chore(importer): attempt optimization

lib/import/Importer.js

@@ -17,38 +17,42 @@ function importBpmnDiagram(diagram, definitions, done) {
   var importer = diagram.get('bpmnImporter'),
       eventBus = diagram.get('eventBus');
 
-  var warnings = [];
+  var error,
+      warnings = [];
 
-  var visitor = {
+  function parse(definitions) {
 
-    root: function(element) {
-      return importer.add(element);
-    },
+    var visitor = {
 
-    element: function(element, parentShape) {
-      return importer.add(element, parentShape);
-    },
+      root: function(element) {
+        return importer.add(element);
+      },
 
-    error: function(message, context) {
-      warnings.push({ message: message, context: context });
-    }
-  };
+      element: function(element, parentShape) {
+        return importer.add(element, parentShape);
+      },
 
-  var walker = new BpmnTreeWalker(visitor);
+      error: function(message, context) {
+        warnings.push({ message: message, context: context });
+      }
+    };
 
-  try {
-    eventBus.fire('import.start');
+    var walker = new BpmnTreeWalker(visitor);
 
     // import
     walker.handleDefinitions(definitions);
-
-    eventBus.fire('import.success', { warnings: warnings });
-
-    done(null, warnings);
-  } catch (e) {
-    eventBus.fire('import.error', { error: e });
-    done(e);
   }
+
+  eventBus.fire('import.start');
+
+  try {
+    parse(definitions);
+  } catch (e) {
+    error = e;
+  }
+
+  eventBus.fire(error ? 'import.error' : 'import.success', { error: error, warnings: warnings });
+  done(error, warnings);
 }
 
 module.exports.importBpmnDiagram = importBpmnDiagram;