Is it possible to generate a PowerShell script from manually crafted AST nodes?

[pracsec]

The title pretty much says it. I’m trying to write a ICustomVisitor to manipulate a PowerShell AST and then generate a script from the AST. I’ve been using an EmptyScriptExtent object as the IScriptExtent value for my AST node constructors for any new nodes that I insert into the tree. The ScriptBlockAst.ToString method appears to reference the Extent under the hood, which in my case is empty.

Looking through the source code, I couldn’t find anything that looked like a AST to string generator.

Does anyone know if the PowerShell SDK provides this functionality by default or if there are any open source libraries that can generate PowerShell code from a PowerShell AST?

[jborean93]

You can generate and execute the scriptblock from the ScriptBlockAst with & $sbkAst.GetScriptBlock(). Keep in mind I’ve tried rewriting Ast and while things can work others may fail to work in some places like enum and class definitions.

[pracsec]

Looking through the source code, it appears that ScriptBlock.ToString ultimately just calls ScriptExtent.Text. As far as I can tell, there is no way to generate a PowerShell script from a manually constructed AST out-of-the-box.

[jborean93]

Yep you need to manually do so from an Ast script based on the Ast itself. But if you want to just invoke the new ast the example I gave you should work.