We do lazy initialization and (potentially) reuse of an output format's rendered content. We do this evaluation when we
start a new rendering a new output format. There are, however, situation where these borders gets crossed (e.g.
accessing content from another output format). We have a check for this in place for most cases, but not the content
rendering of inner markdown blocks inside shortcodes. This patch applies that same logic to the newly introduced
RenderContent method (which is not available from the templates).
Fixes#10391
When a template calls the .Translations function and a
Hugo environment is using multiple output formats,
a template that calls methods like .Summary and .Len on
each translation will unexpectedly show empty return
values for these methods.
This is because each pageOutput's ContentProvider is
assigned to a page.NopPage in newPageOutput. When
*HugoSites.render assigns pageContentOutputs to
pageOutputs in *pageState.shiftToOutputFormat, it
reuses pageContentOutputs from other pageOutputs,
leaving some pageContentOutputs as NopPages. While this
approach conserves resources, sometimes it means that
a template will unexpectedly call a method on a
pageContentOutput that is actually a NopPage.
In the case of ContentProvider methods called on
translations for alternative output formats, the methods
were called on NopPages.
This change introduces LazyContentProvider, which
performs late initialization when one of its methods is
called. This way, we can reuse content in "normal" cases
but ensure that ContentProvider methods work as expected
when a pageOutput is not assigned a pageContentOutput
during the initial pre-render phase.
Fixes#8919
