Refine hook implementation

- hooks are registered to symbol owners rather than classes directly
- during registration, add the ability to specify owner as an array to
  register the same hook to multiple owners
- add optional priority during registration as a symbol (:low, :normal,
  :high)
- implement hooks for collections as they are in octopress-hooks, aside
  from post_init

features/hooks.feature

@@ -6,7 +6,7 @@ Feature: Hooks
     Given I have a _plugins directory
     And I have a "_plugins/ext.rb" file with content:
     """
-    Jekyll::Hooks.register Jekyll::Site, :reset do |site|
+    Jekyll::Hooks.register :site, :reset do |site|
       pageklass = Class.new(Jekyll::Page) do
         def initialize(site, base)
           @site = site
@@ -32,7 +32,7 @@ Feature: Hooks
     And I have a "index.html" page that contains "{{ site.injected }}!"
     And I have a "_plugins/ext.rb" file with content:
     """
-    Jekyll::Hooks.register Jekyll::Site, :pre_render do |site, payload|
+    Jekyll::Hooks.register :site, :pre_render do |site, payload|
       payload['site']['injected'] = 'myparam'
     end
     """
@@ -46,7 +46,7 @@ Feature: Hooks
     And I have a "page2.html" page that contains "page2"
     And I have a "_plugins/ext.rb" file with content:
     """
-    Jekyll::Hooks.register Jekyll::Site, :post_read do |site|
+    Jekyll::Hooks.register :site, :post_read do |site|
       site.pages.delete_if { |p| p.name == 'page1.html' }
     end
     """
@@ -59,7 +59,7 @@ Feature: Hooks
     Given I have a _plugins directory
     And I have a "_plugins/ext.rb" file with content:
     """
-    Jekyll::Hooks.register Jekyll::Site, :post_write do |site|
+    Jekyll::Hooks.register :site, :post_write do |site|
       firstpage = site.pages.first
       content = File.read firstpage.destination(site.dest)
       File.write(File.join(site.dest, 'firstpage.html'), content)
@@ -74,7 +74,7 @@ Feature: Hooks
     Given I have a _plugins directory
     And I have a "_plugins/ext.rb" file with content:
     """
-    Jekyll::Hooks.register Jekyll::Page, :post_init do |page|
+    Jekyll::Hooks.register :page, :post_init do |page|
       page.name = 'renamed.html'
       page.process(page.name)
     end
@@ -88,7 +88,7 @@ Feature: Hooks
     Given I have a _plugins directory
     And I have a "_plugins/ext.rb" file with content:
     """
-    Jekyll::Hooks.register Jekyll::Page, :pre_render do |page, payload|
+    Jekyll::Hooks.register :page, :pre_render do |page, payload|
       payload['myparam'] = 'special' if page.name == 'page1.html'
     end
     """
@@ -103,7 +103,7 @@ Feature: Hooks
     And I have a "index.html" page that contains "WRAP ME"
     And I have a "_plugins/ext.rb" file with content:
     """
-    Jekyll::Hooks.register Jekyll::Page, :post_render do |page|
+    Jekyll::Hooks.register :page, :post_render do |page|
       page.output = "{{{{{ #{page.output.chomp} }}}}}"
     end
     """
@@ -115,7 +115,7 @@ Feature: Hooks
     And I have a "index.html" page that contains "HELLO FROM A PAGE"
     And I have a "_plugins/ext.rb" file with content:
     """
-    Jekyll::Hooks.register Jekyll::Page, :post_write do |page|
+    Jekyll::Hooks.register :page, :post_write do |page|
       require 'fileutils'
       filename = page.destination(page.site.dest)
       FileUtils.mv(filename, "#{filename}.moved")
@@ -129,7 +129,7 @@ Feature: Hooks
     And I have a "_plugins/ext.rb" file with content:
     """
     # rot13 translate
-    Jekyll::Hooks.register Jekyll::Post, :post_init do |post|
+    Jekyll::Hooks.register :post, :post_init do |post|
       post.content.tr!('abcdefghijklmnopqrstuvwxyz',
         'nopqrstuvwxyzabcdefghijklm')
     end
@@ -148,7 +148,7 @@ Feature: Hooks
     """
     # Add myvar = 'old' to posts before 2015-03-15, and myvar = 'new' for
     # others
-    Jekyll::Hooks.register Jekyll::Post, :pre_render do |post, payload|
+    Jekyll::Hooks.register :post, :pre_render do |post, payload|
       if post.date < Time.new(2015, 3, 15)
         payload['myvar'] = 'old'
       else
@@ -170,7 +170,7 @@ Feature: Hooks
     And I have a "_plugins/ext.rb" file with content:
     """
     # Replace content after rendering
-    Jekyll::Hooks.register Jekyll::Post, :post_render do |post|
+    Jekyll::Hooks.register :post, :post_render do |post|
       post.output.gsub! /42/, 'the answer to life, the universe and everything'
     end
     """
@@ -188,7 +188,7 @@ Feature: Hooks
     And I have a "_plugins/ext.rb" file with content:
     """
     # Log all post filesystem writes
-    Jekyll::Hooks.register Jekyll::Post, :post_write do |post|
+    Jekyll::Hooks.register :post, :post_write do |post|
       filename = post.destination(post.site.dest)
       open('_site/post-build.log', 'a') do |f|
         f.puts "Wrote #{filename} at #{Time.now}"
@@ -203,3 +203,125 @@ Feature: Hooks
     When I run jekyll build
     Then I should see "_site/2015/03/14/entry1.html at" in "_site/post-build.log"
     Then I should see "_site/2015/03/15/entry2.html at" in "_site/post-build.log"
+
+  Scenario: Register a hook on multiple owners at the same time
+    Given I have a _plugins directory
+    And I have a "_plugins/ext.rb" file with content:
+    """
+    Jekyll::Hooks.register [:page, :post], :post_render do |owner|
+      owner.output = "{{{{{ #{owner.output.chomp} }}}}}"
+    end
+    """
+    And I have a "index.html" page that contains "WRAP ME"
+    And I have a _posts directory
+    And I have the following posts:
+      | title  | date       | layout | content   |
+      | entry1 | 2015-03-14 | nil    | entry one |
+    When I run jekyll build
+    Then I should see "{{{{{ WRAP ME }}}}}" in "_site/index.html"
+    And I should see "{{{{{ <p>entry one</p> }}}}}" in "_site/2015/03/14/entry1.html"
+
+  Scenario: Allow hooks to have a named priority
+    Given I have a _plugins directory
+    And I have a "_plugins/ext.rb" file with content:
+    """
+    Jekyll::Hooks.register :page, :post_render, priority: :normal do |owner|
+      # first normal runs second
+      owner.output = "1 #{owner.output.chomp}"
+    end
+    Jekyll::Hooks.register :page, :post_render, priority: :high do |owner|
+      # high runs last
+      owner.output = "2 #{owner.output.chomp}"
+    end
+    Jekyll::Hooks.register :page, :post_render do |owner|
+      # second normal runs third (normal is default)
+      owner.output = "3 #{owner.output.chomp}"
+    end
+    Jekyll::Hooks.register :page, :post_render, priority: :low do |owner|
+      # low runs first
+      owner.output = "4 #{owner.output.chomp}"
+    end
+    """
+    And I have a "index.html" page that contains "WRAP ME"
+    When I run jekyll build
+    Then I should see "2 3 1 4 WRAP ME" in "_site/index.html"
+
+  Scenario: Alter a document right after it is initialized
+    Given I have a _plugins directory
+    And I have a "_plugins/ext.rb" file with content:
+    """
+    Jekyll::Hooks.register :document, :pre_render do |doc, payload|
+      doc.data['text'] = doc.data['text'] << ' are belong to us'
+    end
+    """
+    And I have a "_config.yml" file that contains "collections: [ memes ]"
+    And I have a _memes directory
+    And I have a "_memes/doc1.md" file with content:
+    """
+    ---
+    text: all your base
+    ---
+    """
+    And I have an "index.md" file with content:
+    """
+    ---
+    ---
+    {{ site.memes.first.text }}
+    """
+    When I run jekyll build
+    Then the _site directory should exist
+    And I should see "all your base are belong to us" in "_site/index.html"
+
+  Scenario: Update a document after rendering it, but before writing it to disk
+    Given I have a _plugins directory
+    And I have a "_plugins/ext.rb" file with content:
+    """
+    Jekyll::Hooks.register :document, :post_render do |doc|
+      doc.output.gsub! /<p>/, '<p class="meme">'
+    end
+    """
+    And I have a "_config.yml" file with content:
+    """
+    collections:
+      memes:
+        output: true
+    """
+    And I have a _memes directory
+    And I have a "_memes/doc1.md" file with content:
+    """
+    ---
+    text: all your base are belong to us
+    ---
+    {{ page.text }}
+    """
+    When I run jekyll build
+    Then the _site directory should exist
+    And I should see "<p class=\"meme\">all your base are belong to us" in "_site/memes/doc1.html"
+
+  Scenario: Perform an action after every document is written
+    Given I have a _plugins directory
+    And I have a "_plugins/ext.rb" file with content:
+    """
+    Jekyll::Hooks.register :document, :post_write do |doc|
+      open('_site/document-build.log', 'a') do |f|
+        f.puts "Wrote document #{doc.collection.docs.index doc} at #{Time.now}"
+      end
+    end
+    """
+    And I have a "_config.yml" file with content:
+    """
+    collections:
+      memes:
+        output: true
+    """
+    And I have a _memes directory
+    And I have a "_memes/doc1.md" file with content:
+    """
+    ---
+    text: all your base are belong to us
+    ---
+    {{ page.text }}
+    """
+    When I run jekyll build
+    Then the _site directory should exist
+    And I should see "Wrote document 0" in "_site/document-build.log"

lib/jekyll/document.rb

@@ -175,11 +175,15 @@ module Jekyll
     #
     # Returns nothing.
     def write(dest)
+      Jekyll::Hooks.trigger self, :post_render
+
       path = destination(dest)
       FileUtils.mkdir_p(File.dirname(path))
       File.open(path, 'wb') do |f|
         f.write(output)
       end
+
+      Jekyll::Hooks.trigger self, :post_write
     end
 
     # Returns merged option hash for File.read of self.site (if exists)

lib/jekyll/hooks.rb

@@ -1,51 +1,101 @@
 module Jekyll
   module Hooks
+    # Helps look up hooks from the registry by owner's class
+    OWNER_MAP = {
+      Jekyll::Site => :site,
+      Jekyll::Page => :page,
+      Jekyll::Post => :post,
+      Jekyll::Document => :document,
+    }.freeze
+
+    DEFAULT_PRIORITY = 20
+
+    # compatibility layer for octopress-hooks users
+    PRIORITY_MAP = {
+      low: 10,
+      normal: 20,
+      high: 30,
+    }.freeze
+
     # initial empty hooks
     @registry = {
-      Jekyll::Site => {
+      :site => {
         reset: [],
         post_read: [],
         pre_render: [],
         post_write: [],
       },
-      Jekyll::Page => {
+      :page => {
         post_init: [],
         pre_render: [],
         post_render: [],
         post_write: [],
       },
-      Jekyll::Post => {
+      :post => {
         post_init: [],
         pre_render: [],
         post_render: [],
         post_write: [],
       },
+      :document => {
+        pre_render: [],
+        post_render: [],
+        post_write: [],
+      },
     }
 
+    # map of all hooks and their priorities
+    @hook_priority = {}
+
     NotAvailable = Class.new(RuntimeError)
 
-    # register a hook to be called later
-    def self.register(klass, event, &block)
-      unless @registry[klass]
+    # register hook(s) to be called later
+    def self.register(owners, event, priority: nil, &block)
+      Array(owners).each do |owner|
+        register_one(owner, event, priority: priority_value(priority), &block)
+      end
+    end
+
+    # Ensure the priority is a Fixnum
+    def self.priority_value(priority=nil)
+      return DEFAULT_PRIORITY unless priority
+      return priority if priority.is_a?(Fixnum)
+      PRIORITY_MAP[priority] || DEFAULT_PRIORITY
+    end
+
+    # register a single hook to be called later
+    def self.register_one(owner, event, priority: nil, &block)
+      unless @registry[owner]
         raise NotAvailable, "Hooks are only available for the following " <<
           "classes: #{@registry.keys.inspect}"
       end
 
-      unless @registry[klass][event]
-        raise NotAvailable, "Invalid hook. #{klass} supports only the " <<
-          "following hooks #{@registry[klass].keys.inspect}"
+      unless @registry[owner][event]
+        raise NotAvailable, "Invalid hook. #{owner} supports only the " <<
+          "following hooks #{@registry[owner].keys.inspect}"
       end
 
-      @registry[klass][event] << block
+      insert_hook owner, event, priority, &block
+    end
+
+    def self.insert_hook(owner, event, priority, &block)
+      @hook_priority[block] = "#{priority}.#{@hook_priority.size}".to_f
+      @registry[owner][event] << block
     end
 
     # interface for Jekyll core components to trigger hooks
     def self.trigger(instance, event, *args)
-      # proceed only if there are hooks to call
-      return unless @registry[instance.class]
-      return unless @registry[instance.class][event]
+      owner_symbol = OWNER_MAP[instance.class]
 
-      @registry[instance.class][event].each do |hook|
+      # proceed only if there are hooks to call
+      return unless @registry[owner_symbol]
+      return unless @registry[owner_symbol][event]
+
+      # hooks to call for this owner and event
+      hooks = @registry[owner_symbol][event]
+
+      # sort and call hooks according to priority and load order
+      hooks.sort_by { |h| @hook_priority[h] }.each do |hook|
         hook.call(instance, *args)
       end
     end

site/_docs/plugins.md

@@ -491,16 +491,16 @@ custom functionality every time Jekyll renders a post, you could register a
 hook like this:
 
 {% highlight ruby %}
-Jekyll::Hooks.register Jekyll::Post, :post_render do |post|
+Jekyll::Hooks.register :post, :post_render do |post|
   # code to call after Jekyll renders a post
 end
 {% endhighlight %}
 
-Jekyll provides hooks for <code>Jekyll::Site</code>, <code>Jekyll::Page</code>
-and <code>Jekyll::Post</code>. In all cases, Jekyll calls your hooks with the
-container object as the first callback parameter. But in the case of
-<code>:pre_render</code>, your hook will also receive a payload hash as a
-second parameter which allows you full control over the variables that are
+Jekyll provides hooks for <code>:site</code>, <code>:page</code>,
+<code>:post</code>, and <code>:document</code>. In all cases, Jekyll calls your
+hooks with the container object as the first callback parameter. But in the
+case of <code>:pre_render</code>, your hook will also receive a payload hash as
+a second parameter which allows you full control over the variables that are
 available while rendering.
 
 The complete list of available hooks is below:
@@ -517,7 +517,7 @@ The complete list of available hooks is below:
   <tbody>
     <tr>
       <td>
-        <p><code>Jekyll::Site</code></p>
+        <p><code>:site</code></p>
       </td>
       <td>
         <p><code>:reset</code></p>
@@ -528,7 +528,7 @@ The complete list of available hooks is below:
     </tr>
     <tr>
       <td>
-        <p><code>Jekyll::Site</code></p>
+        <p><code>:site</code></p>
       </td>
       <td>
         <p><code>:pre_render</code></p>
@@ -539,7 +539,7 @@ The complete list of available hooks is below:
     </tr>
     <tr>
       <td>
-        <p><code>Jekyll::Site</code></p>
+        <p><code>:site</code></p>
       </td>
       <td>
         <p><code>:post_render</code></p>
@@ -550,7 +550,7 @@ The complete list of available hooks is below:
     </tr>
     <tr>
       <td>
-        <p><code>Jekyll::Site</code></p>
+        <p><code>:site</code></p>
       </td>
       <td>
         <p><code>:post_write</code></p>
@@ -561,7 +561,7 @@ The complete list of available hooks is below:
     </tr>
     <tr>
       <td>
-        <p><code>Jekyll::Page</code></p>
+        <p><code>:page</code></p>
       </td>
       <td>
         <p><code>:post_init</code></p>
@@ -572,7 +572,7 @@ The complete list of available hooks is below:
     </tr>
     <tr>
       <td>
-        <p><code>Jekyll::Page</code></p>
+        <p><code>:page</code></p>
       </td>
       <td>
         <p><code>:pre_render</code></p>
@@ -583,7 +583,7 @@ The complete list of available hooks is below:
     </tr>
     <tr>
       <td>
-        <p><code>Jekyll::Page</code></p>
+        <p><code>:page</code></p>
       </td>
       <td>
         <p><code>:post_render</code></p>
@@ -594,7 +594,7 @@ The complete list of available hooks is below:
     </tr>
     <tr>
       <td>
-        <p><code>Jekyll::Page</code></p>
+        <p><code>:page</code></p>
       </td>
       <td>
         <p><code>:post_write</code></p>
@@ -605,7 +605,7 @@ The complete list of available hooks is below:
     </tr>
     <tr>
       <td>
-        <p><code>Jekyll::Post</code></p>
+        <p><code>:post</code></p>
       </td>
       <td>
         <p><code>:post_init</code></p>
@@ -616,7 +616,7 @@ The complete list of available hooks is below:
     </tr>
     <tr>
       <td>
-        <p><code>Jekyll::Post</code></p>
+        <p><code>:post</code></p>
       </td>
       <td>
         <p><code>:pre_render</code></p>
@@ -627,7 +627,7 @@ The complete list of available hooks is below:
     </tr>
     <tr>
       <td>
-        <p><code>Jekyll::Post</code></p>
+        <p><code>:post</code></p>
       </td>
       <td>
         <p><code>:post_render</code></p>
@@ -638,7 +638,7 @@ The complete list of available hooks is below:
     </tr>
     <tr>
       <td>
-        <p><code>Jekyll::Post</code></p>
+        <p><code>:post</code></p>
       </td>
       <td>
         <p><code>:post_write</code></p>
@@ -647,6 +647,39 @@ The complete list of available hooks is below:
         <p>After writing a post to disk</p>
       </td>
     </tr>
+    <tr>
+      <td>
+        <p><code>:document</code></p>
+      </td>
+      <td>
+        <p><code>:pre_render</code></p>
+      </td>
+      <td>
+        <p>Just before rendering a document</p>
+      </td>
+    </tr>
+    <tr>
+      <td>
+        <p><code>:document</code></p>
+      </td>
+      <td>
+        <p><code>:post_render</code></p>
+      </td>
+      <td>
+        <p>After rendering a document, but before writing it to disk</p>
+      </td>
+    </tr>
+    <tr>
+      <td>
+        <p><code>:document</code></p>
+      </td>
+      <td>
+        <p><code>:post_write</code></p>
+      </td>
+      <td>
+        <p>After writing a document to disk</p>
+      </td>
+    </tr>
   </tbody>
 </table>
 </div>