11

I am looking for a Regex to match comments in XML documents:

<root>
<!-- 
    match this 
-->
<but>not this</but>
<!--
     and also this
-->
</root>

I've tried <!--[^(-->)]*-->, which only matches single line comments, and <!--[\s\S\n]*--> which matches non-commented nodes as well.

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1 Answer 1

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12

The regex you're looking for would be:

<!--[\s\S\n]*?-->

Explanation:

 <!--               All comments must begin with this
     [\s\S\n]       Any character (. doesn't allow newlines)
             *      0 or more of the previous thing ([\s\S\n])
              ?     As few of the previous thing as possible while still matching
               -->  All comments must end with this

If you have a comment inside a comment this will have issues though:

<!-- Documentation
This program documents itself using comments of the type <!-- -->
-->

Highlighted in bold means a match

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4
  • This exact expression didn't work for me, but this did: <!--[\s\S\n]*?-->. Giving you the green check box for pointing out the "?" though, and the thorough explanation.
    – Dan Solovay
    Dec 5, 2016 at 19:23
  • @DanSolovay I'll edit it to include your discovery of that Visual Studio quirk.
    – timotree
    Dec 5, 2016 at 19:25
  • This will not work if the comment doesn't start at the beginning of line. like: <div> <-- comment -->. The \n is useless in the character class, [\s\S] stands for any character, including newline.
    – Toto
    May 18, 2020 at 10:36
  • @Toto yes... I wrote this answer a while ago and returning to it I am perplexed by it working for 6 people even though it uses ^ and $. Regarding [\s\S\n], see the above comment by the OP saying that adding the \n was necessary for their regex tool.
    – timotree
    May 18, 2020 at 17:16

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