feat(modeling): combining two sequence flows when removing an element

combines only if removed element has one outgoing and one incoming sequence flow

Closes #433

lib/features/modeling/behavior/RemoveElementBehavior.js

@@ -0,0 +1,40 @@
+'use strict';
+
+var inherits = require('inherits');
+
+var CommandInterceptor = require('diagram-js/lib/command/CommandInterceptor');
+
+function RemoveElementBehavior(eventBus, bpmnRules, modeling) {
+
+  CommandInterceptor.call(this, eventBus);
+
+  /**
+   * Combine sequence flows when deleting an element
+   * if there is one incoming and one outgoing
+   * sequence flow
+   */
+
+  this.preExecute('shape.delete', function(e) {
+
+    var shape = e.context.shape;
+
+    if (shape.incoming.length == 1 && shape.outgoing.length == 1) {
+
+      var inConnection = shape.incoming[0],
+          outConnection = shape.outgoing[0];
+
+      var docking = outConnection.waypoints[outConnection.waypoints.length - 1];
+
+      if (bpmnRules.canConnect(inConnection.source, outConnection.target, inConnection)) {
+        modeling.reconnectEnd(inConnection, outConnection.target, docking);
+      }
+
+    }
+  });
+}
+
+inherits(RemoveElementBehavior, CommandInterceptor);
+
+RemoveElementBehavior.$inject = [ 'eventBus', 'bpmnRules', 'modeling' ];
+
+module.exports = RemoveElementBehavior;