templates expose odd behavior when it comes to composing links and directives:
the parameters are passed through the preprocessor twice, once on per-parameter basis and once for the final result (which usually contains the preprocessed parameters).
one of the results it that you have to write:
[[!template id="infobox" body=""" Just use the \\\[[!template]] directive! """]]
(that'd be three backslashes in front of the opening [.)
this also means that parts which are not used by the template at all still have their side effects without showing.
furthermore, the evaluation sequence is hard to predict. this might or might not be a problem, depending on whether someone comes up with a less contrived example (this one assumes a
[[!literal value]]directive that just returns value but protects it from the preprocessor):
we can use
[[!literal """[[!invalid example]]"""]], but we can't use
[[!template id=literalator value="""[[!invalid example]]"""]]with a 'literalator' template
<span class="literal">[[!literal """<TMPL_VAR value>"""]]</span>because then the
invaliddirective comes to action in the first (per-argument) preprocessor run
links in templates are not stored at all; they appear, but the backlinks don't work unless the link is explicit in one of the arguments.
[[!template id="linker" destination="foo"]]
with a 'linker' template like
Go to [[<TMPL_VAR destination>]]!
would result in a link to 'destination', but would not be registered in the scan phase and thus not show a backlink from 'foo'.
[[!link to=...]]directive, as suggested in flexible relationships between pages, does get evaluated properly though.)
this seems to be due to linkification being called before preprocess rather than as a part of it, or (if that is on purpose) by the template plugin not running linkification as an extra step (not even once).
(nb: there is a way to include the
raw_ value of a directive, but that only
refers to htmlification, not directive evaluation.)
both those behaviors are non-intuitive and afaict undocumented. personally, i'd
swap them out for passing the parameters as-is to the template, then running
the linkifier and preprocessor on the final result. that would be as if all
parameters were queried
raw_ -- then again, i don't see where
anything not work that worked originally, so obviously i'm missing something.
i think it boils down to one question: are those behaviors necessary for compatibility reasons, and if yes, why?