Why does Jekyll process one collection but not another? - yaml

Question

The problem
I am setting up a Jekyll site which includes collections for categories and authors. I had the categories collection working after some trial & error, now it's broken again but the authors collection works, and I don't understand why. I think something in my configuration is wrong, maybe the _config.yml, but there's no error messages. I could see sometimes when I create a new category (say, _categories/Science), the processor immediately creates a corresponding entry in _site/categories. Categories collection was working perfectly but then something broke, I went back to another commit and now the situation is reversed (author collection works, categories doesn't).
This is my whole _config.yml:
include: ['_categories']
include: ['_authors']
defaults:
-
scope:
path: "" # matches all files in the project
type: posts
values:
layout: "blogLayout"
collections:
category:
output: true
permalink: /categories/:path/
layout: "category"
author:
output: true
permalink: /authors/:slug/
layout: "author"
The collection files are all really simple stubs. This is what a category looks like (_categories/Science.md):
---
layout: category
category-name: Science
permalink: /categories/Science/
---
and here's from the author collection:
---
author: Leo Tolstoy
permalink: /authors/leo-tolstoy/
layout: author
---
My hunch is that it's probably a syntax thing in the _config.yml, either in the YAML syntax or I'm missing up a singular/plural (e.g. authors vs author) someplace but I'm not sure where to look. For completeness sake here's the Front Matter from a post, all of which has worked great until now.
---
layout: blogLayout
title: Anna Karenina excerpt
author: Leo Tolstoy
categories: [testing,Literature]
location: Russia
---
Update (I got it working)
After a bunch of trial & error I eventually got it up and running and figured I would summarize for others who are trying to set up a Jekyll taxonomy.
My final _config.yml file was very simple:
collections:
categories:
output: true
permalink: categories/:path/
authors:
output: true
permalink: authors/:path/
output: true is needed for Jekyll to process that collection. I needed permalinks to be able to go to a directory URL like /categories/dogs/ instead of /categories/dogs.html. It also proved import to NOT have permalinks in any of the collection item files. Live development (serve) mode didn't mind, but when I built the static site it broke a lot of the links until I removed the double permalinks.
The name scheme is that collection items go in _categories/ (or whatever) directory, these don't need much at all. Here is a category file for dogs.md:
---
layout: category
name: Dogs
---
This allowed me to reliably build collections, but searching and viewing a collection took some more work. In this case I had _categories directory to put the dogs.md and such files in. I also needed a categories.html file in the root directory, and a layout called category.html (note the singular vs plural). Here are minimal examples to show what's needed.
categories.html
---
layout: default
title: Categories
---
<h1>Categories</h1>
{% for category in site.categories %}
<h2>{{ category.title }}
</h2>
{% endfor %}
and here is _layouts/category.html:
---
layout: default
---
<h1> {{ page.name }} </h1>
{% assign posts = site.posts | where_exp: "post", "post.categories contains page.name" %}
{% for post in posts %}
<h3>{{ post.title }}</h3>
{% endfor %}
A tricky detail is that other fields types have a field.name property but categories alone have category.title instead.