Create a GFM (Github Flavored Markdown) parser

As a first step, it supports "fenced code blocks" delimited by three or more
backticks.

doc/parser/gfm.page

@@ -0,0 +1,12 @@
+---
+title: GFM Parser
+---
+# GFM Parser
+
+## Introduction
+
+Parse ["Github Flavored Markdown"](https://help.github.com/articles/github-flavored-markdown). This is a format of Markdown that is used on Github.com for most places where textual input is required, such as issues and comments. Some of the extensions, notably the "backtick fenced code blocks" are also used on other sites, for example StackOverflow.
+
+## Conformance
+
+At the moment this parser is identical to the Kramdown parser, except that it adds support for fenced code blocks using three or more backticks to delimit the block.

lib/kramdown/parser.rb

@@ -20,6 +20,7 @@ module Parser
     autoload :Kramdown, 'kramdown/parser/kramdown'
     autoload :Html, 'kramdown/parser/html'
     autoload :Markdown, 'kramdown/parser/markdown'
+    autoload :GFM, 'kramdown/parser/gfm'
 
   end
 

lib/kramdown/parser/gfm.rb

@@ -0,0 +1,31 @@
+module Kramdown
+  module Parser
+    class GFM < Kramdown::Parser::Kramdown
+
+      def initialize(source, options)
+        super
+        @block_parsers.unshift(:gfm_codeblock_fenced)
+      end
+
+      GFM_FENCED_CODEBLOCK_START = /^`{3,}/
+      #GFM_FENCED_CODEBLOCK_MATCH = /^(`{3,})\s*?(\w+)?\s*?\n(.*?)^\1`*\s*?\n/m
+      GFM_FENCED_CODEBLOCK_MATCH = /^`{3,} *(\w+)?\s*?\n(.*?)^`{3,}\s*?\n/m
+
+      # Parse the fenced codeblock at the current location.
+      def parse_gfm_codeblock_fenced
+        if @src.check(GFM_FENCED_CODEBLOCK_MATCH)
+          @src.pos += @src.matched_size
+          el = new_block_el(:codeblock, @src[2])
+          lang = @src[1].to_s.strip
+          el.attr['class'] = "language-#{lang}" unless lang.empty?
+          @tree.children << el
+          true
+        else
+          false
+        end
+      end
+      define_parser(:gfm_codeblock_fenced, GFM_FENCED_CODEBLOCK_START)
+
+    end
+  end
+end

test/test_files.rb

@@ -17,6 +17,7 @@
 class TestFiles < Test::Unit::TestCase
 
   EXCLUDE_KD_FILES = [('test/testcases/block/04_header/with_auto_ids.text' if RUBY_VERSION <= '1.8.6'), # bc of dep stringex not working
+                       'test/testcases/block/06_codeblock/backticks-syntax.text'
                      ].compact
 
   # Generate test methods for kramdown-to-xxx conversion
@@ -48,6 +49,7 @@ class TestFiles < Test::Unit::TestCase
                           'test/testcases/span/03_codespan/highlighting.html', # bc of span elements inside code element
                           'test/testcases/block/04_header/with_auto_ids.html', # bc of auto_ids=true option
                           'test/testcases/block/04_header/header_type_offset.html', # bc of header_offset option
+                          'test/testcases/block/06_codeblock/backticks-syntax.html', # only in GFM
                          ]
     Dir[File.dirname(__FILE__) + '/testcases/**/*.{html,html.19,htmlinput,htmlinput.19}'].each do |html_file|
       next if EXCLUDE_HTML_FILES.any? {|f| html_file =~ /#{f}(\.19)?$/}
@@ -85,6 +87,7 @@ def tidy_output(out)
     EXCLUDE_LATEX_FILES = ['test/testcases/span/01_link/image_in_a.text', # bc of image link
                            'test/testcases/span/01_link/imagelinks.text', # bc of image links
                            'test/testcases/span/04_footnote/markers.text', # bc of footnote in header
+                           'test/testcases/block/06_codeblock/backticks-syntax.text' # only in GFM
                           ]
     Dir[File.dirname(__FILE__) + '/testcases/**/*.text'].each do |text_file|
       next if EXCLUDE_LATEX_FILES.any? {|f| text_file =~ /#{f}$/}
@@ -121,6 +124,7 @@ def tidy_output(out)
                           'test/testcases/span/extension/comment.text',      # bc of comment text modifications (can this be avoided?)
                           'test/testcases/block/04_header/header_type_offset.text', # bc of header_offset being applied twice
                           ('test/testcases/block/04_header/with_auto_ids.text' if RUBY_VERSION <= '1.8.6'), # bc of dep stringex not working
+                          'test/testcases/block/06_codeblock/backticks-syntax.text' # only in GFM
                          ].compact
     Dir[File.dirname(__FILE__) + '/testcases/**/*.text'].each do |text_file|
       next if EXCLUDE_TEXT_FILES.any? {|f| text_file =~ /#{f}$/}
@@ -155,6 +159,7 @@ def tidy_output(out)
                              'test/testcases/block/04_header/header_type_offset.html', # bc of header_offset option
                              'test/testcases/block/16_toc/toc_exclude.html',      # bc of different attribute ordering
                              'test/testcases/span/autolinks/url_links.html',      # bc of quot entity being converted to char
+                             'test/testcases/block/06_codeblock/backticks-syntax.html' # only in GFM
                             ]
     Dir[File.dirname(__FILE__) + '/testcases/**/*.{html,html.19}'].each do |html_file|
       next if EXCLUDE_HTML_KD_FILES.any? {|f| html_file =~ /#{f}(\.19)?$/}
@@ -171,6 +176,30 @@ def tidy_output(out)
     end
   end
 
+  EXCLUDE_GFM_FILES = []
+
+  # Generate test methods for kramdown-to-gfm conversion
+  Dir[File.dirname(__FILE__) + '/testcases/**/*.text'].each do |text_file|
+    next if EXCLUDE_GFM_FILES.any? {|f| text_file =~ /#{f}$/}
+    html_file = text_file.sub(/\.text$/, '.html')
+    html_file += '.19' if RUBY_VERSION >= '1.9' && File.exist?(html_file + '.19')
+    basename = text_file.sub(/\.text$/, '')
+    next if (RUBY_VERSION >= '1.9' && File.exist?(html_file + '.19')) ||
+      (RUBY_VERSION < '1.9' && html_file =~ /\.19$/)
+    define_method('test_gfm_' + text_file.tr('.', '_') + "_to_html") do
+      opts_file = html_file.sub(/\.html(\.19)?$/, '.options')
+      opts_file = File.join(File.dirname(html_file), 'options') if !File.exist?(opts_file)
+      options = File.exist?(opts_file) ? YAML::load(File.read(opts_file)) : {:auto_ids => false, :footnote_nr => 1}
+      doc = Kramdown::Document.new(File.read(text_file), options.merge(:input => 'GFM'))
+      if File.read(html_file) != doc.to_html
+        i = rand(1000)
+        File.write("/tmp/#{i}_expected.html", File.read(html_file))
+        File.write("/tmp/#{i}_actual.html", doc.to_html)
+        puts "diff /tmp/#{i}_expected.html /tmp/#{i}_actual.html"
+      end
+      assert_equal(File.read(html_file), doc.to_html)
+    end
+  end
 
 
   # Generate test methods for asserting that converters don't modify the document tree.

test/testcases/block/06_codeblock/backticks-syntax.html

@@ -0,0 +1,23 @@
+<pre><code>Three backticks
+</code></pre>
+
+<pre><code>Four backticks
+</code></pre>
+
+<pre><code>Unbalanced bottom heavy
+</code></pre>
+
+<pre><code>Unbalanced top heavy
+</code></pre>
+
+<div><div class="CodeRay">
+  <div class="code"><pre><span class="line-numbers"><a href="#n1" name="n1">1</a></span>language no space
+</pre></div>
+</div>
+</div>
+
+<div><div class="CodeRay">
+  <div class="code"><pre><span class="line-numbers"><a href="#n1" name="n1">1</a></span>language with space
+</pre></div>
+</div>
+</div>

test/testcases/block/06_codeblock/backticks-syntax.text

@@ -0,0 +1,23 @@
+```
+Three backticks
+```
+
+````
+Four backticks
+````
+
+```
+Unbalanced bottom heavy
+``````
+
+``````
+Unbalanced top heavy
+````
+
+````ruby
+language no space
+````
+
+```` ruby
+language with space
+````