Last modified: 2011-08-04 22:21:36 UTC

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Bug 17119 - class Parser: senseless use of non-existing regexp back reference
class Parser: senseless use of non-existing regexp back reference
Product: MediaWiki
Classification: Unclassified
Parser (Other open bugs)
All All
: Low minor (vote)
: ---
Assigned To: Dan Collins
: patch, patch-need-review
Depends on:
  Show dependency treegraph
Reported: 2009-01-22 21:35 UTC by seth
Modified: 2011-08-04 22:21 UTC (History)
1 user (show)

See Also:
Web browser: ---
Mobile Platform: ---
Assignee Huggle Beta Tester: ---

simple patch that applies the suggested change (612 bytes, patch)
2011-08-04 22:16 UTC, Dan Collins

Description seth 2009-01-22 21:35:28 UTC
There's a small error in line
  '/(.) (?=\\?|:|;|!|%|\\302\\273)/' => '\\1 \\2',
in file

$2 (or \2 respectively) is not defined here, because zero-width look-ahead assertions (?=...) are non-capturing patterns.

I suggest one of the following solutions

  '/(.) (\\?|:|;|!|%|\\302\\273)/' => '\\1 \\2',
  '/(.) (?=\\?|:|;|!|%|\\302\\273)/' => '\\1 ',
  '/(?<=.) (?=\\?|:|;|!|%|\\302\\273)/' => ' ',

I don't know which of those is the best. I guess the first one is the slowest.

Btw. for uniformity you could modify the lines
  '/(\\302\\253) /' => '\\1&nbsp;',
  '/&nbsp;(!\s*important)/' => ' \\1', #Beware of CSS magic word !important, bug #11874.
Comment 1 seth 2009-01-22 22:13:25 UTC
1. Oh, &amp;nbsp; is parsed here in bugzilla..., sorry I did not know that.
2. and additional to that you could do a little speed-up by grouping the singe-char alternatives by char classes. So the possible solutions would be

  '/(.) ([?:;!%]|\\302\\273)/' => '\\1&amp;nbsp;\\2',
  '/(.) (?=[?:;!%]|\\302\\273)/' => '\\1&amp;nbsp;',
  '/(?<=.) (?=[?:;!%]|\\302\\273)/' => '&amp;nbsp;',
Comment 2 seth 2009-01-22 22:17:02 UTC
Oops, sorry again, &nbsp; is not parsed, it was just a copy&paste error.
Third try:

A solution would be

  '/(.) ([?:;!%]|\\302\\273)/' => '\\1&nbsp;\\2',
  '/(.) (?=[?:;!%]|\\302\\273)/' => '\\1&nbsp;',
  '/(?<=.) (?=[?:;!%]|\\302\\273)/' => '&nbsp;',
Comment 3 Dan Collins 2011-08-04 22:16:47 UTC
Created attachment 8886 [details]
simple patch that applies the suggested change

Attached patch is incredibly simple and removes the redundant \\2. I checked the rest of Parser.php, there are no other incidences of this bug. This changes no behaviour whatsoever. I tested it anyway and all parsertests still pass.
Comment 4 Dan Collins 2011-08-04 22:21:36 UTC
Fixed in r93925.

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