[Development] QString behavior change

[Oswald Buddenhagen]

On Thu, Jul 30, 2015 at 08:37:28AM -0700, Thiago Macieira wrote:
> On Thursday 30 July 2015 11:47:16 Olivier Goffart wrote:
> > On Thursday 30. July 2015 09:38:12 Gerhard Scheikl wrote:
> > > Hi
> > > 
> > > The behavior of QString::trimmed has changed from 5.3.2 to 5.5.
> > > .trimmed() on an empty string (" ") makes it null
> > > .trimmed() on an empty string ("") doesn't make it null
> > > 
> > > Is this intended or a bug?
> > 
> > This is caused by 54da2b2911ace652dbd2c8ea852c5b8c47ab09c8 in qtbase.
> > 
> > I don't think it was intended.
> 
> Actually, it was. Trimming a string that doesn't need trimming returns the 
> original string. An empty string doesn't need trimming, therefore you get 
> exactly what you had.
> 
> But PLEASE stop relying on functions that mutate strings to reliably retain or 
> fail to retain the nullness of a string. Unless the documentation for the 
> particular function makes a distinction between null and not null, assume it 
> will behave arbitrarily and will change in behaviour.
>
well, that recommendation is reasonable in face of the status quo, but 
i think we should (and could) do a better job at preserving nullness.
there are only a handful of cases where the choice is arbitrary, and we
can clearly document them.