IndexedSlots in combination with StatefulTraits

Hi Torsten, 

   the problem is defining the behavior expected from the set of messages:

Today we have 3 (yes 3.... awful) they are to keep compatibility with the tools, we have to continue improving them.

- allSlots: returns all the slots defined in the hierarchy, in the same class and in all the traits used in the hierarchy.

- localSlots: returns the slots that are defined in the own class without the ones in the traits.

- slots: returns the slots that are defined in the class and not in the superclasses.

The last message is the one that is disturbing, it is kept for compatibility with the old behavior. In my opinion, localSlots should be removed, and slots behave like localSlots. 

It requires to change the tools. 

If we need to know where the slots are defined we can ask the slots, the slots know which is the class using the slot and where it is defined. 

So, I will like to improve in any way. 

About the implementation I like the one in #localSlots.

But it requires some work or letting the stuff broken until we fix them.

Cheers,

Pablo

On Tue, Jul 17, 2018 at 10:19 AM Torsten Bergmann <[hidden email]> wrote:

I guess I found a bug in accessing Slots using #slots in combination with IndexedSlots and traits.
To reproduce use latest Pharo 7 (Build 1126)

First create a class with a slot, note that the slot needs to be :

Object subclass: #ClassA
        slots: { IndexedSlot named: #upper }
        classVariables: { }
        package: 'Slot-Bugs'

As it is the first slot it internally receives an index 1 as you can check with "ClassA slots first".

Now define a stateful trait with another indexed slot:

        Trait named: #StatefulTrait
                uses: {}
                slots: { IndexedSlot named: #slotFromTrait }
                category: 'Slot-Bugs'   

And create a new subclass using the new Trait

        ClassA subclass: #ClassB
                uses: StatefulTrait
                instanceVariableNames: ''
                classVariableNames: ''
                package: 'Slot-Bugs'     


1. when you evaluate "ClassA slots"  it returns {#FirstSlot => Slot} which is correct
2. when you evaluate "StatefulTrait slots"  it returns {#slotFromTrait => Slot} which is correct
3. when you evaluate "ClassB allSlots"  returns  "an OrderedCollection(#upper => InstanceVariableSlot #slotFromTrait => InstanceVariableSlot)" which is OK

but 

4. when you evaluate "ClassB slots" it returns  {#slotFromTrait => InstanceVariableSlot} which is NOT correct as class B does not define the slot, it is defined in the trait


So I think 4. is wrong and reasons is the implementation of #slot:

  slots
        "I remove the slots comming from a traitComposition"
        ^ super slots reject:[ :e  | self traitComposition slots includes:e ]   

If you debug you will notice that

   super slots                   returns our #slotFromTrait with an index of 2 while
   self traitComposition slots   returns our #slotFromTrait with an index of 1 while

which is the same #slotFromTrait but a different index - therefore it does not get removed.


Dont know what is the best way to fix this without any side effects. Commenst and help appreciated.

Thanks
T.

--

Pablo Tesone.
[hidden email]