The wrapt module I linked to (not funtools.wraps) provides all the capabilities you mention since 2013. It allows mixed use of decorators as decorator factories. It has a flat style.There are some minor API difference between your libraries and wrapt, but the concept is very similar. Since yours is something new, I imagine you perceive some win over what wrapt does.On Tue, Mar 12, 2019, 9:52 AM Sylvain MARIE <sylvain.marie@se.com> wrote:David, Steven,
Thanks for your interest !
As you probably know, decorators and function wrappers are *completely different concepts*. A decorator can directly return the decorated function (or class), it does not have to return a wrapper. Even more, it can entirely replace the decorated item with something else (not even a function or class!). Try it: it is possible to write a decorator to replace a function with an integer, even though it is probably not quite useful :)
`decopatch` helps you write decorators, whatever they are. It "just" solves the annoying issue of having to handle the no-parenthesis and with-parenthesis calls. In addition as a 'goodie', it proposes two development styles: *nested* (you have to return a function) and *flat* (you directly write what will happen when the decorator is applied to something).
--
Now about creating signature-preserving function wrappers (in a decorator, or outside a decorator - again, that's not related). That use case is supposed to be covered by functools.wrapt. Unfortunately as explained here https://stackoverflow.com/questions/308999/what-does-functools-wraps-do/55102697#55102697 this is not the case because with functools.wrapt:
- the wrapper code will execute even when the provided arguments are invalid.
- the wrapper code cannot easily access an argument using its name, from the received *args, **kwargs. Indeed one would have to handle all cases (positional, keyword, default) and therefore to use something like Signature.bind().
For this reason I proposed a replacement in `makefun`: https://smarie.github.io/python-makefun/#signature-preserving-function-wrappers
--
Now bridging the gap. Of course a very interesting use cases for decorators is to create decorators that create a signature-preserving wrapper. It is possible to combine decopatch and makefun for this: https://smarie.github.io/python-decopatch/#3-creating-function-wrappers .
Decopatch even proposes a "double-flat" development style where you directly write the wrapper body, as explained in the doc.
Did I answer your questions ?
Thanks again for the quick feedback !
Best,
Sylvain
-----Message d'origine-----
De : Python-ideas <python-ideas-bounces+sylvain.marie=se.com@python.org> De la part de Steven D'Aprano
Envoyé : mardi 12 mars 2019 12:30
À : python-ideas@python.org
Objet : Re: [Python-ideas] Problems (and solutions?) in writing decorators
[External email: Use caution with links and attachments]
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On Tue, Mar 12, 2019 at 09:36:41AM +0000, Sylvain MARIE via Python-ideas wrote:
> I therefore proposed
> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsma
> rie.github.io%2Fpython-makefun%2F&data=02%7C01%7Csylvain.marie%40s
> e.com%7C579232e7e10e475314c708d6a6de9d23%7C6e51e1adc54b4b39b5980ffe9ae
> 68fef%7C0%7C0%7C636879872385158085&sdata=nB9p9V%2BJ7gk%2Fsc%2BA5%2
> Fekk35bnYGvmEFJyCXaLDyLm9I%3D&reserved=0 . In particular it
> provides an equivalent of `@functools.wraps` that is truly
> signature-preserving
Tell us more about that please. I'm very interested in getting decorators preserve the original signature.
--
Steven
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