Allow different casings to be specified for syntax highlighting (#6354)

app/lib/redcarpet/render/html_rouge.rb

@@ -5,6 +5,13 @@ module Redcarpet
     class HTMLRouge < HTML
       include Rouge::Plugins::Redcarpet
 
+      # Rouge requires the hint language to be lower case, by overriding this
+      # method we can allow the hint language to be specified with other casings
+      # eg. `Ada` instead of `ada`
+      def block_code(code, language)
+        super(code, language.to_s.downcase)
+      end
+
       def link(link, _title, content)
         # Probably not the best fix but it does it's job of preventing
         # a nested links.

spec/labor/markdown_parser_spec.rb

@@ -314,4 +314,21 @@ RSpec.describe MarkdownParser, type: :labor do
       expect(generate_and_parse_markdown(code_block)).to include("word_<em>italic</em>_")
     end
   end
+
+  context "when adding syntax highlighting" do
+    it "defaults to plaintext" do
+      code_block = "```\ntext\n````"
+      expect(generate_and_parse_markdown(code_block)).to include("highlight plaintext")
+    end
+
+    it "adds correct syntax highlighting to codeblocks when the hint is not lowercase" do
+      code_block = "```Ada\nwith Ada.Directories;\n````"
+      expect(generate_and_parse_markdown(code_block)).to include("highlight ada")
+    end
+
+    it "adds correct syntax highlighting to codeblocks when the hint is lowercase" do
+      code_block = "```ada\nwith Ada.Directories;\n````"
+      expect(generate_and_parse_markdown(code_block)).to include("highlight ada")
+    end
+  end
 end