Bug 31214 [Show in] Fails for Package Explorer in non-Java project
- create a simple project P - create a simple file called "x.java" in P - open it with the Default Text Editor - in the editor activate "Show in" and select Package Explorer as target -> nothing happens even if P and "x.java" are visible in the Package Explorer
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerPart.java
if (key == IShowInTargetList.class) {
			return new IShowInTargetList() {
				public String[] getShowInTargetIds() {
					return new String[] { IPageLayout.ID_RES_NAV };
				}
			};
		}
		return super.getAdapter(key);
	}
	/**
	 * Returns the tool tip text for the given element.
	 */
	String getToolTipText(Object element) {
		String result;
		if (!(element instanceof IResource)) {
			result= JavaElementLabels.getTextLabel(element, AppearanceAwareLabelProvider.DEFAULT_TEXTFLAGS);		
		} else {
			IPath path= ((IResource) element).getFullPath();
			if (path.isRoot()) {
				result= PackagesMessages.getString("PackageExplorer.title"); 
			} else {
				result= path.makeRelative().toString();
			}
		}
		
		if (fWorkingSetName == null)
			return result;
		String wsstr= PackagesMessages.getFormattedString("PackageExplorer.toolTip", new String[] { fWorkingSetName }); 
		if (result.length() == 0)
			return wsstr;