disable Nunjucks when the renderer spcify that (#2593)

* disable disableNunjucks when the renderer spcify that

* format

* source may be empty

* correct styling

lib/hexo/post.js

@@ -236,13 +236,26 @@ Post.prototype.render = function(source, data, callback) {
   var config = ctx.config;
   var cache = [];
   var tag = ctx.extend.tag;
-  var isSwig = data.engine === 'swig' || (source && pathFn.extname(source) === '.swig');
+  var ext = data.engine || (source ? pathFn.extname(source) : '');
+
+  var isSwig = ext === 'swig';
+
+  var disableNunjucks = false;
+
+  if (ext && ctx.render.renderer.get(ext)) {
+
+    // disable Nunjucks when the renderer spcify that.
+
+    disableNunjucks = disableNunjucks || !!ctx.render.renderer.get(ext).disableNunjucks;
+
+  }
 
   function escapeContent(str) {
     return '<!--' + placeholder + (cache.push(str) - 1) + '-->';
   }
 
   function tagFilter(content) {
+    if (disableNunjucks) return content;
     // Replace cache data with real contents
     content = content.replace(rPlaceholder, function() {
       return cache[arguments[1]];
@@ -273,11 +286,13 @@ Post.prototype.render = function(source, data, callback) {
     if (isSwig) return data.content;
 
     // Escape all Swig tags
-    data.content = data.content
-      .replace(rSwigFullBlock, escapeContent)
-      .replace(rSwigBlock, escapeContent)
-      .replace(rSwigComment, '')
-      .replace(rSwigVar, escapeContent);
+    if (!disableNunjucks) {
+      data.content = data.content
+        .replace(rSwigFullBlock, escapeContent)
+        .replace(rSwigBlock, escapeContent)
+        .replace(rSwigComment, '')
+        .replace(rSwigVar, escapeContent);
+    }
 
     var options = data.markdown || {};
     if (!config.highlight.enable) options.highlight = null;