Jekyll for loop over frontmatter array returning twice

Question

Using Jekyll 3.8.5 (for Github pages).

I have set up a collection _resources, which contains files like this:

---
title: Resource 1
categories:
- title: cat3
  level: 1
- title: cat2
  level: 2
---

I am using a simple Liquid for loop iterate through the categories and their data:

<ul>
        {% for category in resource.categories %}
                <li> Category: {{ category.title }} | Level: {{ category.level }}</li>
        {% endfor %}
    </ul>

The expected result should be:

<ul>
    <li> Category: cat3 | Level: 1</li>
    <li> Category: cat2 | Level: 2</li>
</ul>

Instead, I am getting extra <li> elements:

<ul>
   <li> Category: cat3 | Level: 1</li>
   <li> Category: cat2 | Level: 2</li>
   <li> Category:  | Level: </li>
   <li> Category:  | Level: </li>
</ul>

I checked using {{ categories.size }} and it returned 4

So, I'm sure I'm doing something wrong with my YAML formatting, for Jekyll to think there are two extra categories.

I've tried removing the hyphens in the YAML, but Jekyll throws an error:

no implicit conversion of Hash into Array

Any help very gratefully received.

Thanks,

Mark

Answer 1

tag, tags, category and categories have a special meaning for documents in a collection (posts included).

Jekyll expects a document's tag and category attributes to be simple strings and attributes tags and categories to be simple arrays.

You can try swapping the categories key for something else say foobars.. Then if your updated Liquid loop renders the expected markup, you're all set. Replace foobars with a more appropriate label.

If the issue still occurs, there's something wrong in your layout / include.