From: Wes Gamble <weyus@...>
Date: 2006-08-12T08:49:07+09:00
Subject: Re: Crazy gsub/regex scheme - can this be done better?

[ INSANE COMMENT: I just want to say that the black magic that is 
regexes is so   powerful and alluring that I can't resist it and at the 
same time so repulsive that I never want to do it again.  :) :) :) ]

Update - my original scheme would fail when there was an attribute like

content="text/html; charset=UTF-8"

because the latter half would be seen as needing to be charset="UTF-8".

Thus, I became intimate with negative zero-width lookahead.

Here's what I believe to be a more correct solution (I apologize for the 
formatting but I wanted to leave the comments in here).

Wes

#Make sure that every tag attribute is contained within either single or 
double quotes.
  #The initial regex is to find at least one "bad" attribute value pair
  #The "inner" regex is to actually fix ALL of the "bad" attribute value 
pairs
  private
  def ensure_quoted_attributes
    @html.gsub!(/<(?!!)[a-zA-Z0-9]+\s+            #Non-comment tag name, 
followed by whitespace
            (?:[a-zA-Z-]+?=(['"]).*?\1\s*)*?      #Any number of valid 
attribute-value pairs (attribute="value"), not-greedy
            [a-zA-Z-]+?=[^"'\s>]+\s*?             #An unquoted 
attribute-value pair (attribute=value)
             .*?>                                 #Rest of tag
           /mix) { |s|                            #For each tag gotten 
from the first regex, globally substitute into it based on...
                    s.gsub(/(\s+[a-zA-Z-]+=)          #Attribute name
                            (?!(['"])[^'"]*?\2[\s>])  #If the value 
looks like "stuff", then don't match, it's fine
                            (?![^'"]*?['"][\s>])      #If the value 
looks like stuff", then don't match, it must be the tail end of another 
attribute-value pair
                            ([^'"\s>]+)               #Get the 
no-whitespace, no-'>', no quote text
                           /mix) { |sub_s| "#{$1}\"#{$3}\"" } 
#Substitute attribute name="attribute value"
                  }
  end


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