Strange result using ColdFusion custom tag - coldfusion

Question

I created a simple custom tag which takes a string, replaces whitespace with "-" and "&" with "and" for a querystring (I don't want %20's and the like).
Anyways, it works fine, however my custom tag is creating a space before itself like so:
qsEncode.cfm: (custom tag)
<cfparam name="attributes.string" type="string" default="">
<cfset whitespace = Replace(attributes.string," ","-","all")>
<cfset ampersand = Replace(whitespace,"&","and","all")>
<cfoutput>#ampersand#</cfoutput>
The implementation of the tag:
">#getCategory.Name#
And the final output which is creating a space before the tag:
somepage.cfm?Page=%20Finance-and-Taxes
My custom tag isn't being passed a string that has whitespace prepended to it (and even if it was it would be replaced by the "-" character) so I don't understand why the tag is creating whitespace.
Note: I do realize I can include ?Page= inside my custom tag which would fix it, but I'm still curious as to why this is happening.

Answer 1

Your specific problem with extra space can likely be fixed by using:
<cfsetting enablecfoutputonly="true">
as the very first thing inside your custom tag (and setting it back to "false" at the end).
However, I would highly recommend replacing the functionality of the custom tag with an actual function -- either inline, or (preferably) within a cfc. Either way, you want something like this:
<cffunction name="qsEncode" output="false" returntype="string">
<cfargument name="str" type="string" required="true">
<cfset var whitespace = Replace(arguments.str," ","-","all")>
<cfset var ampersand = Replace(whitespace,"&","and","all")>
<cfreturn ampersand>
</cffunction>
Then you'd have:
#getCategory.Name#
For utility functions like these that don't maintain state, a quick solution (putting aside arguments as to the wisdom of singletons) is to set up a utility cfc, and store it as a singleton in the application scope. Instantiate the utility.cfc in the onApplicationStart handler of your Application.cfc. Then, throughout your application, you can do things like this:
application.utility.qsEncode('this');
application.utility.someOtherFunction('that');
application.utility.yetAnotherStringMangler('theother');

Answer 2

Ken is correct - the white space in your custom tag CFM is creating the extra space in it's output. And I recommend his answer (I prefer calling UDF functions in over custom tag CFMs... even better as a function in a CFC object over CFM).
But if you want to simply adjust your existing custom tag, use CFSILENT to stifle whitespace output (and assure no trailing whitespace after last tag in the file).
<cfsilent>
<cfparam name="attributes.string" type="string" default="">
<cfset whitespace = Replace(attributes.string," ","-","all")>
<cfset ampersand = Replace(whitespace,"&","and","all")>
</cfsilent><cfoutput>#ampersand#</cfoutput>