:message'"

wh
wh "Test 4 showed problem behavior"
wh
wh
wh "Test 4:"
wh "  Confirm that problem scope is always scope where ScriptBlock is created"
wh "    ScriptBlock created at 'f1' scope"
wh "    TopScript -calls-> f1 -calls-> f2 -amp-calls-> ModFunction -dot-calls-> ScriptBlock:"
wh
wh "  Expected behavior: ModFunction message after:  'Script block message'"
wh "  Problem behavior:  f1 message after:           'Script block message'"
wh
wh "Results:"
$global:message = "Global message"
$message = "Top script message"
wh "  Global message before:      '$global:message'"
wh "  TopScript message before:   '$message'"
function f1 {
    $message = "f1 message"
    wh "  f1 message before:          '$message'"
    f2 -script_block {$message = "Script block message"}
    wh "  f1 message after:           '$message'"
}
function f2 {
    param($script_block)

    $message = "f2 message"
    wh "  f2 message before:          '$message'"
    simple_test_fun -script_block $script_block
    wh "  f2 message after:           '$message'"
}

f1
wh "  TopScript message after:    '$message'"
wh "  Global message after:       '$global:message'"

wh
wh "Test 4 showed problem behavior"
wh
wh
wh "Test 5:"
wh "  Problem with with . when module function invokes script (toplevel)"
wh "    ScriptBlock created at 'TopScript' scope"
wh "    TopScript -calls-> ModFunction -amp-calls-> Script -dot-calls-> ScriptBlock:"
wh
wh "  Expected behavior: ModFunction message after:  'Script block message'"
wh "  Problem behavior:  TopScript message after:    'Script block message'"
wh
wh "Results:"
$global:message = "Global message"
$message = "Top script message"
wh "  Global message before:      '$global:message'"
wh "  TopScript message before:   '$message'"
test_mod_to_script_toplevel -script_block {$message = "Script block message"}
wh "  TopScript message after:    '$message'"
wh "  Global message after:       '$global:message'"

wh
wh "Test 5 showed problem behavior"
wh
wh
wh "Test 6:"
wh "  Problem with with . when module function invokes script (function)"
wh "    ScriptBlock created at 'TopScript' scope"
wh "    TopScript -calls-> ModFunction -amp-calls-> Script -calls-> function -dot-calls-> ScriptBlock:"
wh
wh "  Expected behavior: ModFunction message after:  'Script block message'"
wh "  Problem behavior:  TopScript message after:    'Script block message'"
wh
wh "Results:"
$global:message = "Global message"
$message = "Top script message"
wh "  Global message before:      '$global:message'"
wh "  TopScript message before:   '$message'"
test_mod_to_script_function -script_block {$message = "Script block message"}
wh "  TopScript message after:    '$message'"
wh "  Global message after:       '$global:message'"

wh
wh "Test 6 showed problem behavior"
wh
wh
wh "Test 7:"
wh "  Problem with with & with function in module"
wh "    ScriptBlock created at 'TopScript' scope"
wh "    TopScript -calls-> ModFunction -amp-calls-> Script -calls-> function -dot-calls-> ScriptBlock:"
wh
wh "  Expected behavior: ModFunction message after:  'Script block message'"
wh "  Problem behavior:  TopScript message after:    'Script block message'"
wh
wh "Results:"
$global:message = "Global message"
$message = "Top script message"
wh "  Global message before:      '$global:message'"
wh "  TopScript message before:   '$message'"
ampersand_test_fun -script_block {set-variable -scope 1 -name "message" -value "Script block message"}
wh "  TopScript message after:    '$message'"
wh "  Global message after:       '$global:message'"

wh
wh "Test 7 showed problem behavior"
wh
wh
wh "Test 8:"
wh "  Problem with with invoke() method with function in module"
wh "    ScriptBlock created at 'TopScript' scope"
wh "    TopScript -calls-> ModFunction -amp-calls-> Script -calls-> function -dot-calls-> ScriptBlock:"
wh
wh "  Expected behavior: ModFunction message after:  'Script block message'"
wh "  Problem behavior:  TopScript message after:    'Script block message'"
wh
wh "Results:"
$global:message = "Global message"
$message = "Top script message"
wh "  Global message before:      '$global:message'"
wh "  TopScript message before:   '$message'"
method_test_fun -script_block {set-variable -scope 1 -name "message" -value "Script block message"}
wh "  TopScript message after:    '$message'"
wh "  Global message after:       '$global:message'"

wh
wh "Test 8 showed problem behavior"