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From Ryan Holmes <r...@hyperstep.com>
Subject Re: [T4] If/Else/For tag rendering behavior
Date Mon, 29 Jan 2007 00:54:27 GMT

On Jan 28, 2007, at 3:42 PM, RonPiterman wrote:

> Ryan Holmes wrote:
>> This subject has come up in the past with no real conclusion, but  
>> it did seem like there was consensus on at least one point.  
>> Namely, that an If/Else/For component should automatically emulate  
>> its template tag if the tag is anything other than a span or div  
>> (i.e. tag-dependent rendering/emulation).
> seems like a real strange thing  to me. Either you render a Tag by  
> default or you don't, why exclude span or div? rule like "it makes  
> that unless..." are a good recepie for many postings in this group...
>
> why not just take the 4.1 strategy: use renderTag=true by default?
> Cheers,
> Ron

I'm talking about changing the 4.1 behavior.

This all started with a seemingly harmless suggestion from Howard:  
have If/Else components render their template tags by default unless  
the template tag is a span. Several people (including myself) noted  
that the span exemption should also apply to div tags since divs are  
more or less semantically equivalent (i.e. span and div are both  
generic containers) and are often required to maintain well-formed  
templates.

The reason to even get into this in the first place was to support  
the standard use cases of template tags with If and Else. When you do  
something like <table jwcid="@If" ...> in your template you almost  
always want to render that table tag. When you do <span  
jwcid="@If" ...> you usually want a pure logic component (i.e. you  
don't want to render the span).

While renderTag=true seems like a good idea, it basically just  
reverses the 4.0 behavior without providing real value. In other  
words, where you used to have to add "element=..." to about 50% of  
your If/Else tags you now have to add "renderTag=false" to the other  
50%. This 50/50 ratio bears out over the 160+ page and component  
templates in the 4.0 app my company is working on and I believe Andy  
reported a similar ratio in his templates. The renderTags property  
was added to address the fact that it's just as easy to argue for  
renderTag defaulting to false as it is to argue for the current  
default of true.

It's not hard to imagine that some people will have a 60/40 or 70/30  
split one way or the other in terms of rendering vs. non-rendering If  
and Else components. The only pattern that does seem to exist is that  
you almost always want the If or Else to render when you're using  
something other than span or div in your template, so why not support  
that by default?

renderTag=true actually works out pretty well for For components, at  
least in my experience. But there's a good argument to be made for  
consistent tag rendering behavior across If, Else and For.

My initial reaction to tag-dependent behavior was the same as yours:  
it's too complicated and will confuse beginners. However, the current  
behavior is a compromise that also leads to an "it works like this  
unless..." situation. It depends on the global setting for renderTags  
and whether or not it is overridden for a particular page or  
component, etc. In addition, the renderTags property introduces  
another problem in that the rendering behavior of library components  
that use If/Else/For will change based on your global setting.

I think it would be better to have a simple, consistent rule (even if  
the rule is tag-dependent) rather than forcing a user to figure out  
the implications of changing global behavior. Any potential confusion  
can be mitigated through clear documentation and consistent  
application of the behavior.

By way of comparison, look at the behavior of the Insert component in  
4.0, which will render its template tag if you specify a class  
attribute. This is pretty weird, but I don't recall many questions  
about it because it usually does what you want.

It seems to me there are a couple of basic questions here that we  
could focus on. One is the point that you bring up: is tag-dependent  
rendering simply too confusing to ever consider adding to the  
framework? The other is really a precursor to that: is the assumption/ 
observation that divs and spans usually imply "don't render" while  
other tags usually imply "do render" correct?


-Ryan


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