Add option to use AND rather than OR for multi-item collections

[Ketrel]

The example in the docs show something like this
content: items: - '@self.children' - '@taxonomy': category: [blog, featured]

It goes on to explain (and in practice I also can confirm) that the behavior is it will show all children from the current page, as well as anything in the blog or featured category.

I'm trying to find a way to do something similar, but show things that match both rather than either, so it would have to be @self.children AND category: [blog,featured].

I can't find any way to do this with the current implementation.

[rhukster]

We plan on implement a much more powerful query language in a future version of Grav to get around limitations in how collections are built. In the meantime, a workaround could be to use two collection defintions, and then merge them:

collection1:
   items: '@self.children'
collection2:
  items:
    - '@taxonomy':
         category: [blog, featured]

Then you merge them:

{% set collection1 = page.collection('collection1') %}
{% set collection2 = page.collection('collection2') %}
{% set collection = collection1.merge(collection2) %}

This will effectively combine the two collections creating an "OR" condition.

[Ketrel]

That's the exact opposite of what I'm asking.

It already does OR if you define multiple items

I'm asking about an AND condition.

[rhukster]

Sorry misread your original issue. This turns out to be a little more complicated and requires some additional logic in Grav (namely a new Collection::intersect() method that can intersect multiple collections. I've added this and its ready for testing in the develop branch.

[rhukster]

Example:

{% set collection1 = page.collection('collection1') %}
{% set collection2 = page.collection('collection2') %}
{% set collection = collection1.intersect(collection2) %}