[Laszlo-dev] [REVISED] For Review: Change 20080728-ptw-G Summary: Implement <setter>

[P T Withington]

On 2008-07-29, at 10:21EDT, André Bargull wrote:

> Do we want to allow non-literal attribute names for the  
> "super.setAttribute(..)" call? I'm just thinking about js2-setters  
> and our (possible) future plans to compile away the "setAttribute"- 
> mechanism with real js2-setters. I just want to prevent that users  
> make any non-sense with the "super.setAttribute"-stuff, so that we  
> may need to provide any scary backward compatibility thing in the  
> future. At least we should state that this is not supported and may  
> change in future versions..

Hm.  This is a good point.  We could just make this an error, I don't  
know if it is used anywhere already.  Although I think in theory you  
could still do this in JS2 because there is `intrisic::set(id, value)`  
and I would think you should be able to say:

   super[id] = value;

to invoke a super setter method at runtime.  Although, from your notes  
below, apparently as3 does not allow this.

> And it's also currently not possible in swf9 at all, see point (iii).

That's too bad.  Possibly a reason for ruling it out.  If this is  
really not used anywhere in code, I suppose now is as good a time as  
any to disallow it.

> Next problem I hit: what about "Function#call" and "Function#apply"?  
> swf8 gave a runtime error, swf9 a compile error. Point (i)

Ouch.  I guess I save myself a lot of trouble if I don't allow any of  
these crazy things.  Surely this pattern is not used in any existing  
code.

> And what is the expected behaviour when I attempt to call a non- 
> existing super-setter? swf9 emits a (native) runtime-error, the swf8  
> error was less "informative" (apart from the line number info).  
> Point (ii)

I think that's the best we can do.  This is no different than calling  
super in any other case where there is no super method.

> Otherwise approved!
>
>
> (i) using "call" or "apply"
>> <setter name="foo" args="newfoo">
>>    Debug.info("sub.set foo: %s", newfoo);
>>    super.setAttribute.apply(this, ["foo", newfoo]);
>>    //super.setAttribute.call(this, "foo", newfoo);
>> </setter>
> swf8 compilation - runtime error:
>> ERROR @LPP-5587.lzx#21: undefined object does not have a property  
>> 'apply'
> swf9 compilation - compile error:
>> |LPP-5587.lzx:22:5: Syntax error: the token "[" was not expected at  
>> this position.
>> Was expecting one of: (, .|
>
>
> (ii) using "super.setAttribute" without super-setter
>> <class name="sub" extends="base">
>>    <attribute name="bar" value="false" type="boolean" />
>>    <setter name="bar" args="newbar" >
>>      Debug.info("sub.set bar: %s", newbar);
>>      super.setAttribute("bar", newbar);
>>    </setter>
>>  </class>
> swf8 compilation - runtime error:
>> ERROR @LPP-5587.lzx#26: undefined object does not have a property  
>> 'call'
> swf9 compilation - runtime error in swf9.
>> ReferenceError: Error #1070: Method $lzc$set_bar not found in .$lzc 
>> $class_base
>
>
> (iii) non literal for attribute name:
>
>> <class name="sub" extends="base">
>>    <setter name="foo" args="newfoo">
>>      Debug.info("sub.set foo: %s", newfoo);
>>      var methname = "foo";
>>      super.setAttribute(methname, newfoo);
>>    </setter>
>>  </class>
> swf9 compilation - compile error:
>> |LPP-5587.lzx:22:5: Syntax error: the token "[" was not expected at  
>> this position.
>> Was expecting one of: (, .|
>
>
> On 7/29/2008 1:04 PM, P T Withington wrote:
>> [REVISED: I really think I got the change set up to date now.]
>>
>> Change 20080728-ptw-G by ptw at dueling-banjos.local on 2008-07-28  
>> 16:57:52 EDT
>>    in /Users/ptw/OpenLaszlo/dingdong-clean
>>    for http://svn.openlaszlo.org/openlaszlo/trunk
>>
>> Summary: Implement <setter>
>>
>> Bugs Fixed:
>> LPP-5587 'Improve LZX getter/setter to be more like conventional O- 
>> O languages'
>>
>> Technical Reviewer: a.bargull at intensis.de (pending)
>> QA Reviewer: promanik at laszlosystems.com (pending)
>>
>> Release Notes:
>>    There is a new tag available in classes and instances (<setter>)
>>    that can be used to define a setter for an attribute.  This tag
>>    can be used to override a built-in setter.  The overridden setter
>>    can be invoked by using `super.setAttribute`.
>>
>> Details:
>>    schema: allow <setter> in canvas and node
>>
>>    swf9stubs: use LzFormatter for prettier output
>>
>>    JavascriptGenerator, CodeGenerator, SWF9Generator: Transform
>>    `super.setAttribute(x, y)` to `super['$lzc$set_' + x](y)`.
>>
>>    NodeModel: Add support or the <setter> tag.
>>
>> Tests:
>>    Test case from bug, in swf8, dhtml, and swf9
>>
>> Files:
>> M      WEB-INF/lps/schema/lfc.lzx
>> M      WEB-INF/lps/lfc/debugger/swf9stubs.lzs
>> M      WEB-INF/lps/server/src/org/openlaszlo/sc/ 
>> JavascriptGenerator.java
>> M      WEB-INF/lps/server/src/org/openlaszlo/sc/CommonGenerator.java
>> M      WEB-INF/lps/server/src/org/openlaszlo/sc/SWF9Generator.java
>> M      WEB-INF/lps/server/src/org/openlaszlo/compiler/NodeModel.java
>>
>> Changeset: http://svn.openlaszlo.org/openlaszlo/patches/20080728-ptw-G.tar
>>