[IronPython] PrivateBindings fails to expose functions in internal classes, but not properties

[Richard Nienaber]

Thanks for providing the reproduction steps. I've had a look around the
source and it seems like the problem is happening somewhere between
CompilerHelpers.cs<https://github.com/IronLanguages/main/blob/master/Runtime/Microsoft.Dynamic/Generation/CompilerHelpers.cs#L368>
and
PythonBinder.cs<https://github.com/IronLanguages/main/blob/master/Languages/IronPython/IronPython/Runtime/Binding/PythonBinder.cs#L85>that
calls it.  If
the interface is not visible, it tries to return it's base type which is
null. If I just return the interface out of the GetVisibleType method before
it hits null, the message is displayed as intended.

It seems logic is needed to special case interfaces and/or handle the
PrivateBindings option but I don't know enough to say.

Richard

On Sun, Jan 9, 2011 at 4:42 AM, Leo Carbajal <desleo at gmail.com> wrote:

> Sorry to spam the list, but I did some more tracking on this and figured
> something out. I downgraded from 2.7b1 to 2.6.2 and my original example
> worked just fine in. I thought my woes were over, and then I ran into a
> similar problem in 2.6.2. It appears that IPy cannot cast an object to a
> different type, specifically an interface in 2.6.2, when the class is
> internal and you're working with PrivateBinding = true
>
> I logged it as http://ironpython.codeplex.com/workitem/29939 with the
> following example:
>
> internal interface IExample
> {
>     string Message { get; set; }
> }
>
> internal class Avatar : IExample
> {
>     public string Message { get; set;}
>
>     public Avatar()
>     {
>         Message = "I am an avatar.";
>     }
>
>     public void Hello(Avatar avatar)
>     {
>         Console.WriteLine("From Hello: " + Message);
>     }
>
>     public void Hi(IExample avatar)
>     {
>         Console.WriteLine("From Hi: " + Message);
>     }
> }
>
> Using the following python code:
> avatar = Avatar()
> avatar.Hello(avatar)
> avatar.Hi(avatar)
>
> avatar.Hello prints it's message as expected, but avatar.Hi fails with: System
> Error: object reference not set to instance of object.
>
> On Sat, Jan 8, 2011 at 6:07 PM, Leo Carbajal <desleo at gmail.com> wrote:
>
>> Ok, here's a clarification.
>>
>> Say you have this class:
>>
>> internal class ZMPReporter : IReporter
>>     {
>>         public string Setting { get; set; }
>>
>>         internal void Trixery(string mes, string mes1, string mes2, bool
>> thing)
>>         {
>>             Flash(mes, mes1, mes2, thing);
>>         }
>>
>>         public void Flash(string sender, string message, string recipient,
>> bool isAuthor)
>>         {
>>             ...
>>         }
>>     }
>>
>> It's a property of another class. In C# I would use it as follows:
>> caller.Reporter.Flash(..parameters..)
>>
>> If I call it in a normal IPy engine it fails to even recognize the caller
>> variable, which is fine and totally expected (and desired). In the
>> PrivateBinding scenario described I can call
>>
>> caller.Reporter.Setting and get the text data perfectly. When I try to
>> call caller.Reporter.Flash(), though, I get the System Error: object
>> reference not set problem. However, I can call
>> caller.Report._ZMPReporter__Trixery() just fine, which in turn calls Flash
>> for me.
>>
>> I don't mind using the name mangling overly, but I do mind having to make
>> internal proxies for perfectly good, already existing, functions. I can't
>> just make those methods internal because the IReporter interface demands
>> that they be public. If this was the only class that might give me problems
>> I might even look for a way around that, but the entire project uses
>> Interfaces extensively.
>>
>> On Sat, Jan 8, 2011 at 5:36 PM, Leo Carbajal <desleo at gmail.com> wrote:
>>
>>> Hello all,
>>>
>>> Almost I thought I could have my cake and eat it too. I have a large
>>> client-server project written in C# that I wanted to be able to script with
>>> IronPython. The biggest requirement was that I wanted external admins to be
>>> able to provide scripts for the server to augment its functions. However, I
>>> don't want them to have full access to the server API so I resigned myself
>>> to write the project with everything Internal and then build public facing
>>> classes for the functionality I wanted to expose. This, I know, to work
>>> fine.
>>>
>>> however, I still want to be able to use scripts on the server myself, for
>>> other things. I ended up using two engines, one with PrivateBinding on and
>>> one without. The one with PrivateBinding set to true can see all private and
>>> internal members but whenever I try to call a function from IronPython I get
>>> an exception of "System Error: Object reference not set to an instance of an
>>> object." It's weird because I can call on properties and get their values,
>>> but not functions. If I do a dir() on the class, and the member, IronPython
>>> can clearly see what they are and that they exist. If it helps, the class
>>> i'm trying to access is internal but has all public members (for
>>> interfaces).
>>>
>>> I guess my question is whether this behavior is intentional or not. Being
>>> able to use my API on one engine for actual server work while providing a
>>> different one for plugin\event hook writers, would help tremendously.
>>>
>>
>>
>
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