Coldfusion and unscoped variables - coldfusion

Question

I am currently checking all my functions and components for unscoped variables. I am using a tool called varscoper4 to check all functions. Given the following code varscoper tells me that the variable "input" at line 4 in unscoped. Is this true and do i need to scope the argument variable if I alter it?
<cfoutput>#testit(1)#</cfoutput>
<cffunction name="testit">
<cfargument name="input">
<Cfset input = 3>
<cfreturn input>
</cffunction>
FYI if I do not alter the argument variable input in the function varscoper4 does not report any unscoped variables.
<cfoutput>#testit(1)#</cfoutput>
<cffunction name="testit">
<cfargument name="input">
<Cfset var output = 3 + input>
<cfreturn output>
</cffunction>

Answer 1

In your fist code block, input is "unscoped" but CF interprets it as arguments scope. CF will always try to find your unscoped variables by looking through a priority order. You can find more information on that here: http://www.learncfinaweek.com/week1/Scopes/
You can also view for yourself what that looks like by dumping the different scopes and seeing the output.
<cfoutput>#testit(1)#</cfoutput>
<cffunction name="testit">
<cfargument name="input">
<cfset input = 3>
<cfdump var="#variables#" label="variables">
<cfdump var="#arguments#" label="arguments">
<cfdump var="#local#" label="local">
<cfreturn input>
</cffunction>
I would strongly encourage you to take the output of your varscoper tool as a guide to where you should explicitly scope your variables. In that case, your first block of code would look like this. This is for clarity and certainty in your code.
<cfoutput>#testit(1)#</cfoutput>
<cffunction name="testit">
<cfargument name="input">
<cfset arguments.input = 3>
<cfdump var="#variables#" label="variables">
<cfdump var="#arguments#" label="arguments">
<cfdump var="#local#" label="local">
<cfreturn arguments.input>
</cffunction>
Personally, I don't like setting or changing arguments in my functions and methods. I'd rather keep them unadulterated as you have in your second block of code. But even there, I would explicitly scope the arguments so that you know where it came from -- even if not flagged by varscoper
<cfoutput>#testit(1)#</cfoutput>
<cffunction name="testit">
<cfargument name="input">
<cfset var output = 3 + arguments.input>
<cfdump var="#variables#" label="variables">
<cfdump var="#arguments#" label="arguments">
<cfdump var="#local#" label="local">
<cfreturn output>
</cffunction>
Last thing to be added here if it's not clear is that var scoping puts everything int he local scope. You could also do this and it would be functionally equivalent to the previous block of code:
<cfoutput>#testit(1)#</cfoutput>
<cffunction name="testit">
<cfargument name="input">
<cfset local.output = 3 + arguments.input>
<cfdump var="#variables#" label="variables">
<cfdump var="#arguments#" label="arguments">
<cfdump var="#local#" label="local">
<cfreturn local.output>
</cffunction>

Answer 2

You should use arguments.input:
<cfset arguments.input = 3>
Although even better would be to use your second example, with the arguments scope:
<cfset var output = 3 + arguments.input >
Don't modify arguments, leave them as they are when they arrive, incase you want to re-use the original value later on.
http://help.adobe.com/livedocs/coldfusion/8/htmldocs/help.html?content=buildingComponents_29.html