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Re: [aspectj-users] Intertype declaration name mangling - for or against?
I'm wondering, is it interesting that I proposed it because it seems like it would cause me problems with all the ITDs I use, or because it just seems problematic in general? I think in my personal use cases I have ITDs with very specific behavior which is unlikely to cause many name clashes, and since they are private fields if name clashes were to occur re-factoring the the code would be rather simple. I did think of one potential problem though. Lets say I have an ITD that handles object selection. 

public interface SelectAction{

  public void select(Object selected);

}

public aspect SelectActionAspect{

  public Object SelectAction.selected;

  public void SelectActoin.select(Object selected){
    this.selected = selected;
  }

}
Pretty straight forward stuff, an interface and a default implementation. Now, I'm not worried that I might have a second ITD that would also inject a field named selected, but what if that default behavior didn't work for me and I wanted to do something to the object when it is selected. What happens if I do: 

public class SelectImpl implements SelectAction{

  private Object selected;

  public void select(Object selected){
    System.out.println("I'm selected " + selected);
     this.selected = selected;
   }

}
What happens there? Do I get an error that I can't add a field with that name, which would be bad because I might need to have a field named selected available for introspection? Does the implementation field take precedence? What then happens if I have a second method in my ITD that accesses the injected field? Does that method now refer to the new overridden field? I think maybe it makes the most sense that if a conflict like that arose the ITD wouldn't be applied at all, but that would have to be very obvious to the user in order to avoid a lot of confusion. Maybe an annotation could be added that allowed one to selectively turn off ITDs for a particular type and the compiler would raise an error on a field name conflict unless that annotation was used: 

public class SelectImpl implements @ApplyITD(false) SelectedAction{
  ...
}

Just some thoughts....

On Nov 20, 2009, at 2:12 PM, Andy Clement wrote:


Thanks Dave and Ramnivas.  yes I have progressed on the new intertype
syntax, but a mountain of testing to do there.  It is interesting
about you (Dave) proposing the default be switched to non-mangling -
I'm nervous about that (from a backwards compatibility point of view I
think), but not entirely against it.  Intertype fields are far far far
far more straightforward than intertype methods, so that's where I'd
play around first and that would seem to help a lot with these
frameworks.

Andy

2009/11/20 Ramnivas Laddad <ramnivas@xxxxxxxxxxxxxxx>:

I am all for this. Mangled names create problems with JPA and such.
I guess one issue to consider is what happens when two aspects want to introduce a same-named field with a directive to not mangle, especially if both aspects are from third-party libraries. This is quite unlikely to occur in practice, but we may need to address it somehow. I wonder if the 'declare 
precedence' can be an arbitrator here.
-Ramnivas
On Thu, Nov 19, 2009 at 10:54 AM, Andy Clement <andrew.clement@xxxxxxxxx > 
wrote:


I'm possibly going to review our approach to intertype declaration
naming. The names are currently mangled deliberately to preserve some of the 'rules' that AspectJ defines. For example, private field itds 
have mangled names because the field is private to the aspect and
shouldn't be visible as a 'regular' private field in the target. This also enables two aspects to ITD the same private field and there is no 
clash in the target type.

However, since those rules were defined a long time ago, things have
changed and various frameworks are looking at members via reflection, for purposes of invocation or automatic persistence. The mangling is 
unhelpful here.

I *thinking* about allowing non-mangled names, possibly with a
directive annotation in the aspect that says "do not mangle these, I
know what I'm doing and there won't be a problem".

Basically I wanted to collect any thoughts from you guys?
I suspect that the some of the scenarios AspectJ worries about rarely happen in practice - have you ever ITD'd the same named private field 
from two aspects onto the same type?  (AspectJ can continue to
warn/error when it sees this about to happen of course)

cheers,
Andy
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