Repository navigation
Calling base class method in a System.Xml.XmlNode-derived custom class fails; invokes own method instead, resulting in infinite recursion #6386
Description
Activity
It seems to work, at least in simple cases, when you are extending a PowerShell class as in:
PS[1] (110) > class foo { [void] doit() {Write-Host "DOIT" }} PS[1] (111) > class bar : foo { [void] doit() {([foo] $this).doit()}} PS[1] (112) > $b.doit() DOITJason Shirk (@lzybkr) Thoughts?
Sorry, no idea what is going on here.
This is not specific to powershell class. It repros with a regular type added with
Add-Type:$code =@' public class Foo : System.Xml.XmlDocument { public override void LoadXml(string content) { System.Console.WriteLine("BLAH"); } } '@ Add-Type $code $foo = [Foo]::new() ([System.Xml.XmlDocument]$foo).LoadXml('<foo>bar</foo>') > BLAH
This is actually specpfic to types that derive from
System.Xml.XmlNode. The primary adapter of such a type is theXmlNodeAdapter, which is not optimizable (SiteBinderCanOptimizereturnsfalse). In such case, the invocation is done through theInvokemethod of the adapter, instead ofPSInvokeMemberBinder.InvokeDotNetMethod, and therefore, thePSMethodInvocationConstraintsis not respected.Reacted by Michael Klement- changed the title
[-]Calling base class method in a custom class fails; invokes own method instead, resulting in infinite recursion[/-][+]Calling base class method in a System.Xml.XmlNode-derived custom class fails; invokes own method instead, resulting in infinite recursion[/+]on Mar 14, 2018
The documented syntax for invoking a base-class method from a PS custom class is
([<base-class>] $this).<method>(), but that doesn't seem to work, as discovered in this SO question.Instead, the derived class' method itself is invoked, resulting in infinite recursion.
Update: The problem appears to be specific to
[System.Xml.XmlNode]-derived classes; see @daxian-dbw's comment below.A reflection-based workaround can be found in this answer.
Steps to reproduce
Expected behavior
The message should print once, and the XML string should be loaded into the instance via the call to the base-class method.
Actual behavior
The method keeps calling itself and eventually runs into a call-depth overflow.
Environment data