Re: Subject: [PATCH] * lisp/xwidget.el (xwidget-webkit-browse-url): Remove space prefix of url.

[Eli Zaretskii <eliz@gnu.org>]

> From: Po Lu <luangruo@yahoo.com>
> Cc: tumashu <tumashu@163.com>,  "emacs-devel@gnu.org" <emacs-devel@gnu.org>
> Date: Sat, 13 Nov 2021 09:08:50 +0800
> 
> > But basically tries to guess whether a user is typing in a (possibly
> > incomplete) URL or a search term.
> 
> I'd like to add this:

Is this a replacement for eww--dwim-expand-url?  Or is this in
addition to it?

> (defun url-dwim-expand-url (url local-regex search-prefix)
>   "Canonicalize URL.

First line of a doc string should mention all the mandatory
arguments.  (But see below.)

> Try to determine if URL is an incomplete URL or a search query, and
> return the canonical form of URL.
> SEARCH-PREFIX is the prefix to be prepended to URL if it is a search query.

Can the doc string explain what does "search query" mean in this
context?

> LOCAL-REGEX is a regular expression that URL is matched against.  If the
> match is successful, then URL is treated as an address."

This begs the question: and if it doesn't match, then what?  And what
does "address" mean in this context, i.e. what does "treated as an
address" means in practice?

>   (cond ((string-match-p "\\`file:/" url))
> 	;; Don't mangle file: URLs at all.

This comment should be above the line that handles file:// URLs.
Btw, should other URLs be exempt from "mangling"?  AFAIK, there are
many protocols whose syntax we don't really understand in url*.el
code, so shouldn't they all be left alone?

>         ((string-match-p "\\`ftp://" url)
>          (user-error "FTP is not supported"))

I can understand this in EWW, but why should FTP be unsupported in
url-util?

> 	 ;; Anything that starts with something that vaguely looks
> 	 ;; like a protocol designator is interpreted as a full URL.
>          (if (or (string-match "\\`[A-Za-z]+:" url)

This will match Windows-style d:/foo/bar absolute file names.  Is that
what we want?

> 		 (and (= (length (split-string url)) 1)

You are using split-string here to verify that URL has no SPC
characters?  

> 		      (or (and (not (string-match-p "\\`[\"'].*[\"']\\'" url))
> 			       (> (length (split-string url "[.:]")) 1))

It would be good to have a comment here explaining what do these
conditions test.

> 			  (string-match local-regex url))))

This sole use of LOCAL-REGEX hints that maybe it should be an optional
argument.

>              (progn
>                (unless (string-match-p "\\`[a-zA-Z][-a-zA-Z0-9+.]*://" url)
>                  (setq url (concat "http://" url)))

"http", not "https"?  I think the default nowadays is the latter.

>            (setq url (concat search-prefix
>                              (mapconcat
>                               #'url-hexify-string (split-string url) "+"))))))
>   url)

Doesn't this part mean a search query is expected to be in some
specific format?  If so, that format should be documented in the doc
string.

Thanks.