643455 - Consider refining/documenting/supporting describeTypeJSON

Status: RESOLVED WONTFIX

(Tamarin Graveyard :: Virtual Machine, defect)

Description

[Steven Johnson]

When the implementation of describeType() was moved from Flash into Tamarin, describeTypeJSON() came into being as a helper class for implementation. It wasn't intended for public use, but I inadvertently left it visible to the public, and people have discovered it (see: http://www.tillschneidereit.de/2009/11/22/improved-reflection-support-in-flash-player-10-1/)

As it turns out, there's a desire and need for the improved reflection capabilities in describeTypeJSON(), so we should consider cleaning it up (it's a little rough as-is) and making it an official API for future releases of Flash.

Comment 1

[P T Withington]

OpenLaszlo is using this API to implement a `subclassof` operator.  The XML-based describeType interface is much too heavy-weight, so we were happy to find that we could ask for just the information we needed with describeTypeJSON.  The only other way we could think of to compute if one class was a subclass of another (including interfaces) was to create a 'test instance' of the class in question, which is also very inefficient.

So +1 from our team to make this a documented/maintained public API.

Comment 2

[Edwin Smith]

Would you be willing to offer one or a few test cases that demo how you use it?  ABC would be great, other formats acceptable to if we can get ABC from them.

Comment 3

[André Bargull [:anba]]

Attachment: use case of "describeTypeJSON()" in OpenLaszlo

Use case of "describeTypeJSON()" in OpenLaszlo to support subclassof() operation.

Comment 4

[Felix S. Klock II [:pnkfelix, :fklock]]

People are noting the performance difference between the two.  E.g. see this blog post about JSON performance:

http://compiler.kaustic.net/lab/?p=55

"""
  flash.utils.describeType vs avmplus.describeTypeJSON

  The avmplus.describeTypeJSON trick is very important here… it makes the difference between 77 ms and 10 ms!
"""

Comment 5

[Steven Johnson]

Seems like we should really consider doing the cleanup/documentation work for Serrano, if schedule still permits.

Comment 6

[Christopher Mason]

Not being able to reflect on private and protected methods is a real drag.  In particular: we use the reflection data for a DI framework, but we're currently restricted to using only public setters/functions for injection; this exposes internal parts of the classes that we'd rather be private/protected.  Would you consider adding flags for INCLUDE_PROTECTED and INCLUDE_PRIVATE?

from http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/utils/package.html#describeType%28%29 :
  Note: describeType() only shows public properties and methods, and will not show properties and methods that are private, package internal or in custom namespaces.

Comment 8

[Felix S. Klock II [:pnkfelix, :fklock]]

(In reply to comment #6)
> Not being able to reflect on private and protected methods is a real drag. 
> In particular: we use the reflection data for a DI framework, but we're
> currently restricted to using only public setters/functions for injection;
> this exposes internal parts of the classes that we'd rather be
> private/protected.  Would you consider adding flags for INCLUDE_PROTECTED
> and INCLUDE_PRIVATE?
> 
> from
> http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/
> utils/package.html#describeType%28%29 :
>   Note: describeType() only shows public properties and methods, and will
> not show properties and methods that are private, package internal or in
> custom namespaces.

That sounds like a different bug to me, or at least a serious bit of scope creep.

This bug, to my mind, is about provide the *same* information that describeType provides, just in a different serialized format.

Your suggestion is to *expand* the potential information available via our reflection API; that probably would require getting more significant review of the implications of such information exposure.

Comment 9

[NemoStein]

Is this bug under consideration yet?
It's been more than a year already...

Comment 10

[Sylvestre Ledru [:Sylvestre]]

Tamarin isn't maintained anymore. WONTFIX remaining bugs.