Extracting the function body from a file using powershell - powershell

Question

How can i extract the content of a powershell function definition?
Suppose the code is like,
Function fun1($choice){
switch($choice)
{
1{
"within 1"
}
2{
"within 2"
}
default{
"within default"
}
}
}
fun1 1
I want only the contents of the function definition and no other text.

Answer 1

Using PowerShell 3.0+ Language namespace AST parser:
$code = Get-Content -literal 'R:\source.ps1' -raw
$name = 'fun1'
$body = [Management.Automation.Language.Parser]::ParseInput($code, [ref]$null, [ref]$null).
Find([Func[Management.Automation.Language.Ast,bool]]{
param ($ast)
$ast.name -eq $name -and $ast.body
}, $true) | ForEach {
$_.body.extent.text
}
Outputs a single multi-line string in $body:
{
switch($choice)
{
1{
"within 1"
}
2{
"within 2"
}
default{
"within default"
}
}
}
To extract the first function definition body regardless of name:
$body = [Management.Automation.Language.Parser]::ParseInput($code, [ref]$null, [ref]$null).
Find([Func[Management.Automation.Language.Ast,bool]]{$args[0].body}, $true) | ForEach {
$_.body.extent.text
}
To extract the entire function definition starting with function keyword, use $_.extent.text:
$fun = [Management.Automation.Language.Parser]::ParseInput($code, [ref]$null, [ref]$null).
Find([Func[Management.Automation.Language.Ast,bool]]{$args[0].body}, $true) | ForEach {
$_.extent.text
}