feat(Viewer): improve BPMN 2.0 XML parse error message

Related to #86

lib/Viewer.js

@@ -26,6 +26,23 @@ function initListeners(diagram, listeners) {
   });
 }
 
+function checkValidationError(err) {
+
+  // check if we can help the user by indicating wrong BPMN 2.0 xml
+  // (in case he or the exporting tool did not get that right)
+
+  var pattern = /unparsable content <([^>]+)> detected([\s\S]*)$/;
+  var match = pattern.exec(err.message);
+
+  if (match) {
+    err.message =
+      'unparsable content <' + match[1] + '> detected; ' +
+      'this may indicate an invalid BPMN 2.0 diagram file' + match[2];
+  }
+
+  return err;
+}
+
 /**
  * @class
  *
@@ -87,7 +104,9 @@ Viewer.prototype.importXML = function(xml, done) {
   var self = this;
 
   BpmnModel.fromXML(xml, 'bpmn:Definitions', function(err, definitions) {
+
     if (err) {
+      err = checkValidationError(err);
       return done(err);
     }
 

test/fixtures/bpmn/error/missing-namespace.bpmn

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<definitions xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:bpmn2="http://www.omg.org/spec/BPMN/20100524/MODEL" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI" xmlns:dc="http://www.omg.org/spec/DD/20100524/DC" xmlns:di="http://www.omg.org/spec/DD/20100524/DI" id="Definitions_1" targetNamespace="http://www.example.com">
+  <collaboration name="TEST">
+    <participant id="Participant_1" name="Participant Name"/>
+  </collaboration>
+  <bpmndi:BPMNDiagram id="BPMNDiagram_1" name="Default Collaboration Diagram">
+    <bpmndi:BPMNPlane id="BPMNPlane_1" >
+      <bpmndi:BPMNShape id="BPMNShape_Participant_1" bpmnElement="Participant_1" isHorizontal="true">
+        <dc:Bounds height="370.0" width="1571.0" x="30.0" y="70.0"/>
+      </bpmndi:BPMNShape>
+    </bpmndi:BPMNPlane>
+  </bpmndi:BPMNDiagram>
+</definitions>

test/spec/browser/ViewerSpec.js

@@ -75,6 +75,23 @@ describe('viewer', function() {
       });
     });
 
+
+    it('should handle missing namespace', function(done) {
+
+      var xml = fs.readFileSync('test/fixtures/bpmn/error/missing-namespace.bpmn', 'utf8');
+
+      createViewer(xml, function(err) {
+        expect(err).toBeDefined();
+        expect(err.message).toEqual(
+          'unparsable content <collaboration> detected; this may indicate an invalid BPMN 2.0 diagram file\n' +
+          '\tline: 2\n' +
+          '\tcolumn: 29\n' +
+          '\tnested error: unrecognized element <collaboration>');
+
+        done();
+      });
+    });
+
   });