Re: URLs with brackets not recognised

[Maxim Nikulin]

On 13/05/2021 03:06, Rudolf Adamkovič wrote:
> Maxim Nikulin writes:
>
> > I do not think it is a bug. Plain text links detection is a kind of
> > heuristics. It will be always possible to win competition with regexp.
> > Consider it as a limitation requiring some hints from an intelligent
> > user.
>
> I disagree.

Me too. I disagree with most of statements in this thread, even with 
some arguments supposed to support my opinion. Exception is Ihor's 
message. I hope, more liberal regexp will not interfere with parsing of 
other constructs.

Actually I think, you do not realize that detection of URLs in arbitrary 
text is tricky. Maybe you have not noticed corner cases before.

False positives may be even more annoying. At least in the past "smart" 
detection of smiles and emoji in skype transformed code snippets into 
unreadable mess of "glasses of wine" and other "funny" stuff.

> URLs are well-specified. Per RFC 3986,

It describes isolated URI assuming some protocol that allows to 
determine begin and end of URI string. It is impossible to unambiguously 
extract URLs from text written in human languages. Tom pointed that some 
character sequences in URLs can interfere with org markup.

> the characters
> allowed in a URL are [A-Za-z0-9\-._~!$&'()*+,;=:@\/?].

1. Surrounded text may use the same characters. I do not think, you 
would be happy if you got

- <https://orgmode.org/,>
- <https://orgmode.org/worg/org-faq.html)>

from

"(see https://orgmode.org/, https://orgmode.org/worg/org-faq.html)"

just because of "," and ")" characters are allowed in URIs. There is 
just some heuristics that works more or less acceptable in common cases. 
Various implementation have their strong and weak sides.

2. Allowed characters are specified at protocol level. Fortunately in 
user interface most of unicode characters are allowed.

Certainly the following URLs are more portable and reliable
https://el.wikipedia.org/wiki/%CE%9B%CE%AC%CE%BC%CE%B4%CE%B1
https://ja.wikipedia.org/wiki/%E6%97%A5%E6%9C%AC
https://ru.wikipedia.org/wiki/%D0%A1%D1%82%D0%BE%D0%BB%D0%BB%D0%BC%D0%B0%D0%BD,_%D0%A0%D0%B8%D1%87%D0%B0%D1%80%D0%B4_%D0%9C%D1%8D%D1%82%D1%82%D1%8C%D1%8E#%D0%9A%D1%80%D0%B0%D1%82%D0%BA%D0%B0%D1%8F_%D0%B1%D0%B8%D0%BE%D0%B3%D1%80%D0%B0%D1%84%D0%B8%D1%8F
However unicode variants are more informative and readable for humans
https://el.wikipedia.org/wiki/Λάμδα
https://ja.wikipedia.org/wiki/日本
https://ru.wikipedia.org/wiki/Столлман,_Ричард_Мэттью#Краткая_биография

The same is applicable for domain names. Extreme case: 
https://xn--i-7iq.ws/ - https://i❤️.ws/

Even space characters can be used in query part. Modern applications are 
able to convert them to "+" or to "%20" for communication with HTTP servers.

> Org mode should
> implement proper URL detection, not asking its users "to give it some
> hints" and using "a kind of heuristics".

Some tools detect www.google.com as valid URL, others (including org) do 
not. Heuristics can evolve in time. Org render on github can differ from 
elisp original code. Explicit markup is a way to avoid problems.

More complicated regexp makes it harder to support it. (Explaining to 
user that technologies have limitations is a kind of maintenance cost as 
well). Long regexp will have performance penalty and still can be fooled.

Example of link that causes problems even with brackets:
https://lists.gnu.org/archive/html/emacs-orgmode/2020-12/msg00706.html
https://console.aws.amazon.com/cloudwatch/home?region=us-east-1#metricsV2:graph=~(view~'timeSeries~stacked~false~metrics~(~(~'CWAgent~'backup_time~'host~'desktop~'metric_type~'timing))~region~'us-east-1);query=~'*7bCWAgent*2chost*2cmetric_type*7d

On 12/05/2021 23:44, Colin Baxter wrote:
> It might be worthwhile to issue an warning each time a url is written in
> an org file without enclosing brackets < > or [[ ]].

Simple links works well. I am afraid that detecting, whether a 
particular link is a corner case that needs brackets, may require more 
complicated logic than regexp detecting links.

On 13/05/2021 09:21, Tim Cross wrote:
> As this is defined and documented behaviour,

My impression that nuances of recognition of plain text links are not 
documented. Even unit tests exists only in the proposed patch. Actually 
I do not think that such details are necessary in the manual. 
Fontification provides feedback. As soon as problems noticed, explicit 
marks can be added.

On 13/05/2021 05:23, Tom Gillespie wrote:
> A quick fix is to percent encode the troublesome characters

org-lint does not like percent encoding in links. It is heritage of a 
period when *extra* pass of percent encoding was used to escape square 
brackets and spaces. Current recommendation is to escape only brackets 
and backslashes leaving spaces as is (however org-fill-paragraph 
believes that it has full rights to do something with spaces).

Personally I do not see why adding angle or double square brackets is a 
problem. While approaching limits, it is better to stay on the safe 
side. Particular case initiated this topic can be solved but more 
complicated URLs will arise. Just admit that preparing of documents 
requires some collaboration and assistance from users to make intentions 
more explicit.