Problem Description

Tab completion does not include an open parenthesis

Steps to Reproduce

• Start mongosh
• Type db.agg, followed by TAB

Expected Results

Shell completes to db.aggregate(.

Actual Results

Shell completes to db.aggregate, as mongo shell does

Additional Notes

I think this is a usability issue because it's not immediately obvious what it means when you hit Enter key and it shows you:

[Function: aggregate] AsyncFunction {
  returnType: 'AggregationCursor',
  returnsPromise: true,
  serverVersions: [ '0.0.0', '999.999.999' ],
  topologies: [ 0, 2, 1 ],
  deprecated: false,
  platforms: [ 0, 1, 2 ],
  help: [Function (anonymous)] Help
}

Including the open parenthesis is a clue that you also need a close parenthesis.

Bonus points for including the close paren for commands that don't take any arguments.