Description Andreas Mayer 2011-08-29 11:53:55 EDT

Build Identifier: I20110613-1736

If a diff model contains an UpdateReference that has neither a left nor a right target, then the following NPE is thrown once its parent is expanded and the UpdateReferenceItemProvider is asked for an image for the UpdateReference instance. In addition, UpdateReferenceItemProvider.getText(...) also returns a wrong textual description ("Reference ... in ... changed from null to null" instead of "... changed from XYZ to null") here.

java.lang.NullPointerException
        at org.eclipse.emf.edit.provider.ComposedAdapterFactory.adapt(ComposedAdapterFactory.java:340)
        at org.eclipse.emf.edit.provider.ComposedAdapterFactory.adapt(ComposedAdapterFactory.java:277)
        at org.eclipse.emf.compare.util.AdapterUtils.adapt(AdapterUtils.java:55)
        at org.eclipse.emf.compare.util.AdapterUtils.getItemProviderImage(AdapterUtils.java:79)
        at org.eclipse.emf.compare.diff.provider.UpdateReferenceItemProvider.getImage(UpdateReferenceItemProvider.java:58)
        at org.eclipse.emf.edit.ui.provider.AdapterFactoryLabelProvider.getImage(AdapterFactoryLabelProvider.java:336)
        at org.eclipse.emf.compare.ui.viewer.structure.ModelStructureMergeViewer$ModelStructureLabelProvider.getImage(ModelStructureMergeViewer.java:432)
        at org.eclipse.jface.viewers.WrappedViewerLabelProvider.getImage(WrappedViewerLabelProvider.java:117)
        at org.eclipse.jface.viewers.WrappedViewerLabelProvider.update(WrappedViewerLabelProvider.java:165)
        at org.eclipse.jface.viewers.ViewerColumn.refresh(ViewerColumn.java:152)
        at org.eclipse.jface.viewers.AbstractTreeViewer.doUpdateItem(AbstractTreeViewer.java:938)
        at org.eclipse.jface.viewers.AbstractTreeViewer$UpdateItemSafeRunnable.run(AbstractTreeViewer.java:106)
        at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
        at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:49)
        at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:175)
	at org.eclipse.jface.viewers.AbstractTreeViewer.doUpdateItem(AbstractTreeViewer.java:1018)
        ...
   
You will get a diff model with an UpdateReference where leftTarget = rightTarget = null by comparing two models, one of which sets a reference to an object that was newly added, for example:

* Model 1

  <?xml version="1.0" encoding="UTF-8"?>
  <ecore:EPackage xmi:version="2.0"
      xmlns:xmi="http://www.omg.org/XMI"   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore"   name="mypackage">
    <eClassifiers xsi:type="ecore:EClass" name="A">
      <eStructuralFeatures xsi:type="ecore:EReference" name="b"   eType="#//B"/>
    </eClassifiers>
    <eClassifiers xsi:type="ecore:EClass" name="B"/>
  </ecore:EPackage>

* Model 2

  <?xml version="1.0" encoding="UTF-8"?>
  <ecore:EPackage xmi:version="2.0"
      xmlns:xmi="http://www.omg.org/XMI"   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore"   name="mypackage">
    <eClassifiers xsi:type="ecore:EClass" name="A">
      <eStructuralFeatures xsi:type="ecore:EReference" name="b"/>
    </eClassifiers>
  </ecore:EPackage>

This is because ReferenceCheck.createUpdateReferenceOperation(...) uses 

  EObject leftTarget = getMatchedEObject(addedValue);
  EObject rightTarget = getMatchedEObject(deletedValue);

to compute the targets. In this case addedValue has no match and deletedValue is null (or vice versa) and so both targets are null.

To fix this issue, UpdateReferenceItemProvider shouldn't use the UpdateReference's targets to compute the image and text. Instead it should use the reference value from leftElement and rightElement as already done in UpdateReferenceImpl.toString(). 

Reproducible: Always

Steps to Reproduce:
1. Compare two models, one of which sets a reference to an object that was newly added (see examples above).
2. Expand the diff element that corresponds to the change of that reference.
3. An NPE is logged and the viewer shows a wrong textual description of the change.