Automatically enable the fenced_code_blocks option for HTML_TOC

Since some languages rely on the sharp to comment code, the output
may be unexpected as titles begin with a sharp in Markdown.

Refs #451.

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+* Automatically enable the `fenced_code_blocks` option passing a
+  `HTML_TOC` object to the `Markdown` object's constructor since
+  some languages rely on the sharp to comment code.
+
 * Allow passing `Range` objects to the `nesting_level` option to have
   a higher level of customization for table of contents:
 

ext/redcarpet/rc_markdown.c

@@ -24,6 +24,7 @@
 
 VALUE rb_mRedcarpet;
 VALUE rb_cMarkdown;
+VALUE rb_cRenderHTML_TOC;
 
 extern VALUE rb_cRenderBase;
 
@@ -101,6 +102,15 @@ static VALUE rb_redcarpet_md__new(int argc, VALUE *argv, VALUE klass)
 	if (!rb_obj_is_kind_of(rb_rndr, rb_cRenderBase))
 		rb_raise(rb_eTypeError, "Invalid Renderer instance given");
 
+	/**
+	 * Automatically enable the `fenced_code_blocks` option if
+	 * given a kind of `HTML_TOC` object since many languages
+	 * like Ruby use the sharp to comment code so these comments
+	 * would be processed as titles.
+	 */
+	if (rb_obj_is_kind_of(rb_rndr, rb_cRenderHTML_TOC))
+		extensions |= MKDEXT_FENCED_CODE;
+
 	Data_Get_Struct(rb_rndr, struct rb_redcarpet_rndr, rndr);
 
 	/* Merge the current options in the @options hash */

ext/redcarpet/rc_render.c

@@ -40,10 +40,10 @@
 }
 
 extern VALUE rb_mRedcarpet;
+extern VALUE rb_cRenderHTML_TOC;
 VALUE rb_mRender;
 VALUE rb_cRenderBase;
 VALUE rb_cRenderHTML;
-VALUE rb_cRenderHTML_TOC;
 VALUE rb_mSmartyPants;
 
 #define buf2str(t) ((t) ? rb_enc_str_new((const char*)(t)->data, (t)->size, opt->active_enc) : Qnil)

test/html_toc_render_test.rb

@@ -93,4 +93,19 @@ def test_inline_markup_escaping
     assert_match "<strong>", output
     assert_no_match %r{<strong>}, output
   end
+
+  def test_ignoring_fenced_code_blocks_comments
+    markdown = <<-Markdown.strip_heredoc
+    # Hello world !
+
+    ~~~ruby
+    # This is a comment
+    ~~~
+    Markdown
+
+    output = render(markdown)
+
+    assert output.match("Hello world")
+    refute output.match("This is a comment")
+  end
 end