[refactoring] Catch error when first argument is an instance of Error

Author: ben-lin

lib/flow.js

@@ -128,6 +128,10 @@ Flow.prototype = {
  * @param {Array} args Arguments to be passed to the current series function.
  */
   _run_series : function ( args ){
+    if( args.length && args[ 0 ] instanceof Error ){
+      return this._error( args[ 0 ]);
+    }
+
     try{
       this._series.shift().apply( this, args );
     }catch( err ){

test/flow.js

@@ -351,5 +351,40 @@ module.exports = {
         callback();
       }, 150 );
     });
+  },
+
+  'error handeling' : function ( callback ){
+    var flow = new Flow( 5, 6, 7 );
+
+    flow.series( function ( x, y, z, next ){
+      setTimeout( function (){
+        x.should.equal( 7 );
+        y.should.equal( 6 );
+        z.should.equal( 7 );
+        next( new Error( 'Error found' ));
+      }, 200 );
+    }, 7 ).
+
+    series( function ( x, y, z, next ){
+      setTimeout( function (){
+        x.should.equal( 11 );
+        y.should.equal( 10 );
+        z.should.equal( 55 );
+        next( 1000 );
+      }, 100 );
+    }, 9, 10, 55 ).
+
+    error( function ( err ){
+      console.log( 'error handeling', err );
+    }).
+
+    end( function ( x ){
+      setTimeout( function (){
+        x.should.equal( 1000 );
+
+        console.log( 'this shouldn\t be seen' );
+        callback();
+      }, 150 );
+    });
   }
 };