Fix #308 by escaping CSS class names

src/html.rs

@@ -159,7 +159,8 @@ pub fn css_for_theme_with_class_style(theme: &Theme, style: ClassStyle) -> Resul
             css.push_str(".code {\n");
         }
         ClassStyle::SpacedPrefixed { prefix } => {
-            css.push_str(&format!(".{}code {{\n", prefix));
+            let class = escape_css_identifier(&format!("{}code", prefix));
+            css.push_str(&format!(".{} {{\n", class));
         }
     };
     if let Some(fgc) = theme.settings.foreground {
@@ -264,16 +265,35 @@ fn scope_to_selector(s: &mut String, scope: Scope, style: ClassStyle) {
         let atom = scope.atom_at(i as usize);
         let atom_s = repo.atom_str(atom);
         s.push('.');
+        let mut class = String::new();
         match style {
             ClassStyle::Spaced => {}
             ClassStyle::SpacedPrefixed { prefix } => {
-                s.push_str(prefix);
+                class.push_str(prefix);
             }
         }
-        s.push_str(atom_s);
+        class.push_str(atom_s);
+        s.push_str(&escape_css_identifier(&class));
     }
 }
 
+/// Escape special characters in a CSS identifier.
+///
+/// See <https://www.w3.org/International/questions/qa-escapes#css_identifiers>.
+fn escape_css_identifier(identifier: &str) -> String {
+    identifier.char_indices().fold(
+        String::with_capacity(identifier.len()),
+        |mut output, (i, c)| {
+            if c.is_ascii_alphabetic() || c == '-' || c == '_' || (i > 0 && c.is_ascii_digit()) {
+                output.push(c);
+            } else {
+                output.push_str(&format!("\\{:x} ", c as u32));
+            }
+            output
+        },
+    )
+}
+
 /// Convenience method that combines `start_highlighted_html_snippet`, `styled_line_to_highlighted_html`
 /// and `HighlightLines` from `syntect::easy` to create a full highlighted HTML snippet for
 /// a string (which can contain many lines).
@@ -714,4 +734,21 @@ fn main() {
         let html = html_generator.finalize();
         assert_eq!(html, "<span class=\"source rust\"><span class=\"comment line double-slash rust\"><span class=\"punctuation definition comment rust\">//</span> Rust source\n</span><span class=\"meta function rust\"><span class=\"meta function rust\"><span class=\"storage type function rust\">fn</span> </span><span class=\"entity name function rust\">main</span></span><span class=\"meta function rust\"><span class=\"meta function parameters rust\"><span class=\"punctuation section parameters begin rust\">(</span></span><span class=\"meta function rust\"><span class=\"meta function parameters rust\"><span class=\"punctuation section parameters end rust\">)</span></span></span></span><span class=\"meta function rust\"> </span><span class=\"meta function rust\"><span class=\"meta block rust\"><span class=\"punctuation section block begin rust\">{</span>\n    <span class=\"support macro rust\">println!</span><span class=\"meta group rust\"><span class=\"punctuation section group begin rust\">(</span></span><span class=\"meta group rust\"><span class=\"string quoted double rust\"><span class=\"punctuation definition string begin rust\">&quot;</span>Hello World!<span class=\"punctuation definition string end rust\">&quot;</span></span></span><span class=\"meta group rust\"><span class=\"punctuation section group end rust\">)</span></span><span class=\"punctuation terminator rust\">;</span>\n</span><span class=\"meta block rust\"><span class=\"punctuation section block end rust\">}</span></span></span>\n</span>");
     }
+
+    #[test]
+    fn test_escape_css_identifier() {
+        assert_eq!(&escape_css_identifier("abc"), "abc");
+        assert_eq!(&escape_css_identifier("123"), "\\31 23");
+        assert_eq!(&escape_css_identifier("c++"), "c\\2b \\2b ");
+    }
+
+    /// See issue [syntect#308](<https://github.com/trishume/syntect/issues/308>).
+    #[test]
+    fn test_css_for_theme_with_class_style_issue_308() {
+        let theme_set = ThemeSet::load_defaults();
+        let theme = theme_set.themes.get("Solarized (dark)").unwrap();
+        let css = css_for_theme_with_class_style(theme, ClassStyle::Spaced).unwrap();
+        assert!(!css.contains(".c++"));
+        assert!(css.contains(".c\\2b \\2b "));
+    }
 }