Adding in the ability to link to posts internally. Syntax: {% post_url 2010-07-21-name-of-post %}; useful for: [Some Link]({% post_url 2010-07-21-name-of-post %})

features/create_sites.feature

@@ -92,3 +92,15 @@ Feature: Create sites
     When I debug jekyll
     Then the _site directory should exist
     And I should see "Basic Site with include tag: Generated by Jekyll" in "_site/index.html"
+
+  Scenario: Basic site with internal post linking
+    Given I have an "index.html" page that contains "URL: {% post_url 2020-01-31-entry2 %}"
+    And I have a configuration file with "permalink" set to "pretty"
+    And I have a _posts directory
+    And I have the following posts:
+      | title     | date       | layout  | content                                |
+      | entry1    | 12/31/2007 | post    | content for entry1.                    |
+      | entry2    | 01/31/2020 | post    | content for entry2.                    |
+    When I run jekyll
+    Then the _site directory should exist
+    And I should see "URL: /2020/01/31/entry2/" in "_site/index.html"

lib/jekyll/tags/post_url.rb

@@ -0,0 +1,38 @@
+module Jekyll
+
+  class PostComparer
+    MATCHER = /^(.+\/)*(\d+-\d+-\d+)-(.*)$/
+
+    attr_accessor :date, :slug
+
+    def initialize(name)
+      who, cares, date, slug = *name.match(MATCHER)
+      @slug = slug
+      @date = Time.parse(date)
+    end
+  end
+
+  class PostUrl < Liquid::Tag
+    def initialize(tag_name, post, tokens)
+      super
+      @orig_post = post.strip
+      @post = PostComparer.new(@orig_post)
+    end
+
+    def render(context)
+      site = context.registers[:site]
+      
+      site.posts.each do |p|
+        if p == @post
+          return p.url
+        end
+      end
+
+      puts "ERROR: post_url: \"#{@orig_post}\" could not be found"
+
+      return "#"
+    end
+  end
+end
+
+Liquid::Template.register_tag('post_url', Jekyll::PostUrl)

test/test_tags.rb

@@ -9,6 +9,11 @@ class TestTags < Test::Unit::TestCase
       Jekyll::DEFAULTS.merge({'pygments' => true}).merge(override)
     end
     site = Site.new(Jekyll.configuration)
+
+    if override['read_posts']
+      site.read_posts('')
+    end
+
     info = { :filters => [Jekyll::Filters], :registers => { :site => site } }
     @converter = site.converters.find { |c| c.class == converter_class }
     payload = { "pygments_prefix" => @converter.pygments_prefix,
@@ -137,4 +142,25 @@ CONTENT
       end
     end
   end
+
+  context "simple page with post linking" do
+    setup do
+      content = <<CONTENT
+---
+title: Post linking
+---
+
+{% post_url 2008-11-21-complex %}
+CONTENT
+      create_post(content, {'permalink' => 'pretty', 'source' => source_dir, 'destination' => dest_dir, 'read_posts' => true})
+    end
+
+    should "not cause an error" do
+      assert_no_match /markdown\-html\-error/, @result
+    end
+
+    should "have the url to the \"complex\" post from 2008-11-21" do
+      assert_match %r{/2008/11/21/complex/}, @result
+    end
+  end
 end