Subject: libxml-parse-{html,xml}-region help page incorrect argument lower bound

From: Ruijie Yu <[email-masked]>
Date: Fri, 05 May 2023 14:38:02 +0800

First of all, this is newest Emacs 30 in-source build (pulled and built
a few hours ago).

I'm reading the help page of `libxml-parse-xml-region' and noticed this:

--8<---------------cut here---------------start------------->8---
libxml-parse-xml-region is a built-in function in ‘src/xml.c’.

(libxml-parse-xml-region START END &optional BASE-URL)

Parse the region as an XML document and return the parse tree.
If START is nil, it defaults to ‘point-min’.  If END is nil, it
defaults to ‘point-max’.

...
--8<---------------cut here---------------end--------------->8---

Notice the function signature: it implies that the first two arguments
are mandatory, even though the docstring proceeds to talk about what
happens when these two arguments are nil.  Similarly for
`libxml-parse-html-region'.

However, both the C source code and experiments show that these two
functions do accept 0 arguments.

```emacs-lisp
(with-temp-buffer (insert "<html></html>")
                  (libxml-parse-html-region))
;=> (html nil)
```

I have zero knowledge of dealing with C defuns, so I'll leave fixing
this issue to someone more experienced at that.

-- 
Best,

RY

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