Add Inline Markdown converter

.rubocop.yml

@@ -39,6 +39,8 @@ Metrics/MethodLength:
   Max: 20
   Severity: error
 Metrics/ModuleLength:
+  Exclude:
+    - lib/jekyll/filters.rb
   Max: 240
 Metrics/ParameterLists:
   Max: 4

features/embed_filters.feature

@@ -63,6 +63,18 @@ Feature: Embed filters
     And the _site directory should exist
     And I should see "By <p><em>Obi-wan</em></p>" in "_site/2009/03/27/star-wars.html"
 
+  Scenario: Markdownify a given inline string
+    Given I have a _posts directory
+    And I have a _layouts directory
+    And I have the following post:
+      | title     | date       | layout  | content                                     |
+      | Star Wars | 2009-03-27 | default | These aren't the droids you're looking for. |
+    And I have a default layout that contains "By {{ '_Obi-wan_' | markdownify:'inline' }}"
+    When I run jekyll build
+    Then I should get a zero exit status
+    And the _site directory should exist
+    And I should see "By <em>Obi-wan</em>" in "_site/2009/03/27/star-wars.html"
+
   Scenario: Sort by an arbitrary variable
     Given I have a _layouts directory
     And I have the following page:

lib/jekyll/converters/markdown/inline.rb

@@ -0,0 +1,35 @@
+class Kramdown::Parser::Inline < Kramdown::Parser::Kramdown
+  def initialize(source, options)
+    super
+    @block_parsers = [:block_html].freeze
+  end
+end
+
+module Jekyll
+  module Converters
+    class Markdown
+      class Inline < Converter
+        safe true
+        priority :low
+
+        def initialize(config)
+          Jekyll::External.require_with_graceful_fail "kramdown"
+          @config = config["kramdown"].dup || {}
+          @config[:input] = :Inline
+        end
+
+        def matches(_)
+          false
+        end
+
+        def output_ext(_)
+          nil
+        end
+
+        def convert(content)
+          Kramdown::Document.new(content, @config).to_html.chomp
+        end
+      end
+    end
+  end
+end

lib/jekyll/filters.rb

@@ -13,9 +13,13 @@ module Jekyll
     # input - The Markdown String to convert.
     #
     # Returns the HTML formatted String.
-    def markdownify(input)
+    def markdownify(input, mode = nil)
       site = @context.registers[:site]
-      converter = site.find_converter_instance(Jekyll::Converters::Markdown)
+      if mode.to_s == "inline"
+        converter = site.find_converter_instance(Jekyll::Converters::Markdown::Inline)
+      else
+        converter = site.find_converter_instance(Jekyll::Converters::Markdown)
+      end
       converter.convert(input.to_s)
     end
 

test/test_filters.rb

@@ -57,6 +57,20 @@ class TestFilters < JekyllUnitTest
       )
     end
 
+    should "markdownify with simple string in inline mode" do
+      assert_equal(
+        "one <em>simple</em> string",
+        @filter.markdownify("one _simple_ string", :inline)
+      )
+    end
+
+    should "markdownify with multi-line string in inline mode" do
+      assert_equal(
+        "first line\nsecond line",
+        @filter.markdownify("first line\n\nsecond line", :inline)
+      )
+    end
+
     context "smartify filter" do
       should "convert quotes and typographic characters" do
         assert_equal(