From 6ef81940b89cf52c9c5f9074adaa88d57f2b00d0 Mon Sep 17 00:00:00 2001
From: Christoph Grabo <asaaki@mannaz.cc>
Date: Tue, 6 Oct 2020 19:03:27 +0200
Subject: [PATCH] Add language class to code tag

class attribute is only added if a language is available.
It uses the format "language-xxx" as per commonmark spec:
https://spec.commonmark.org/0.29/#example-112 ff.
---
 components/rendering/src/markdown.rs   | 20 +++++++++++++++++++-
 components/rendering/tests/markdown.rs |  4 ++--
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/components/rendering/src/markdown.rs b/components/rendering/src/markdown.rs
index ff419fbd..b60dc0ed 100644
--- a/components/rendering/src/markdown.rs
+++ b/components/rendering/src/markdown.rs
@@ -203,7 +203,19 @@ pub fn markdown_to_html(content: &str, context: &RenderContext) -> Result<Render
                         }
                     }
                     Event::Start(Tag::CodeBlock(ref kind)) => {
+                        let mut language = None;
+                        match kind {
+                            CodeBlockKind::Fenced(fence_info) => {
+                                let fence_info = fence::FenceSettings::new(fence_info);
+                                language = fence_info.language;
+                            },
+                            _ => {}
+                        };
                         if !context.config.highlight_code {
+                            if let Some(lang) = language {
+                                let html = format!(r#"<pre><code class="language-{}">"#, lang);
+                                return Event::Html(html.into());
+                            }
                             return Event::Html("<pre><code>".into());
                         }
 
@@ -227,7 +239,13 @@ pub fn markdown_to_html(content: &str, context: &RenderContext) -> Result<Render
                         };
                         let snippet = start_highlighted_html_snippet(theme);
                         let mut html = snippet.0;
-                        html.push_str("<code>");
+                        if let Some(lang) = language {
+                            html.push_str(r#"<code class="language-"#);
+                            html.push_str(lang);
+                            html.push_str(r#"">"#);
+                        } else {
+                            html.push_str("<code>");
+                        }
                         Event::Html(html.into())
                     }
                     Event::End(Tag::CodeBlock(_)) => {
diff --git a/components/rendering/tests/markdown.rs b/components/rendering/tests/markdown.rs
index e37f9212..d1dcfdfd 100644
--- a/components/rendering/tests/markdown.rs
+++ b/components/rendering/tests/markdown.rs
@@ -53,7 +53,7 @@ fn can_highlight_code_block_with_lang() {
     let res = render_content("```python\nlist.append(1)\n```", &context).unwrap();
     assert_eq!(
         res.body,
-        "<pre style=\"background-color:#2b303b;\">\n<code><span style=\"color:#c0c5ce;\">list.</span><span style=\"color:#bf616a;\">append</span><span style=\"color:#c0c5ce;\">(</span><span style=\"color:#d08770;\">1</span><span style=\"color:#c0c5ce;\">)\n</span></code></pre>"
+        "<pre style=\"background-color:#2b303b;\">\n<code class=\"language-python\"><span style=\"color:#c0c5ce;\">list.</span><span style=\"color:#bf616a;\">append</span><span style=\"color:#c0c5ce;\">(</span><span style=\"color:#d08770;\">1</span><span style=\"color:#c0c5ce;\">)\n</span></code></pre>"
     );
 }
 
@@ -68,7 +68,7 @@ fn can_higlight_code_block_with_unknown_lang() {
     // defaults to plain text
     assert_eq!(
         res.body,
-        "<pre style=\"background-color:#2b303b;\">\n<code><span style=\"color:#c0c5ce;\">list.append(1)\n</span></code></pre>"
+        "<pre style=\"background-color:#2b303b;\">\n<code class=\"language-yolo\"><span style=\"color:#c0c5ce;\">list.append(1)\n</span></code></pre>"
     );
 }