[Ironpython-users] Binding problem with default parameters in public classes

Tue Aug 30 06:42:55 EDT 2016

Hi, all,

I just tested it with C#, with different results:

Using the dynamic keyword, it seems that C# using “dynamic” does not honor the optional parameter in any “inherited” case, it only works when the method implementation also provides the default parameter. ☹

This closely matches the behavior of the “normal” C# compiler, which delivers compiler errors in those cases – it works when I either have the interface or ABC as type, or the method implementation also has the default parameter declared. It also chooses the default value depending on the variable type.

Thus, it seems that C# is even more restrictive than IronPython right now, at least when the “dynamic” keyword is used.

Just as a side note, we successfully worked around the problem in our use case, so there is no urgent fix necessary, it was more some kind of curiosity of which semantics are considered “correct”. As changing anything might be a breaking change, I suggest we apply it only in 3.x (in case we fix anything).

The output of the extended, attached example is:

InternalImpl:
Internal: Param: 1 Text: mit text
Internal: Param: 2 Text: <defaultItf>
Internal: Param: 11 Text: See Sharp!
Keine Überladung für die DoSomething-Methode nimmt 1-Argumente an.
Internal: Param: 21 Text: <defaultItf>

PublicImpl:
Public: Param: 1 Text: mit text
DoSomething() takes exactly 2 arguments (1 given)
Public: Param: 11 Text: See Sharp!
Keine Überladung für die DoSomething-Methode nimmt 1-Argumente an.
Public: Param: 21 Text: <defaultItf>

PublicImplWithDefault:
PublicDefault: Param: 1 Text: mit text
PublicDefault: Param: 2 Text: <defaultImpl>
PublicDefault: Param: 11 Text: See Sharp!
PublicDefault: Param: 12 Text: <defaultImpl>
PublicDefault: Param: 21 Text: <defaultItf>
PublicDefault: Param: 24 Text: <defaultImpl>
PublicDefault: Param: 28 Text: <defaultImpl>

PublicAbcInternalImpl:
InternalABC: Param: 1 Text: mit text
InternalABC: Param: 2 Text: <defaultABC>
InternalABC: Param: 11 Text: See Sharp!
Keine Überladung für die DoSomething-Methode nimmt 1-Argumente an.
InternalABC: Param: 25 Text: <defaultABC>

PublicAbcPublicImpl:
PublicABC: Param: 1 Text: mit text
DoSomething() takes exactly 2 arguments (1 given)
PublicABC: Param: 11 Text: See Sharp!
Keine Überladung für die DoSomething-Methode nimmt 1-Argumente an.
PublicABC: Param: 25 Text: <defaultABC>

PublicAbcPublicImplWithDefault:
PublicABC: Param: 1 Text: mit text
PublicABC: Param: 2 Text: <defaultImpl>
PublicABC: Param: 11 Text: See Sharp!
PublicABC: Param: 12 Text: <defaultImpl>
PublicABC: Param: 25 Text: <defaultABC>

Best regards

Markus Schaber

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From: Slide [mailto:slide.o.mix at gmail.com]
Sent: Tuesday, August 30, 2016 12:09 PM
To: Markus Schaber; Discussion of IronPython
Subject: Re: [Ironpython-users] Binding problem with default parameters in public classes

I can see this both ways (bug and not a bug), so let's err on the side of bug and see if we can make the behaviour match C#.

On Mon, Aug 29, 2016, 23:53 Markus Schaber <m.schaber at codesys.com<mailto:m.schaber at codesys.com>> wrote:
Hi, Slide,

Using a public abstract base class produces the same result: If the derived class is internal, the call works fine, if the derived class is public, the call does not work.

Best regards

Markus Schaber

CODESYS® a trademark of 3S-Smart Software Solutions GmbH

Inspiring Automation Solutions
________________________________
3S-Smart Software Solutions GmbH
Dipl.-Inf. Markus Schaber | Product Development Core Technology
Memminger Str. 151 | 87439 Kempten | Germany
Tel. +49-831-54031-979 | Fax +49-831-54031-50

E-Mail: m.schaber at codesys.com<mailto:m.schaber at codesys.com> | Web: codesys.com<http://www.codesys.com> | CODESYS store: store.codesys.com<http://store.codesys.com>
CODESYS forum: forum.codesys.com<http://forum.codesys.com>

Managing Directors: Dipl.Inf. Dieter Hess, Dipl.Inf. Manfred Werner | Trade register: Kempten HRB 6186 | Tax ID No.: DE 167014915
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From: Slide [mailto:slide.o.mix at gmail.com<mailto:slide.o.mix at gmail.com>]
Sent: Monday, August 29, 2016 4:24 PM
To: Markus Schaber; Discussion of IronPython
Subject: Re: [Ironpython-users] Binding problem with default parameters in public classes

What happens if it's an abstract base class instead of an interface?

On Mon, Aug 29, 2016, 03:25 Markus Schaber <m.schaber at codesys.com<mailto:m.schaber at codesys.com>> wrote:
Hi,

Our tests recently caught a strange regression in our application. One can make existing scripts fail by changing an internal class to public.

The attached program reproduces the issue. The problem is that the method has optional parameters, but those are only declared at the interface.

Now, when the class changes from “internal” to “public”, IronPython binds directly to the public methods without considering the interfaces any more, and thus does not recognize the optional parameters.

Now, the question is whether this could be considered a bug in IronPython, or whether it should be considered a bug to implement an interface method without replicating the default parameter values…

Best regards

Markus Schaber

CODESYS® a trademark of 3S-Smart Software Solutions GmbH

Inspiring Automation Solutions
________________________________
3S-Smart Software Solutions GmbH
Dipl.-Inf. Markus Schaber | Product Development Core Technology
Memminger Str. 151 | 87439 Kempten | Germany
Tel. +49-831-54031-979 | Fax +49-831-54031-50

E-Mail: m.schaber at codesys.com<mailto:m.schaber at codesys.com> | Web: codesys.com<http://www.codesys.com> | CODESYS store: store.codesys.com<http://store.codesys.com>
CODESYS forum: forum.codesys.com<http://forum.codesys.com>

Managing Directors: Dipl.Inf. Dieter Hess, Dipl.Inf. Manfred Werner | Trade register: Kempten HRB 6186 | Tax ID No.: DE 167014915
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