Use custom classifications (tags, categories, ...)

We used to classify posts with tags & categories.

This patch adds a generic way to define & use your own classifications through `site.config[:classifications]` by adding `tags` like behavior to site & posts for added classifications.

Let's say you want classify Post by referring to Project(s), Customer(s) and Layout(s) you can now simply add the following to `_config.yml` :

```
classifications:
  - projects
  - customers
  - layouts
```

And start using those classifications like you would with `categories` or `tags` :

Add the following to a Post:

```
projects:
  - project1
  - project2
layout:
  - grid
  - responsive
```

And then use the following in any template :

```
<h2>Projects</h2>
<ul>
{% for project in site.projects %}
  <li>{{ project | first }}</li>
{% endfor %}
</ul>
```

jekyll.gemspec

@@ -24,6 +24,7 @@ Gem::Specification.new do |s|
   s.extra_rdoc_files = %w[README.markdown LICENSE]
 
   s.add_runtime_dependency('liquid', "~> 2.5.2")
+  s.add_runtime_dependency('activesupport', "~> 3.2.13")
   s.add_runtime_dependency('classifier', "~> 1.3")
   s.add_runtime_dependency('directory_watcher', "~> 1.4.1")
   s.add_runtime_dependency('maruku', "~> 0.6.0")

lib/jekyll.rb

@@ -26,6 +26,7 @@ def require_all(path)
 require 'liquid'
 require 'maruku'
 require 'colorator'
+require 'active_support/inflector'
 
 # internal requires
 require 'jekyll/core_ext'

lib/jekyll/post.rb

@@ -11,10 +11,8 @@ class Post
       url
       date
       id
-      categories
       next
       previous
-      tags
       path
     ]
 
@@ -34,7 +32,7 @@ def self.valid?(name)
 
     attr_accessor :site
     attr_accessor :data, :extracted_excerpt, :content, :output, :ext
-    attr_accessor :date, :slug, :published, :tags, :categories
+    attr_accessor :date, :slug, :published
 
     attr_reader :name
 
@@ -51,6 +49,10 @@ def initialize(site, source, dir, name)
       @base = self.containing_dir(source, dir)
       @name = name
 
+      @site.classifications.each do |classification|
+        self.class.send :attr_accessor, classification
+      end
+
       self.categories = dir.downcase.split('/').reject { |x| x.empty? }
       self.process(name)
       self.read_yaml(@base, name)
@@ -62,7 +64,7 @@ def initialize(site, source, dir, name)
       self.published = self.published?
 
       self.populate_categories
-      self.populate_tags
+      self.populate_classifications
     end
 
     def published?
@@ -80,8 +82,15 @@ def populate_categories
       self.categories.flatten!
     end
 
-    def populate_tags
-      self.tags = self.data.pluralized_array("tag", "tags").flatten
+    def populate_classifications
+      @site.classifications.each do |classification|
+        next if classification == 'categories'
+        self.send(
+          "#{classification}=".to_sym,
+          self.data.pluralized_array(ActiveSupport::Inflector.singularize(classification), classification).flatten
+        )
+        # => self.tags = self.data.pluralized_array("tag", "tags").flatten
+      end
     end
 
     # Get the full path to the directory containing the post files
@@ -271,6 +280,14 @@ def destination(dest)
       path
     end
 
+    # Convert this post into a Hash for use in Liquid templates.
+    #
+    # Returns the representative Hash.
+    def to_liquid(attrs = nil)
+      classification_data = Hash[@site.classifications.map{ |classification| [classification, send(classification)] }]
+      super(attrs).deep_merge(classification_data)
+    end
+
     # Returns the shorthand String identifier of this Post.
     def inspect
       "<Post: #{self.id}>"

lib/jekyll/site.rb

@@ -1,8 +1,10 @@
 module Jekyll
   class Site
+    FORBIDDEN_CLASSIFICATIONS = %w(posts pages html_pages categories tags).freeze
+
     attr_accessor :config, :layouts, :posts, :pages, :static_files,
-                  :categories, :exclude, :include, :source, :dest, :lsi, :pygments,
-                  :permalink_style, :tags, :time, :future, :safe, :plugins, :limit_posts,
+                  :classifications, :exclude, :include, :source, :dest, :lsi, :pygments,
+                  :permalink_style, :time, :future, :safe, :plugins, :limit_posts,
                   :show_drafts, :keep_files, :baseurl, :data, :file_read_opts
 
     attr_accessor :converters, :generators
@@ -25,6 +27,11 @@ def initialize(config)
       self.file_read_opts = {}
       self.file_read_opts[:encoding] = config['encoding'] if config['encoding']
 
+      self.classifications = %w(categories tags)
+      self.classifications |= (config['classifications'] || []).reject { |c| c !~ /\A[a-z][a-zA-Z_-]*\z/ || FORBIDDEN_CLASSIFICATIONS.include?(c) }
+
+      self.class.send :attr_accessor, *classifications
+
       self.reset
       self.setup
     end
@@ -54,10 +61,12 @@ def reset
       self.posts           = []
       self.pages           = []
       self.static_files    = []
-      self.categories      = Hash.new { |hash, key| hash[key] = [] }
-      self.tags            = Hash.new { |hash, key| hash[key] = [] }
       self.data            = {}
 
+      self.classifications.each do |classification|
+        self.send("#{classification}=".to_sym, Hash.new { |hash, key| hash[key] = [] })
+      end
+
       if self.limit_posts < 0
         raise ArgumentError, "limit_posts must be a non-negative number"
       end
@@ -241,8 +250,9 @@ def render
         page.render(self.layouts, payload)
       end
 
-      self.categories.values.map { |ps| ps.sort! { |a, b| b <=> a } }
-      self.tags.values.map { |ps| ps.sort! { |a, b| b <=> a } }
+      self.classifications.each do |classification|
+        self.send(classification.to_sym).values.map { |ps| ps.sort! { |a, b| b <=> a } }
+      end
     rescue Errno::ENOENT => e
       # ignore missing layout dir
     end
@@ -304,16 +314,20 @@ def site_data
     #                  See Site#post_attr_hash for type info.
     #   "tags"       - The Hash of tag values and Posts.
     #                  See Site#post_attr_hash for type info.
+    # For each custom classification, the Hash will also contain a key:
+    #   "#{classification}" - The Hash of custom classification values and Posts.
     def site_payload
+      site_payload = {
+        "time"       => self.time,
+        "posts"      => self.posts.sort { |a, b| b <=> a },
+        "pages"      => self.pages,
+        "html_pages" => self.pages.reject { |page| !page.html? },
+        "data"       => site_data
+      }
+      self.classifications.each { |key| site_payload[key] = post_attr_hash(key) }
+
       {"jekyll" => { "version" => Jekyll::VERSION },
-       "site" => self.config.merge({
-          "time"       => self.time,
-          "posts"      => self.posts.sort { |a, b| b <=> a },
-          "pages"      => self.pages,
-          "html_pages" => self.pages.reject { |page| !page.html? },
-          "categories" => post_attr_hash('categories'),
-          "tags"       => post_attr_hash('tags'),
-          "data"       => site_data})}
+       "site" => self.config.merge(site_payload)}
     end
 
     # Filter out any files/directories that are hidden or backup files (start
@@ -384,8 +398,9 @@ def get_entries(dir, subfolder)
     # Returns nothing
     def aggregate_post_info(post)
       self.posts << post
-      post.categories.each { |c| self.categories[c] << post }
-      post.tags.each { |c| self.tags[c] << post }
+      self.classifications.each do |classification|
+        post.send(classification.to_sym).each { |c| self.send(classification.to_sym)[c] << post }
+      end
     end
 
     def relative_permalinks_deprecation_method