regex - find specific text between 2 specified boundary

Question

Hi,

I'm trying to develop a regex that will detect recursive template calls in an xsl style sheet.

So far, it has not been really successful.

In the following code, I need to detect that template B is called recursively:

<xsl:template name="A"> 
     blah blha ?!@#?%$#^%?*?&(({}:"><;'[]\/.,./'
    <xsl:call-template name="B">  
    blah blah      
</xsl:template>    
<xsl:template name="B"> 
   blah blha 
    <xsl:call-template name="B">                
    blah blah  
</xsl:template>
<xsl:template name="C"> 
     blah blha 
    <xsl:call-template name="B">  
    blah blah  
</xsl:template>

In this specific case, the reg ex is ok.

In the case I remove the 2nd call to B, the regex matches the last call to B. That shouldn't happen.

(<xsl:template name=\"(?<templateName>\w+)\">.*?(?<=<xsl:call-template name=\"\k<templateName>\">).*?</xsl:template>)+

I'm no regex guru. Any help is welcome.

Thank you.

Answer 1

Reiterating the obvious point: Don't try parsing XML or other non-regular languages with regular expressions. Please.

Use an XML parser and take a look at the resulting tree. You can create a digraph of the template calls and look for cycles in that. Should be a much more robust solution than trying to hack it together with regular expressions. That way you can also detect that template A might call template B which calls template C and which calls template A again. Such kinds of recursion would be invisible to your current approach (if it could be persuaded to work).