[Python-ideas] decorator syntax limitation

[Haoyi Li]

I've found that a lot of the decorator syntax limitations can be worked
around with an identity decorator:

i = lambda x: x
@i(M(b).decorator())
def wrapped_func():
    pass

kind of ugly, but it works


On Thu, Feb 20, 2014 at 1:31 PM, Franck Michea <franck.michea at gmail.com>wrote:

> Hi there,
>
> Today I hit a limitation of decorator syntax, and I was wondering if
> maybe this limitation could be removed, or if they could allow more.
>
> The grammar for decorators is[1]:
>
>     decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE
>
> But `dotted_name` doesn't allow to write things like the comment put in
> the snippet attached, or this smaller snippet:
>
>     @M(b).decorator()
>     def wrapped_func():
>         pass
>
> Although it looks possible to me to add this syntax, I was wondering
> if it had been discussed previously, and if I could see that
> discussion.
>
> All discussions I found were a lot older, arround the time decorators
> were designed and the syntax was being choosen. I also read PEP306 and
> PEP318.
>
> This is not a blocking issue since you can do with a temporary
> variable, but I was wondering what were your thoughts on this.
>
> Thank you very much,
>
> [1]: http://docs.python.org/3.3/reference/grammar.html
>
> ===== Snippet ==========
> class foo_decorator:
>     def __init__(self):
>         pass
>
>     def __call__(self, func):
>         return func
>
> class Foo:
>     def test(self):
>         return foo_decorator()
>
> class Bar:
>     def __init__(self):
>         self._foo = Foo()
>
> def M(val):
>     return val._foo
>
> b = Bar()
>
> # SyntaxError: @M(b).test()
> m = M(b)
> @m.test()
> def func():
>     print('Hello World!')
>
> func()
> ========================
>
> --
> Franck Michea - EPITA/LSE/GISTRE 2014
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