Pandoc not converting mediawiki links with empty query parameter value properly

[outofcontrol]

Version: pandoc 2.0.1.1 - 2.0.2 (possibly more)

Bug: Repeatable: Pandoc gets confused when trying to convert a URL that has empty parameters in it.

This bug is revealed when converting from Mediawiki to Github Flavoured Markdown (gfm). To demonstrate this bug, use the online Pandoc converter. Using this sample:

[https://domain.com/script.php?a=1&b=2&c=&d=4 open productname bugs]

The result should be:

[open productname bugs](https://domain.com/script.php?a=1&b=2&c=&d=4)

Instead, Pandoc gets confused when a parameter is empty (...c=&d...) and results in this:

\[<https://domain.com/script.php?a=1&b=2&c>=\&d=4 open productname bugs\]

[mb21]

There's indeed a bug there, but the problem is the &c= which isn't followed by a value. Minimal example:

$ echo '[http://domain.com?a= open productname bugs]' | pandoc -f mediawiki
<p>[<a href="http://domain.com?a" class="uri">http://domain.com?a</a>= open productname bugs]</p>

[mb21]

This should probably be fixed in uri.

> runParser uri () "" "http://domain.com?a=&b=1"
Right ("http://domain.com?a","http://domain.com?a")

[outofcontrol]

In the same vain as the above issue, this is another link which break pandoc: conversion from Mediawiki to other formats:

[http://domain.com?a=. open productname bugs]

Perhaps others.

[jgm]

The uri parser has a heuristic designed for excluding punctuation that follows bare URIs in text.
This should definitely be refined to give better results for the examples above.