Using the ApiSandbox:

http://en.wikipedia.org/wiki/Special:ApiSandbox#action=expandtemplates&format=json&text=%7B%7BUser%3AVolker.haas%2FTemplateExpansion%7D%7D

The result shows up {{cite web... I guess there is no recursion.

With action=parse&prop=text&page=User:Voker.haas/TemplateExpansion

http://en.wikipedia.org/wiki/Special:ApiSandbox#action=parse&format=json&page=User%3AVolker.haas%2FTemplateExpansion&prop=text

So I guess you want to use action=parse&prop=text&page= instead of action=expandtemplate.

ralf_wikimedia wrote:

Does the above call expand templates and give me mediawiki markup? If not, that's not what we want...

Ah no, that render them :-] Sorry.

Compare this with the behavior described on T30616: Special:ExpandTemplates - Preview seems to be parsed twice.

(In reply to comment #5)

Compare this with the behavior described on bug 28616.

http://de.wikipedia.org/w/api.php?action=expandtemplates&format=jsonfm&text=%7B%7B((%7D%7DVorlage%7B%7B!%7D%7DX%7B%7B))%7D%7D%20%3Cp%3Cincludeonly%2F%3Ere%3EX%3C%2Fpre%3E

The problem is that "expandtemplates" is a bit of a hack: it half-parses the wikitext to get new wikitext. But this half-parsing can't include calling tag hooks, because the tag hook returns HTML rather than wikitext. And it can't necessarily parse the text passed to the tag hook, because the tag hook might do almost anything with it (e.g. <syntaxhighlight> doesn't expand any templates, <ref> does, and it's theoretically possible to create a tag hook that would run inline Lua code or the like. So it just outputs the tag contents as-is.

It sometimes breaks in other ways, too. Consider, for example, what it does to something like "{{#tag:ref|Ref A<ref>Ref B</ref>}}".

Bug 28616 is similar: Special:ExpandTemplates half-parses the wikitext, and then parsed the half-parsed wikitext. This two-step parse can give different results.

ralf_wikimedia wrote:

*** Bug 50090 has been marked as a duplicate of this bug. ***

ralf_wikimedia wrote:

*** Bug 48872 has been marked as a duplicate of this bug. ***

• Bug 53260 has been marked as a duplicate of this bug. ***

Is this really still high priority (priority not changed for two years) now that PDF rendering is done by OCG?

The merged and blocked tasks have been solved by the introduction of the new PDF generation system last year.

Either this task is solved too, or they have to be unmerged

Not specific to the API (unsurprisingly, since it is a parser issue), the same problem occurs with action=raw&templates=expand.

In T48115#486504, @Anomie wrote:

The problem is that "expandtemplates" is a bit of a hack: it half-parses the wikitext to get new wikitext. But this half-parsing can't include calling tag hooks, because the tag hook returns HTML rather than wikitext. And it can't necessarily parse the text passed to the tag hook, because the tag hook might do almost anything with it (e.g. <syntaxhighlight> doesn't expand any templates, <ref> does, and it's theoretically possible to create a tag hook that would run inline Lua code or the like. So it just outputs the tag contents as-is.

It sometimes breaks in other ways, too. Consider, for example, what it does to something like "{{#tag:ref|Ref A<ref>Ref B</ref>}}".

Bug 28616 is similar: Special:ExpandTemplates half-parses the wikitext, and then parsed the half-parsed wikitext. This two-step parse can give different results.

It's worse than that. Templates, under normal circumstances, shouldn't be expanded in <nowiki> tags (obviously). But, if those nowiki tags are passed as an argument to [[Module:Preprocess]] on enwiki, or some other module that does something similar, then the templates do need to be expanded.