Completion items are not sorted when extra text typed after completion invocation

The LSContentAssistProcessor sorts completions based on the rank when completions are first computed. If extra chars are typed after the initial CA invocation then the list of proposals is filtered (as invalid proposals are filtered out) but never sorted again based on the document filter text. The generic editor ContentAssistant is null thus nothing is sorted after the initial invocation. The result is irrelevant completion proposals ends up at the top of the list.
It'd be great if somehow we could set the sorter on the ContentAssistant... I couldn't find a way unfortunately and ended up using reflection just to test the hypothesis.
After writing the code below in lsp4e i was able to achieve the desired effect:

	private void installSorterIfAbsetnt(ITextViewer viewer) {
		if (viewer instanceof SourceViewer) {
			try {
				Field f = SourceViewer.class.getDeclaredField("fContentAssistant"); //$NON-NLS-1$
				f.setAccessible(true);
				Object o = f.get(viewer);
				if (o instanceof ContentAssistant) {
					ContentAssistant contentAssitant = (ContentAssistant) o;
					Field sorterField = ContentAssistant.class.getDeclaredField("fSorter"); //$NON-NLS-1$
					sorterField.setAccessible(true);
					if (sorterField.get(contentAssitant) == null) {
						contentAssitant.setSorter(new ICompletionProposalSorter() {

							@Override
							public int compare(ICompletionProposal p1, ICompletionProposal p2) {
								if (p1 instanceof LSCompletionProposal && p2 instanceof LSCompletionProposal) {
									return proposalComparator.compare((LSCompletionProposal) p1, (LSCompletionProposal) p2);
								}
								return 0;
							}
						});
					}
				}
			} catch (Exception e) {
				// ignore
			}
		}
	}

	@Override
	public ICompletionProposal[] computeCompletionProposals(ITextViewer viewer, int offset) {
		installSorterIfAbsetnt(viewer);

		IDocument document = viewer.getDocument();

                ....

I'd be more than happy to provide a patch if someone points in the right direction to implement this elegantly :-)

Start with LSContentAssistProcessor.computeCompletionProposals and trace how ContentAssistant filters proposals after extra document text is typed. Review the SourceViewer and ContentAssistant sorter behavior, then reproduce the issue with completion proposals; done means irrelevant proposals no longer remain at the top after filtering without relying on reflection.