Add post_convert hook to modify HTML content before layout (#8368)

Co-authored-by: John Hughes <johnkhughes@users.noreply.github.com>

docs/_docs/plugins/hooks.md

@@ -129,6 +129,17 @@ The complete list of available hooks is below:
         <p>Just before rendering a page</p>
       </td>
     </tr>
+    <tr>
+      <td>
+        <p><code>:pages</code></p>
+      </td>
+      <td>
+        <p><code>:post_convert</code></p>
+      </td>
+      <td>
+        <p>After converting the page content, but before rendering the page layout</p>
+      </td>
+    </tr>
     <tr>
       <td>
         <p><code>:pages</code></p>
@@ -173,6 +184,17 @@ The complete list of available hooks is below:
         <p>Just before rendering a post</p>
       </td>
     </tr>
+    <tr>
+      <td>
+        <p><code>:posts</code></p>
+      </td>
+      <td>
+        <p><code>:post_convert</code></p>
+      </td>
+      <td>
+        <p>After converting the post content, but before rendering the post layout</p>
+      </td>
+    </tr>
     <tr>
       <td>
         <p><code>:posts</code></p>
@@ -217,6 +239,17 @@ The complete list of available hooks is below:
         <p>Just before rendering a document</p>
       </td>
     </tr>
+    <tr>
+      <td>
+        <p><code>:documents</code></p>
+      </td>
+      <td>
+        <p><code>:post_convert</code></p>
+      </td>
+      <td>
+        <p>After converting the document content, but before rendering the document layout</p>
+      </td>
+    </tr>
     <tr>
       <td>
         <p><code>:documents</code></p>

features/hooks.feature

@@ -103,6 +103,27 @@ Feature: Hooks
     Then I should see "special" in "_site/page1.html"
     And I should not see "special" in "_site/page2.html"
 
+  Scenario: Modify the converted HTML content of a page before rendering layout
+    Given I have a _layouts directory
+    And I have a "_layouts/page.html" file with content:
+    """
+    <h3>Page heading</h3>
+    {{ content }}
+    """
+    And I have a "page.md" page with layout "page" that contains "### Heading"
+    And I have a _plugins directory
+    And I have a "_plugins/ext.rb" file with content:
+    """
+    Jekyll::Hooks.register :pages, :post_convert do |page|
+      page.content = page.content.gsub('h3', 'h4')
+    end
+    """
+    When I run jekyll build
+    Then I should get a zero exit status
+    And the _site directory should exist
+    And I should see "<h3>Page heading</h3>" in "_site/page.html"
+    And I should see "<h4 id=\"heading\">Heading</h4>" in "_site/page.html"
+
   Scenario: Modify page contents before writing to disk
     Given I have a _plugins directory
     And I have a "index.html" page that contains "WRAP ME"
@@ -170,6 +191,34 @@ Feature: Hooks
     Then I should see "old post" in "_site/2015/03/14/entry1.html"
     And I should see "new post" in "_site/2015/03/15/entry2.html"
 
+  Scenario: Modify the converted HTML content of a post before rendering layout
+    Given I have a _layouts directory
+    And I have a "_layouts/post.html" file with content:
+    """
+    <h3>Page heading</h3>
+    {{ content }}
+    """
+    And I have a _posts directory
+    And I have a "_posts/2016-01-01-example.md" file with content:
+    """
+    ---
+    layout: post
+    ---
+    ### Heading
+    """
+    And I have a _plugins directory
+    And I have a "_plugins/ext.rb" file with content:
+    """
+    Jekyll::Hooks.register :posts, :post_convert do |post|
+      post.content = post.content.gsub('h3', 'h4')
+    end
+    """
+    When I run jekyll build
+    Then I should get a zero exit status
+    And the _site directory should exist
+    And I should see "<h3>Page heading</h3>" in "_site/2016/01/01/example.html"
+    And I should see "<h4 id=\"heading\">Heading</h4>" in "_site/2016/01/01/example.html"
+
   Scenario: Modify post contents before writing to disk
     Given I have a _plugins directory
     And I have a "_plugins/ext.rb" file with content:
@@ -278,6 +327,41 @@ Feature: Hooks
     And the _site directory should exist
     And I should see "all your base are belong to us" in "_site/index.html"
 
+  Scenario: Modify the converted HTML content of a document before rendering layout
+    Given I have a _layouts directory
+    And I have a "_layouts/meme.html" file with content:
+    """
+    <h3>Page heading</h3>
+    {{ content }}
+    """
+    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:
+    """
+    ---
+    layout: meme
+    text: all your base
+    ---
+    ### {{ page.text }}
+    """
+    And I have a _plugins directory
+    And I have a "_plugins/ext.rb" file with content:
+    """
+    Jekyll::Hooks.register :documents, :post_convert do |document|
+      document.content = document.content.gsub('h3', 'h4')
+    end
+    """
+    When I run jekyll build
+    Then I should get a zero exit status
+    And the _site directory should exist
+    And I should see "<h3>Page heading</h3>" in "_site/memes/doc1.html"
+    And I should see "<h4 id=\"all-your-base\">all your base</h4>" in "_site/memes/doc1.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:

lib/jekyll/hooks.rb

@@ -22,22 +22,25 @@ module Jekyll
         :post_write  => [],
       },
       :pages     => {
-        :post_init   => [],
+        :post_init    => [],
-        :pre_render  => [],
+        :pre_render   => [],
-        :post_render => [],
+        :post_convert => [],
-        :post_write  => [],
+        :post_render  => [],
+        :post_write   => [],
       },
       :posts     => {
-        :post_init   => [],
+        :post_init    => [],
-        :pre_render  => [],
+        :pre_render   => [],
-        :post_render => [],
+        :post_convert => [],
-        :post_write  => [],
+        :post_render  => [],
+        :post_write   => [],
       },
       :documents => {
-        :post_init   => [],
+        :post_init    => [],
-        :pre_render  => [],
+        :pre_render   => [],
-        :post_render => [],
+        :post_convert => [],
-        :post_write  => [],
+        :post_render  => [],
+        :post_write   => [],
       },
       :clean     => {
         :on_obsolete => [],

lib/jekyll/renderer.rb

@@ -66,7 +66,7 @@ module Jekyll
     # Render the document.
     #
     # Returns String rendered document output
-    # rubocop: disable Metrics/AbcSize
+    # rubocop: disable Metrics/AbcSize, Metrics/MethodLength
     def render_document
       info = {
         :registers        => { :site => site, :page => payload["page"] },
@@ -84,6 +84,10 @@ module Jekyll
       output = convert(output.to_s)
       document.content = output
 
+      Jekyll.logger.debug "Post-Convert Hooks:", document.relative_path
+      document.trigger_hooks(:post_convert)
+      output = document.content
+
       if document.place_in_layout?
         Jekyll.logger.debug "Rendering Layout:", document.relative_path
         output = place_in_layouts(output, payload, info)
@@ -91,7 +95,7 @@ module Jekyll
 
       output
     end
-    # rubocop: enable Metrics/AbcSize
+    # rubocop: enable Metrics/AbcSize, Metrics/MethodLength
 
     # Convert the document using the converters which match this renderer's document.
     #