diff --git a/doc/bugs/template_evaluation_oddities.mdwn b/doc/bugs/template_evaluation_oddities.mdwn new file mode 100644 index 000000000..06ef57375 --- /dev/null +++ b/doc/bugs/template_evaluation_oddities.mdwn @@ -0,0 +1,67 @@ +[[ikiwiki/directive/template]]s 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 `\[[!literal """"""]]` because then the `invalid` directive 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 \[[]]! + + would result in a link to 'destination', but would not be registered in the + scan phase and thus not show a backlink from 'foo'. + + (a ``\[[!link to=...]]`` directive, as suggested in + [[todo/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 `raw_` makes +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? + +--[[chrysn]]