code: function compileFile(locals, cb) {
      getSourceTemplate(function(err, source, template) {
        if (err) return cb(err);
  
        // Try to get the layout
        parseLayout(source, filename, function(err, layoutTemplates) {
          if (err) return cb(err);
  
          function renderIt(layoutTemplates) {
            if (self._options.beautify) {
              return render(template, locals, layoutTemplates, function(err, html) {
                if (err) return cb(err);
                loadBeautify();
                return cb(null, self.beautify(html, self.beautifyrc));
              });
            }
            return render(template, locals, layoutTemplates, cb);
          }
  
          // Determine which layout to use
  
          if (typeof options.layout !== 'undefined' && !options.layout) {
            // If options.layout is falsy, behave as if no layout should be used - suppress defaults
            renderIt(null);
          } else if (layoutTemplates) {
            // 1. Layout specified in template
            renderIt(layoutTemplates);
          } else if (typeof options.layout !== 'undefined' && options.layout) {
            // 2. Layout specified by options from render
            var layoutFile = self.layoutPath(filename, options.layout);
            self.cacheLayout(layoutFile, options.cache, function(err, layoutTemplates) {
              if (err) return cb(err);
              renderIt(layoutTemplates);
            });
          } else if (self.defaultLayoutTemplates) {
            // 3. Default layout specified when middleware was configured.
            renderIt(self.defaultLayoutTemplates);
          } else {
            // render without a template
            renderIt(null);
          }
        });
      });
    }
docs: Compiles a file into a template and a layoutTemplate, then renders it above.