How to work with System.Manangement.Automation.Language... ast - powershell

Question

So I'm trying to create a custom PsAnalyzer rule for the office, and it's my first time using $ast based commands/variables. As a result I'm at a bit of a loss.
I've been using a couple of sites to get my head around the [System.Management.Automation.Language] object class, namely this, this, and this.
For testing purposes I'm using the function below - dodgy looking params intended.
Function IE {
[cmdletbinding()]
Param(
$Url,
$IEWIDTH = 550,
$IeHeight = 450
)
$IE = new-object -comobject InternetExplorer.Application
$IE.top = 200 ; $IE.width = $IEWIDTH ; $IE.height = $IEHEIGHT
$IE.Left = 100 ; $IE.AddressBar = $FALSE ; $IE.visible = $TRUE
$IE.navigate( "file:///$Url" )
}
Then with the code below, I'd expect $IEWIDTH as the only param to fail.
Function Measure-PascalCase {
<#
.SYNOPSIS
The variables names should be in PascalCase.
.DESCRIPTION
Variable names should use a consistent capitalization style, i.e. : PascalCase.
.EXAMPLE
Measure-PascalCase -ScriptBlockAst $ScriptBlockAst
.INPUTS
[System.Management.Automation.Language.ScriptBlockAst]
.OUTPUTS
[Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic.DiagnosticRecord[]]
.NOTES
https://msdn.microsoft.com/en-us/library/dd878270(v=vs.85).aspx
https://msdn.microsoft.com/en-us/library/ms229043(v=vs.110).aspx
https://mathieubuisson.github.io/create-custom-rule-psscriptanalyzer/
#>
[CmdletBinding()]
[OutputType([Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic.DiagnosticRecord[]])]
Param
(
[Parameter(Mandatory = $True)]
[ValidateNotNullOrEmpty()]
[System.Management.Automation.Language.ScriptBlockAst]
$ScriptBlockAst
)
Process {
$Results = #()
try {
#region Define predicates to find ASTs.
[ScriptBlock]$Predicate = {
Param ([System.Management.Automation.Language.Ast]$Ast)
[bool]$ReturnValue = $false
if ( $Ast -is [System.Management.Automation.Language.ParameterAst] ){
[System.Management.Automation.Language.ParameterAst]$VariableAst = $Ast
if ( $VariableAst.Left.VariablePath.UserPath -eq 'i' ){
$ReturnValue = $false
} elseif ( $VariableAst.Left.VariablePath.UserPath.Length -eq 3 ){
$ReturnValue = $false
} elseif ($VariableAst.Left.VariablePath.UserPath -cnotmatch '^([A-Z][a-z]+)+$') {
$ReturnValue = $True
}
}
return $ReturnValue
}
#endregion
#region Finds ASTs that match the predicates.
[System.Management.Automation.Language.Ast[]]$Violations = $ScriptBlockAst.FindAll($Predicate, $True)
If ($Violations.Count -ne 0) {
Foreach ($Violation in $Violations) {
$Result = New-Object `
-Typename "Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic.DiagnosticRecord" `
-ArgumentList "$((Get-Help $MyInvocation.MyCommand.Name).Description.Text)",$Violation.Extent,$PSCmdlet.MyInvocation.InvocationName,Information,$Null
$Results += $Result
}
}
return $Results
#endregion
}
catch {
$PSCmdlet.ThrowTerminatingError($_)
}
}
}
Export-ModuleMember -Function Measure-*
Instead I get:
Line Extent Message
---- ------ -------
6 $Url Variable names should use a consistent capitalization style, i.e. : PascalCase.
7 $IEWIDTH = 550 Variable names should use a consistent capitalization style, i.e. : PascalCase.
8 $IeHeight = 450 Variable names should use a consistent capitalization style, i.e. : PascalCase.
6 $Url Variable names should use a consistent capitalization style, i.e. : PascalCase.
7 $IEWIDTH = 550 Variable names should use a consistent capitalization style, i.e. : PascalCase.
8 $IeHeight = 450 Variable names should use a consistent capitalization style, i.e. : PascalCase.
Any ideas on what I'm doing wrong? I found another site here, if I use that method to test individual variables at a time, I get the results I'd expect to see.
To do that, add the following line at the end of the function IE,
[System.Management.Automation.Language.Parser]::ParseInput($MyInvocation.MyCommand.ScriptContents, [ref]$null, [ref]$null)
Then this code below will give you length numbers.
$stuffast = .\FunctionIe.ps1
$left = $Stuffast.FindAll({$args[0] -is [System.Management.Automation.Language.AssignmentStatementAst]},$true)
$left[0].Left.Extent.Text.Length
$left[0].Left.VariablePath.UserPath.Length

Answer 1

Unlike an AssignmentStatementAst, which has a Left and Right(-hand) value property, the ParameterAst has a Name and DefaultValue property, so you'll want to use Name in your predicate block:
$predicate = {
# ...
if ( $Ast -is [System.Management.Automation.Language.ParameterAst] ) {
[System.Management.Automation.Language.ParameterAst]$VariableAst = $Ast
if ( $VariableAst.Name.VariablePath.UserPath -eq 'i' ) {
$ReturnValue = $false
}
elseif ( $VariableAst.Name.VariablePath.UserPath.Length -eq 3 ) {
$ReturnValue = $false
}
elseif ($VariableAst.Name.VariablePath.UserPath -cnotmatch '^([A-Z][a-z]+)+$') {
$ReturnValue = $True
}
}
# ...
}
Alternatively, flip your predicate-logic around to search for VariableExpressionAst's where the parent node is one of AssignmentStatementAst or ParameterAst:
$predicate = {
param($ast)
$ValidParents = #(
[System.Management.Automation.Language.ParameterAst]
[System.Management.Automation.Language.AssignmentStatementAst]
)
if($ast -is [VariableExpressionAst] -and $ValidParents.Where({$ast -is $_}, 'First')){
[System.Management.Automation.Language.VariableExpressionAst]$variableAst = $ast
# inspect $variableAst.VariablePath here
}
return $false
}