feat(modeling/BpmnLayouter): layout Element -> Element loops

Closes #824

lib/features/modeling/BpmnLayouter.js

@@ -105,10 +105,17 @@ BpmnLayouter.prototype.layoutConnection = function(connection, hints) {
   //
   // (1) outgoing of BoundaryEvents -> layout based on attach orientation and target orientation
   // (2) incoming / outgoing of Gateway -> v:h (outgoing), h:v (incoming)
+  // (3) loops from / to the same element
   //
   if (is(connection, 'bpmn:SequenceFlow') ||
       isCompensationAssociation(connection)) {
 
+    if (source === target) {
+      manhattanOptions = {
+        preferredLayouts: [ 'b:l' ]
+      };
+    } else
+
     if (is(source, 'bpmn:BoundaryEvent')) {
 
       manhattanOptions = {
@@ -136,6 +143,7 @@ BpmnLayouter.prototype.layoutConnection = function(connection, hints) {
         preferredLayouts: [ 'h:h' ]
       };
     }
+
   }
 
   if (manhattanOptions) {

lib/features/rules/BpmnRules.js

@@ -378,15 +378,6 @@ function canConnect(source, target, connection) {
     return null;
   }
 
-  // See https://github.com/bpmn-io/bpmn-js/issues/178
-  // as a workround we disallow connections with same
-  // target and source element.
-  // This rule must be removed if a auto layout for this
-  // connections is implemented.
-  if (isSame(source, target)) {
-    return false;
-  }
-
   if (!is(connection, 'bpmn:DataAssociation')) {
 
     if (canConnectMessageFlow(source, target)) {

test/spec/features/modeling/layout/LayoutSequenceFlowSpec.js

@@ -18,7 +18,6 @@ import coreModule from 'lib/core';
 
 describe('features/modeling - layout', function() {
 
-
   describe.skip('overall experience, flow elements', function() {
 
     var diagramXML = require('./LayoutSequenceFlowSpec.flowElements.bpmn');
@@ -177,6 +176,26 @@ describe('features/modeling - layout', function() {
     beforeEach(bootstrapModeler(diagramXML, { modules: testModules }));
 
 
+    describe('loops', function() {
+
+      it('should layout loop', function() {
+
+        // when
+        var connection = connect('Task_1', 'Task_1');
+
+        // then
+        expect(connection).to.have.waypoints([
+          { x: 332, y: 260 },
+          { x: 332, y: 280 },
+          { x: 262, y: 280 },
+          { x: 262, y: 220 },
+          { x: 282, y: 220 }
+        ]);
+      });
+
+    });
+
+
     describe('gateway layout', function() {
 
       it('should layout v:h after Gateway', inject(function() {

test/spec/features/rules/BpmnRulesSpec.js

@@ -328,6 +328,17 @@ describe('features/modeling/rules - BpmnRules', function() {
       });
     }));
 
+
+    it('connect Task -> Task', inject(function() {
+
+      expectCanConnect('Task', 'Task', {
+        sequenceFlow: true,
+        messageFlow: false,
+        association: false,
+        dataAssociation: false
+      });
+    }));
+
   });