Bug 112436 [search] is unkind to its participants
PDE is on its way to becoming a Java-seach-participant to show hits in manifest files. It's all going swimmingly, except that annotations are not being created when the manifest editor opens. The problem seems to be in JavaSearchResult#computeContainedMatches(...). This method returns an empty array if the file being opened is not a Java file. This clearly causes a problem for PDE who is solely interested in manifest files (manifest.mf and plugin.xml). So the editor opens but no pretty yellow arrows or blue markers.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/search/JavaSearchResult.java
for (int i= 0; i < m.length; i++) {
				matches.add(m[i]);
			}
		}
		if (element instanceof IParent) {
			IParent parent= (IParent) element;
			try {
				IJavaElement[] children= parent.getChildren();
				for (int i= 0; i < children.length; i++) {
					collectMatches(matches, children[i]);
				}
			} catch (JavaModelException e) {
				
			}
		}
	}
	/* (non-Javadoc)
	 * @see org.eclipse.search.ui.ISearchResultCategory#getFile(java.lang.Object)
	 */
	public IFile getFile(Object element) {
		if (element instanceof IJavaElement) {
			IJavaElement javaElement= (IJavaElement) element;
			IFile matchFile= null;
			ICompilationUnit cu= (ICompilationUnit) javaElement.getAncestor(IJavaElement.COMPILATION_UNIT);
			if (cu != null) {
				matchFile= (IFile) cu.getResource();
			} else {
				IClassFile cf= (IClassFile) javaElement.getAncestor(IJavaElement.CLASS_FILE);
				if (cf != null)
					matchFile= (IFile) cf.getResource();