This also speeds up situations where you only need the fragments/toc and not the rendered content, e.g. Related
with fragments type indexing:
```bash
name old time/op new time/op delta
RelatedSite-10 12.3ms ± 2% 10.7ms ± 1% -12.95% (p=0.029 n=4+4)
name old alloc/op new alloc/op delta
RelatedSite-10 38.6MB ± 0% 38.2MB ± 0% -1.08% (p=0.029 n=4+4)
name old allocs/op new allocs/op delta
RelatedSite-10 117k ± 0% 115k ± 0% -1.36% (p=0.029 n=4+4)
```
Fixes#10750
The main topic of this commit is that you can now index fragments (content heading identifiers) when calling `.Related`.
You can do this by:
* Configure one or more indices with type `fragments`
* The name of those index configurations maps to an (optional) front matter slice with fragment references. This allows you to link
page<->fragment and page<->page.
* This also will index all the fragments (heading identifiers) of the pages.
It's also possible to use type `fragments` indices in shortcode, e.g.:
```
{{ $related := site.RegularPages.Related .Page }}
```
But, and this is important, you need to include the shortcode using the `{{<` delimiter. Not doing so will create infinite loops and timeouts.
This commit also:
* Adds two new methods to Page: Fragments (can also be used to build ToC) and HeadingsFiltered (this is only used in Related Content with
index type `fragments` and `enableFilter` set to true.
* Consolidates all `.Related*` methods into one, which takes either a `Page` or an options map as its only argument.
* Add `context.Context` to all of the content related Page API. Turns out it wasn't strictly needed for this particular feature, but it will
soon become usefil, e.g. in #9339.
Closes#10711
Updates #9339
Updates #10725
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
