Fix links without http(s) (#4155) [ci skip]

app/lib/redcarpet/render/html_rouge.rb

@@ -14,7 +14,11 @@ module Redcarpet
         @options[:link_attributes]&.each do |attribute, value|
           link_attributes += %( #{attribute}="#{value}")
         end
-        %(<a href="#{link}"#{link_attributes}>#{content}</a>)
+        if (/\A(https?:\/\/)/.match? link) || link.nil?
+          %(<a href="#{link}"#{link_attributes}>#{content}</a>)
+        else
+          %(<a href="//#{link}"#{link_attributes}>#{content}</a>)
+        end
       end
 
       def header(title, header_number)

spec/labor/markdown_parser_spec.rb

@@ -64,6 +64,21 @@ RSpec.describe MarkdownParser do
     expect(generate_and_parse_markdown(code_span)).to include random_word
   end
 
+  context "when rendering links markdown" do
+    # the following specs are testing HTMLRouge
+    it "renders properly if protocol is included" do
+      code_span = "[github](http://github.com)"
+      test = generate_and_parse_markdown(code_span)
+      expect(test).to eq("<p><a href=\"http://github.com\">github</a></p>\n\n")
+    end
+
+    it "renders properly if protocol is not included" do
+      code_span = "[github](github.com)"
+      test = generate_and_parse_markdown(code_span)
+      expect(test).to eq("<p><a href=\"//github.com\">github</a></p>\n\n")
+    end
+  end
+
   describe "mentions" do
     let(:user) { build_stubbed(:user) }
 
@@ -248,17 +263,17 @@ RSpec.describe MarkdownParser do
     end
   end
 
-  context 'when word as snake case' do
+  context "when word as snake case" do
     it "doesn't change word" do
       code_block = "word_italic_"
       expect(generate_and_parse_markdown(code_block)).to include("word_italic_")
     end
+  end
 
-    context 'when double underline' do
-      it 'renders italic' do
-        code_block = "word__italic__"
-        expect(generate_and_parse_markdown(code_block)).to include("word_<em>italic</em>_")
-      end
+  context "when double underline" do
+    it "renders italic" do
+      code_block = "word__italic__"
+      expect(generate_and_parse_markdown(code_block)).to include("word_<em>italic</em>_")
     end
   end
 end