Re: Pass through of optional parameters

Wednesday, May 14, 2008, 6:28:58 PM, Daniels, Troy (US SSA) wrote:

>> -----Original Message-----
>> From: [email protected] 
>> [mailto:[email protected]] On 
>> Behalf Of Daniel Dekany
>> Sent: Wednesday, May 14, 2008 4:22 AM
>> To: FreeMarker-user
>> Subject: Re: [FreeMarker-user] Pass through of optional parameters
>> 
>> Wednesday, May 14, 2008, 10:01:00 AM, Attila Szegedi wrote:
>> 
>> > *Sigh*. No, you can't do it, as FreeMarker mandates that all 
>> > expressions used as arguments to a macro invocation resolve to a 
>> > defined value. I wish we'd change that, at least for 
>> optional arguments.
>> >
>> > Jonathan, Daniel - opinions?
>> 
>> I my un-implemented language there is, shown with FTL syntax:
>> 
>>   <@theMacro theParam!noarg>
>> 
>> So, there was special value (special like null is) that means 
>> that the parameter (or list/map item!) is omitted. Overly 
>> smart, one could say... but also quite useful. But it still 
>> doesn't solve that the user has requested in this thread. The 
>> thing is, if you do know that a variable potentially missing, 
>> you have to indicate that in the source code everywhere you 
>> refer to that variable; it has trivial maintainability 
>> related reasons, so I'm reluctant to give it up.
>
> In my case, if I get to a point where I want to use the optional
> variable and it's not there, it's a bug (either in the template or the
> input) and dieing horribly is an acceptable response.

Then it sounds like we agree here. So you don't want
<@foo optionalVariable> to work when the parameter is optional,
right?

>> I don't see 
>> how could it be a reason to relieve this rule that the 
>> variable reference happens to be used as a parameter. Now, in 
>> the case of FreeMarker 2.3, the problem is, that even if the 
>> user accepts this philosophy of strictness, he simply can't 
>> indicate that "I know this variable is possibly missing, and 
>> in that case please consider the whole parameter being 
>> omitted". But starting from FreeMarker 2.4, you can write 
>> theParam?null. 
>
> What's the timeline for 2.4 being released?

It will be released "when it's done"... But I guess late September is
realistic.

>> It's a dirty solution, as it doesn't exactly 
>> behave as if the parameter were omitted, but practically it 
>> will be OK on the quality standard where FreeMarker lives.
>> 
>
> It will certainly work well enough for me.
>
> Troy

-- 
Best regards,
 Daniel Dekany


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