Parenthesis `(` / `)` in URLs causes unintended duplicate links

[netweb]

In the support forums, if you use this:

• <a href="https://msdn.microsoft.com/en-us/library/ms530820(v=vs.85).aspx" target="_blank">https://msdn.microsoft.com/en-us/library/ms530820(v=vs.85).aspx</a>

It escapes to this:

• <a href="https://msdn.microsoft.com/en-us/library/ms530820(v=vs.85).aspx" target="_blank" rel="nofollow"></a><a href="https://msdn.microsoft.com/en-us/library/ms530820(v=vs.85)" rel="nofollow">https://msdn.microsoft.com/en-us/library/ms530820(v=vs.85)</a>.aspx

Originall reported by @cybr in Slack #meta ​https://wordpress.slack.com/archives/C02QB8GMM/p1495374031432056

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A standard WordPress post results in the correct formatting:

• <a href="https://msdn.microsoft.com/en-us/library/ms530820(v=vs.85).aspx" target="_blank">https://msdn.microsoft.com/en-us/library/ms530820(v=vs.85).aspx</a>

When looking closer bbPress in fact is turning it into two links:

• <a href="https://msdn.microsoft.com/en-us/library/ms530820(v=vs.85).aspx" target="_blank" rel="nofollow"></a>

• and

• <a href="https://msdn.microsoft.com/en-us/library/ms530820(v=vs.85)" rel="nofollow">https://msdn.microsoft.com/en-us/library/ms530820(v=vs.85)</a>.aspx

I suspect the parenthesis might be getting tripped up in bbp_make_clickable()

[johnjamesjacoby]

WordPress uses make_clickable() in comments, and exhibits the same problem.

This will be tricky, because parenthesis are used to roll/unroll the crazy-fun regular expression.

I'll look at it here, but it'll require an upstream patch to WordPress, too.

[johnjamesjacoby]

The bug happens because of assumptions regarding what a URL with parenthesis looks like:

• Must have matching pairs of ( and ) which seems sane, but might not be part of any official spec
• Must not have trailing text after the final parenthesis pair (like .html in this case)

The second assumption is part of ​#WP14993, likely thanks to how many Wikipedia URLs are structured.

I'm going to punt this to Future Release here because this will require an upstream change to _make_url_clickable_cb() which bbPress does still use, even though it has its own bbp_make_clickable function & filter pair.