[Twisted-web] patch: default values for slots from html templates

[Tommi Virtanen]

Stefano Debenedetti wrote:
> But I like more the syntax suggested by srid for specifying the default:
> + more similar to what other popular templating languages do, XSLT for 
> one but also some java-based I think
> + makes templates more useful when looked at in a browser by themselves 
> (w/o nevow rendering), when testing the l'n'f

The problem with that is that a lot of existing templates already use
<n:slot name="foo">Stuff for the web monkey to see</n:slot>, and you
certainly don't want that to be the default.

Also, I'd imagine it's a valid use case to want to see some "example
data" in the template, when viewed directly, and still set the default
to something else.

<p class="person">
   <n:slot name="fullname" default="MISSING">John Doe</n:slot>
</p>

The biggest downside with the default="foo" syntax is its inability
to do non-strings.

Taking all of the above into consideration, I'd suggest something like

<p class="person">
   <n:slot name="fullname">
     <n:slotdefault>MISSING</n:slotdefault>
     John Doe
   </n:slot>
</p>

and possibly also allow the default="MISSING", to make simple case
simple.