Outstanding issues:

• VS Code shows stale results (possibly due to cancellation of intermediate requests) during typing CompletionList.isIncomplete=true results in showing "stale" results when typing quickly due to cancelled requests microsoft/vscode#147830
• VS Code doesn't filter items client-side during typing Filter completion client-side even if the LSP returns incomplete results microsoft/vscode#168329
• Server truncates based on rank but doesn't guarantee exact matches are always included
• Server ranking tables are stale and may not rank the items you'd expect highly Bad initial completion ranking (no prefix) for named arguments #4618