PowerShell ScriptBlock 到底是什么

PowerShell ScriptBlock 不是词汇闭合因为它不会关闭其声明环境中引用的变量。相反，它似乎利用了动态作用域和自由变量，这些变量在运行时绑定在 lambda 表达式中。

function Get-Block {
  $b = "PowerShell"
  $value = {"Hello $b"}
  return $value
}
$block = Get-Block
& $block
# Hello
# PowerShell is not written as it is not defined in the scope
# in which the block was executed.


function foo {
  $value = 5
  function bar {
    return $value
  }
  return bar
}
foo
# 5
# 5 is written $value existed during the evaluation of the bar function
# it is my understanding that a function is a named scriptblock
#  which is also registered to function:

对 ScriptBlock 调用 GetNewClosure() 会返回一个新的 ScriptBlock，该 ScriptBlock 会关闭所引用的变量。但这在范围和能力上都非常有限。

ScriptBlock 的分类是什么？

Per the docs，脚本块是“脚本文本的预编译块”。所以默认情况下你只是一个预先解析的脚本块，不多也不少。执行它会创建一个子作用域，但除此之外，就好像您内联粘贴了代码一样。因此，最合适的术语就是“只读源代码”。

Calling GetNewClosure固定在动态生成的模块上，该模块基本上携带调用时调用者范围内所有变量的快照GetNewClosure。它不是真正的闭包，只是变量的快照副本。脚本块本身仍然只是源代码，并且在调用它之前不会发生变量绑定。您可以根据需要在附加模块中添加/删除/编辑变量。

function GetSB
{
   $funcVar = 'initial copy'

   {"FuncVar is $funcVar"}.GetNewClosure()

   $funcVar = 'updated value'  # no effect, snapshot is taken when GetNewClosure is called
}

$sb = GetSB

& $sb  # FuncVar is initial copy

$funcVar = 'outside'
& $sb  # FuncVar is initial copy

$sb.Module.SessionState.PSVariable.Remove('funcVar')
& $sb  # FuncVar is outside