Fix wrong type hints for SyndicationFeed methods

[WhyNotHugo]

• The correct type is actually mentioned in django's documentation in docs/ref/contrib/syndication.txt.
• The previously defined type doesn't have methods like addQuickElement, which are used in Django's implementation of add_root_elements.

[WhyNotHugo]

I noticed that the exact type of the passed value is django.utils.xmlutils.SimplerXMLGenerator, which is actually a subtype of the documented one. I think that using the documented type is probably safer.

[sobolevn]

@WhyNotHugo can you please point me to the exact place where it is documented? :)

[WhyNotHugo]

I mentioned the source file where this is documented above. The rendered version is at https://docs.djangoproject.com/en/4.2/ref/contrib/syndication/#custom-feed-generators

…

SyndicationFeed.add_root_elements(self, handler) Callback to add elements inside the root feed element (feed/channel). handler is an > XMLGenerator from Python’s built-in SAX library; you’ll call methods on it to add to the > output XML document in process.

[sobolevn]

I cannot find any addQuickElement references in CPython at all 🤔

[WhyNotHugo]

Indeed, addQuickElement is defined in SimplerXMLGenerator in django/utils/xmlutils.py.

My initial version of this fix used SimplerXMLGenerator, but I then switched it to XMLGenerator because the documentation mentions this last one. I guess the docs could be improved here too.

[WhyNotHugo]

I've updated the PR based on this discussion.

[WhyNotHugo]

v3: I've updated a few other methods in this file. No method actually uses ContentHandler here.

[sobolevn]

Thanks! Now it seems to be correct.

[WhyNotHugo]

Is there any way to type-check django's codebase with these type hints? I think doing so would make this kind of inconsistency raise an error pretty quickly.

[sobolevn]

Nope, it is not possible right now.