Powershell scriptblock 变量范围和模块的奇怪行为，有什么建议吗? [英] Strange behavior with Powershell scriptblock variable scope and modules, any suggestions?

问题描述

注意:我在 Windows Vista 上使用 PowerShell 2.0.

NOTE: I'm using PowerShell 2.0 on Windows Vista.

我正在尝试为 psake 添加对指定构建参数的支持，但我'我遇到了一些奇怪的 PowerShell 变量作用域行为，专门处理使用 Export-ModuleMember 导出的调用函数(这就是 psake 公开它的主要方法的方式).以下是一个用于说明的简单 PowerShell 模块(名为 repoCase.psm1):

I'm trying to add support for specifying build arguments to psake, but I've run into some strange PowerShell variable scoping behavior dealing specifically with calling functions that have been exported using Export-ModuleMember (which is how psake exposes it's main method). Following is a simple PowerShell module to illustrate (named 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"

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

To test the module, run the following sequence of commands (be sure you're in the same directory as the repoCase.psm1):

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

我预期的行为是我传递给 Test 的脚本块会影响 Test 的本地范围.它正在被点源化"，因此它所做的任何更改都应该在调用者的范围内.然而，这不是正在发生的事情，它似乎影响了它声明的范围.这是输出:

The behavior I expected was for the script block I passed to Test to affect the local scope of Test. It is being 'dotsourced' in, so any changes it makes should be within the scope of the caller. However, that's not what's happening, it seems to be affecting the scope of where it was declared. Here's the output:

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 作为模块导出，而只是声明函数并调用它，那么一切都会像我期望的那样工作.脚本块只影响 Test 的作用域，不修改全局作用域.

Interestingly, if I don't export Test as a module and instead just declare the function and invoke it, everything works just like I would expect it to. The script block affects only Test's scope, and does not modify the global scope.

我不是 PowerShell 专家，但有人可以向我解释这种行为吗?

I'm not a PowerShell guru, but can someone explain this behavior to me?

推荐答案

我一直在调查这个问题，这个问题出现在我正在做的一个项目中，并发现了三件事:

I have been investigating this problem, which has come up in a project I am working on, and discovered three things:

1. 该问题特定于模块.
   • 如果调用 scriptBlock 的代码实际位于 .psm1 文件中的任何位置，我们就会看到行为.
   • 如果调用 scriptBlock 的代码位于单独的脚本文件 (.ps1) 中，如果 scriptBlock 在 中传递，我们也会看到行为来自一个模块.
   • 如果调用 scriptBlock 的代码位于脚本文件 (.ps1) 中的任何位置，只要 scriptBlock 不是从模块传递的.

1. The issue is specific to modules.
   • If the code that invokes the scriptBlock is physically located anywhere within a .psm1 file, we see the behavior.
   • We also see the behavior if the code that invokes the scriptBlock is located in a separate script file (.ps1), if the scriptBlock was passed in from a module.
   • We do not see the behavior if the code that invoked the scriptBlock is located anywhere in a script file (.ps1), as long as the scriptBlock was not passed from a module.

我希望这能让您更清楚地了解这个问题，尽管我还没有提出解决方法.

I hope this sheds some more light on the problem, although I haven't quite gotten far enough to propose a workaround.

还有人安装了 PowerShell 1 吗?如果是这样，如果您可以检查它是否显示相同的行为，将会很有用.

Does anyone still have PowerShell 1 installed? If so, it would be useful if you can check whether it displays the same behavior.

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"

Here are the files for my test cases. To run them, create all four files in the same directory, and then execute "./all_tests.ps1" at the PowerShell ISE command line

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"

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