Renderer: token stream should stay immutable, close #260

lib/renderer.js

@@ -32,11 +32,10 @@ default_rules.fence = function (tokens, idx, options, env, slf) {
   var token = tokens[idx],
       info = token.info ? unescapeAll(token.info).trim() : '',
       langName = '',
-      highlighted;
+      highlighted, i, tmpAttrs, tmpToken;
 
   if (info) {
     langName = info.split(/\s+/g)[0];
-    token.attrJoin('class', options.langPrefix + langName);
   }
 
   if (options.highlight) {
@@ -49,6 +48,30 @@ default_rules.fence = function (tokens, idx, options, env, slf) {
     return highlighted + '\n';
   }
 
+  // If language exists, inject class gently, without mudofying original token.
+  // May be, one day we will add .clone() for token and simplify this part, but
+  // now we prefer to keep things local.
+  if (info) {
+    i        = token.attrIndex('class');
+    tmpAttrs = token.attrs ? token.attrs.slice() : [];
+
+    if (i < 0) {
+      tmpAttrs.push([ 'class', options.langPrefix + langName ]);
+    } else {
+      tmpAttrs[i] += ' ' + options.langPrefix + langName;
+    }
+
+    // Fake token just to render attributes
+    tmpToken = {
+      attrs: tmpAttrs
+    };
+
+    return  '<pre><code' + slf.renderAttrs(tmpToken) + '>'
+          + highlighted
+          + '</code></pre>\n';
+  }
+
+
   return  '<pre><code' + slf.renderAttrs(token) + '>'
         + highlighted
         + '</code></pre>\n';