Smart Incremental Rebuilds With eleventyImport

The Eleventy v2 release improved incremental builds in several ways.

However, a standing issue had been that when you display content from a collection and run an incremental build, that content wouldn't be updated in-sync. You would have to stop an restart your build, or opt back out of incremental local dev.

An additional method was added in v2 to resolve this behavior, and allow you to define which collections can re-build an associated template.

The eleventyImport object can be added via front matter with one child parameter of collections that has an array value. The array should contain the names of any collections you process content from on the page.

The docs for this feature give a post collection as the example:

---
eleventyImport:
  collections: ["post"]
---
<ul>
{%- for post in collections.post -%}
  <li>{{ post.data.title }}</li>
{%- endfor -%}
</ul>

Any content change to a collection template will also trigger rebuild. The rebuild is only of the page that includes the eleventyImport object, and of the template where content was changed.

As noted on the incremental builds docs, rebuild also happens "when you add or delete a tag from a template, any templates using that collection tag... will be rebuilt."

That said, any way you create a collection makes the collection eligible to be included in eleventyImport.

If your blog index resides in your posts folder and you are using a directory data file to assign the collection, then you'll want to exclude the main index from being included in collections:

eleventyExcludeFromCollections: true