I can answer both in one: To be able to use IronPython to create data classes,
marked up with attributes, to be consumed by APIs probably written in something
other than IronPython.
That's it.. quite simple.
Example of such an API: LINQ to SQL. Or LINQ to whatever, since outside of of
Objects and XML, things pretty much end up with mapping metadata and attributes
are one of the first places to look for that.
And so, in light of the DLR effort, and the general push to make the static
languages be able to work well with the dynamics, I think it's only right that
the DLR languages be able to expose their dynamic types in such as way as to be
transparent to the static languages. That's why I pointed out that Type is an
abstract class and the MemberInfo subclasses themselves appear to be
subclassable. It really appears that the API is there, waiting to be
implemented.
Otherwise, really, the dynamic languages are completely unusable for certain
APIs -- they just don't interact with the reflection API in such a way that
libraries can consume in a reasonable, language-neutral manner.
________________________________
From: [EMAIL PROTECTED] on behalf of Curt Hagenlocher
Sent: Wed 7/23/2008 4:39 PM
To: Discussion of IronPython
Subject: Re: [IronPython] IronPython Post 2.0 Roadmap
So, we had a brief hallway discussion today about this topic, and the upshot is
that I'm interested in hearing your "real world" use cases for
a) attributes, and
b) static type generation in general
By "use case", I mean a scenario that's specifically relevant to you today. By
"relevant", I mean that it would be *nice* to be able to write a PowerShell
extension in Python, but if you didn't end up writing the extension in another
language, then it doesn't really count for what I'm looking for. :)
On Mon, Jul 21, 2008 at 4:16 PM, Keith J. Farmer <[EMAIL PROTECTED]> wrote:
We are talking about *new* features, but you're limiting yourself to
existing APIs?
If, for the sake of working nicely with the DLR, the existing
reflection API needs to be modified to deal with a more dynamic world, that's
not outside the realm of possibility in my books. After all, there has always
been talk of IP being able to expose static types for consumption outside of
IP. I don't see that this is any less possible now than it was at the start.
Incidentally, Type is an abstract class. Also, ParameterInfo isn't
sealed, and implements ICustomerAttributeProvider, which is a public interface:
public interface ICustomAttributeProvider
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Reflection.ICustomAttributeProvider>
{
// Methods
object
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Object>
[] GetCustomAttributes
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Reflection.ICustomAttributeProvider/GetCustomAttributes(Boolean):Object%5b%5d>
(bool
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Boolean>
inherit);
object
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Object>
[] GetCustomAttributes
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Reflection.ICustomAttributeProvider/GetCustomAttributes(System.Type,Boolean):Object%5b%5d>
(Type
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Type>
attributeType, bool
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Boolean>
inherit);
bool
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Boolean>
IsDefined
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Reflection.ICustomAttributeProvider/IsDefined(System.Type,Boolean):Boolean>
(Type
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Type>
attributeType, bool
<http://www.aisto.com/roeder/dotnet/Default.aspx?Target=code://mscorlib:2.0.0.0:b77a5c561934e089/System.Boolean>
inherit);
}
So I think, actually, that this could be done without changing much if
any external API. They'd probably need to change some of the internals to
return dynamic variants of the info types, but I think that's doable.
________________________________
From: [EMAIL PROTECTED] on behalf of Harry Pierson
Sent: Mon 7/21/2008 12:59 PM
To: Discussion of IronPython
Subject: Re: [IronPython] IronPython Post 2.0 Roadmap
All of the many overloads of GetCustomAttributes
(http://msdn.microsoft.com/en-us/library/system.attribute.getcustomattributes(VS.85).aspx)
need some type of static type info (Type, MemberInfo, ParameterInfo). So
supporting custom attributes would require some type of static class as Michael
mentions below.
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael
Foord
Sent: Monday, July 21, 2008 12:48 PM
To: Discussion of IronPython
Subject: Re: [IronPython] IronPython Post 2.0 Roadmap
Keith J. Farmer wrote:
> Attributes can be applied to more than just types -- members,
> parameters, return values (as I recall), etc.
But those all presuppose a static type - right?
IronPython could generate a static class in the compile phase where .NET
attributes are used. Python decorator syntax could be used - class
decorators are now part of Python 2.6 and no-one would object to you
sneaking them into Python 2.5...
Parameter and return type attributes could still use a method decorator
to apply them.
Michael
>
>
------------------------------------------------------------------------
> *From:* [EMAIL PROTECTED] on behalf of Curt Hagenlocher
> *Sent:* Mon 7/21/2008 9:51 AM
> *To:* Discussion of IronPython
> *Subject:* Re: [IronPython] IronPython Post 2.0 Roadmap
>
> "Availability of a static type" not because IronPython would need to
> access one but because it would need to expose one.
>
>
> On Mon, Jul 21, 2008 at 9:44 AM, Keith J. Farmer <[EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]>> wrote:
>
> You can create your own attribute classes, for whatever markup.
> Particularly since LINQ-to-*, where they often are used to
> annotate data classes with strings, etc (not references to types).
>
> In any event, why does "availability of a static type" enter into
> this? IP can access static types just as well as any other .NET
> language (System.Math comes to mind). The motivation in general
> is to make IP a better producer for CLR types, rather than just a
> consumer, and attributes are an increasingly important thing to
> support.
>
> As for expression trees and extension methods, those are to make
> IP a better consumer of a very important API (LINQ and the
> IQueryable stack from .NET 3.5).
>
> To be honest, once those 3 features are available in IP, I think
> it would be on par with the mainstream languages in being very
> usable in an exclusive sense.
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]>
> [mailto:[EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]>] On Behalf Of Harry
> Pierson
> Sent: Sunday, July 20, 2008 11:14 PM
> To: Discussion of IronPython
> Subject: Re: [IronPython] IronPython Post 2.0 Roadmap
>
> Can you give me some examples where you would use these? The
> problem I see is that many scenarios (WCF contracts, XML
> serialization just to name two) where people want to use a custom
> attribute depends on the availability of a static type.
>
> Harry
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]>
> [mailto:[EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]>] On Behalf Of Keith J.
> Farmer
> Sent: Saturday, July 19, 2008 8:13 PM
> To: Discussion of IronPython
> Subject: Re: [IronPython] IronPython Post 2.0 Roadmap
>
> votes++
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]>
> [mailto:[EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]>] On Behalf Of Michael
> Foord
> Sent: Saturday, July 19, 2008 10:38 AM
> To: Discussion of IronPython
> Subject: Re: [IronPython] IronPython Post 2.0 Roadmap
>
> Sanghyeon Seo wrote:
> > 2008/7/20 Harry Pierson <[EMAIL PROTECTED]
> <mailto:[EMAIL PROTECTED]>>:
> >
> >> Hosting features are all done via the DLR, so that's a separate
> team. As for
> >> "ability to interact with the rest of the .Net framework", can
> you be more
> >> specific about what you're looking for in that space? What
> *isn't* IPy doing
> >> that you want it to?
> >>
> >
> > .NET attributes?
> >
> >
> +1 :-)
>
> Michael
>
> --
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