Bug 31556 Export jar from Navigator view fails
(M5 build) In Navigator view (resource perspective), right-click on a src/ directory containing your sources, select export->jar file and the package selector opens with no resource selected (and finish button disabled); but it seems that the src/ dir is really selected, because if you re-select it in the window, it ends up with a "jar creation failed" and a lot of duplicate entries in the error log. If you try the same from the Projects view (Java browsing perspective), it works fine.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarPackageWizardPage.java
if (result.isOK() && workspace.getRoot().exists(path))
			return workspace.getRoot().findMember(path);
		return null;
	}
	/**
	 * Creates the checkbox tree and list for selecting resources.
	 *
	 * @param parent the parent control
	 */
	protected void createInputGroup(Composite parent) {
		int labelFlags= JavaElementLabelProvider.SHOW_BASICS
						| JavaElementLabelProvider.SHOW_OVERLAY_ICONS
						| JavaElementLabelProvider.SHOW_SMALL_ICONS;
		ITreeContentProvider treeContentProvider=
			new StandardJavaElementContentProvider() {
				public boolean hasChildren(Object element) {
					
					return !(element instanceof IPackageFragment) && super.hasChildren(element);
				}
			};
		fInputGroup= new CheckboxTreeAndListGroup(
					parent,
					JavaCore.create(ResourcesPlugin.getWorkspace().getRoot()),
					treeContentProvider,
					new JavaElementLabelProvider(labelFlags),
					new StandardJavaElementContentProvider(),
					new JavaElementLabelProvider(labelFlags),
					SWT.NONE,
					SIZING_SELECTION_WIDGET_WIDTH,
					SIZING_SELECTION_WIDGET_HEIGHT);