[Kde-bindings] KSharedConfig multiple matches

[Stefano Crocco]

On Friday 29 January 2010, David Palacio wrote:
> |$ irb
> |irb(main):001:0> kdeapp
> |=> #<KDE::Application:0x7ff8a870b158 objectName="irb">
> |irb(main):002:0> Qt.debug_level = 2
> |=> 2
> |irb(main):003:0> KDE::Global.config.group 'Recent'
> |classname    == KGlobal
> |
> |:: method == config
> |
> |-> methodIds == [#<Qt::Internal::ModuleIndex:0x7ff8962612b8 @smoke=8,
> |@index=1343>]
> |candidate list:
> |        static KSharedPtr<KSharedConfig> KGlobal::config()  (smoke: 8
> |index: 1343)
> |matching => smoke: 8 index: 1343
> |match => 1343 score: 0
> |Resolved to id: 1343
> |setCurrentMethod(smokeList index: 8, meth index: 1343)
> |classname    == KSharedConfig
> |
> |:: method == group
> |
> |-> methodIds == [#<Qt::Internal::ModuleIndex:0x7ff896260a70 @smoke=8,
> |@index=489>, #<Qt::Internal::ModuleIndex:0x7ff896260a48 @smoke=8,
> |@index=490>, #<Qt::Internal::ModuleIndex:0x7ff896260a20 @smoke=8,
> |@index=492>, #<Qt::Internal::ModuleIndex:0x7ff8962609f8 @smoke=8,
> |@index=493>] candidate list:
> |        KConfigGroup KConfigBase::group(const QString&)             
> |(smoke: 8 index: 489)
> |        KConfigGroup KConfigBase::group(const char*)                
> |(smoke: 8 index: 490)
> |        const KConfigGroup KConfigBase::group(const QString&) const 
> |(smoke: 8 index: 492)
> |        const KConfigGroup KConfigBase::group(const char*) const    
> |(smoke: 8 index: 493)
> |matching => smoke: 8 index: 489
> |      const QString& (s)
> |match => 489 score: 4
> |matching => smoke: 8 index: 490
> |      const char* (s)
> |match => 490 score: 1
> |matching => smoke: 8 index: 492
> |      const QString& (s)
> |multiple methods matching, this is an error
> |match => 492 score: 4
> |matching => smoke: 8 index: 493
> |      const char* (s)
> |match => 493 score: 1
> |TypeError: can't convert false into Integer
> |        from /home/kde/ruby/lib/Qt/qtruby4.rb:2725:in `findAllMethods'
> |        from /home/kde/ruby/lib/Qt/qtruby4.rb:2725:in `do_method_missing'
> |        from (irb):3:in `method_missing'
> |        from (irb):3
> |        from :0

I reported this issue a couple of months ago, but it hasn't been fixed as yet, 
even if its cause has been understood. It seems that the new smoke generator 
differentiates between const and non-const version of C++ methods, while the 
old generator didn't. This means that now it's not enough to examine the 
argument list to find out which C++ method to call, which is what qtruby does.

In the last days, I tried to fix the issue myself and (at least at a first 
galance) I succeeded. The attached patch changes the qtruby.cpp and qtruby.rb 
files to allow to distinguish among overloaded methods which only differ 
because of the const-ness either of the methods themselves or of their 
arguments.

This is a summary of the changes I made:

- qtruby.cpp

Defined a isConstMethod method for the Qt::Internal module which returns true
if the method corresponding to the index passed as argument has the const 
attribute and false otherwise

- qtruby.rb

Changed the way do_method_missing behaves if it finds two methods with the 
same score: now, instead of giving an error immediately, it checks whether one
is const and the other isn't (using the isConstMethod from qtruby.cpp). If 
this is the case, the non-const method is chosen (which, if I understand 
correctly, is what happened with the old smoke). If both are const, or not 
const, the behaviour remains the same.

Initially, I thought the above changes should have been enough. However, it 
wasn't so. In particular, while KDE::SharedConfig#group worked, 
KDE::ConfigGroup.new didn't. I think the reason is that there's also an 
ambiguity with const/non const arguments. To avoid it, I also changed the 
Internal.checkarg method, so that a const argument score one less than a non 
const argument of the same type would. Of course, to avoid clashes between 
score for a const argument of one type and a non-const argument of another 
type, I had to change the score of all of them, so that now they differ by 
two, rather than by one as it used to be.

I don't know whether this changes work correctly. I tried them with my 
application and they seem to work without drawbacks, but I must admit I had 
not much time to test them. However, I hope they can be useful.

Stefano
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