On 02:39 pm, k.kelly.gor...@gmail.com wrote: >On Thu Oct 8 20:08:12 EDT 2009, Glyph Lefkowitz <glyph at >twistedmatrix.com> wrote: >>On Thu, Oct 8, 2009 at 7:59 PM, Mark Visser <markv at lumierevfx.com> >>wrote: >> >> > I've been bitten a couple times by twisted's use of old-style >>classes. >> > Now that Jython is finally off the 2.2 branch, is there any real >>reason >> > to stay backwards compatible? >> > >> >>Changing a class from old-style to new-style is an incompatible >>change. The >>difficulty is that if existing libraries use a particular class and >>inherit >>from it, changing the class to be new-style can have effects from >>changing >>how their descriptors work to causing an exception when their module >>is >>imported. >... >> >>If old-style classes can be evolved into new-style classes while >>somehow >>following this policy, that would be great. The problem is that >>providing >>compatibility at this level is time-consuming and difficult. One >>problem in >>particular is that we don't want to litter the codebase with lots of >>"Foo" >>and "NewFoo" or "Foo2" sitting right next to it, so we would have to >>think >>of new names for everything. > >I have some POC code for this. It provides a simple toggle at the >start >of the application to select between old style (the default) and new >style >classes. After that, a DeprecationWarning is issued every time an old >style class is defined. The only user visible change is that old style >classes gain an empty old-style base class. The idea being the >old-style/new-style migration could be managed using the usual twisted >deprecation plan. Thoughts?
Process-wide switches are tricky. Some code may decide it wants new- style, while other code wants to stick with classic. They have a fight, one of them loses. I think that adding this is just an invitation for people to create more problems. I think that we should consider requests to make specific classes new- style (and grant them when doing so won't cause compatibility problems), make all new classes new-style, but otherwise leave this alone until 3.x is widely adopted. Jean-Paul _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python
