[Python-Dev] Re: Call for defense of @decorators

["Martin v. Löwis"]

Christian Tismer wrote:
> What I added was yet another __stuff__ entry for new-style
> classes. It may also appear on module level, like the
> __metaclass__ feature works.

While this "works", I still think it is a bad idea, for two
reasons:
1. It only helps the parser, A human reader would have to
    scroll to the top of the class (or worse, to the top of
    the module) to find out.
2. For the author, it is redundant typing - the author *knows*
    this is a decorator, so having to type this again in full
    is redundant.
    1 and 2 together make this a write-only syntax.
3. It means that the parser has to recognize __decorators__
    This is not often the case; I believe the only other
    exception is __future__ (which I also dislike, despite
    its cuteness).
[As any good list of 2 reasons, this list of course has 3]

> But it provides a solution without enforcing us to decide
> about new syntax right now, which appears to be too early
> for a group that can't find a common denominator, yet.

There is a solution already: put the function wrappers after
the declaration. The goal of this change is specifically to
come up with a syntax. If no syntax could be find, it would
be best not to change anything.

I'm not worried that the group cannot agree on syntax:
people can *never* agree on syntax, not just in the case
of Python. If you wait for agreement, you wait forever.

> For my purposes it works fine, but I don't claim that it fulfils
> all other desired use cases. At least it is compatible, simple,
> complete, implemented in a way, and works for my applications.

It's not any more compatbible than the 2.4a2 approach:
- old code (which does not use the feature) continues to work
   correctly (*)
- new code (which uses the feature) won't work on old
   implementations.
(*) Actually, there is a slight incompatibility in your approach:
Code that used to run and used to raise an exception would, under
your change, now suddenly succeed without exception.

Regards,
Martin