before_flush() sucks

[Mike Bayer]

1. needs a simple "reentrant" blocker so that autoflush on lazyload is blocked throughout the execution of session.flush()

2. the reentrant blocker should raise an error for an explicit userland call to session.flush().

3. the "new", "dirty" and "deleted" lists need to be (re-)calculated after the before_flush() method executes, geez... i.e.

   dirty = self._dirty_states

   ... (check for nothing dirty) ...

   now we're flushing

   flush_context = UOWTransaction(self)

   if self.extension is not None: self.extension.before_flush(self, flush_context, objects)

   # recalculate !
   dirty = self._dirty_states
   

   now get these

   deleted = set(self._deleted) new = set(self._new)

   dirty = set(dirty).difference(deleted)

[Mike Bayer]

1b65c7eed5166d07cc145063f828beeb1d14cf02

[Mike Bayer]

Removing milestone: 0.5.0 (automated comment)