$filter "truthy" condition returns incorrect results about mingo HOT 4 CLOSED

Please note that mongo filters out null and false but does NOT filter out empty string

from mingo.

Thanks for reporting this bug. Need to improve testing across a number of operators given the examples aren't always sufficient.

Feel free to send a PR.

from mingo.

It appears $cond is inconsistent with mongo on empty string. I prefer mingo's implementation but for consistency.

{
	"$project": {
		"emptyString": { $cond: ['', true, false] },
		"null": { $cond: [null, true, false] },
		"undefined": { $cond: [undefined, true, false] },
		"-1": { $cond: [-1, true, false] },
		"0": { $cond: [0, true, false] },
		"1": { $cond: [1, true, false] }
	}
}

Mingo

{
  '0': false,
  '1': true,
  string: true,
  emptyString: false,
  null: false,
  undefined: false,
  '-1': true
}

Mongo

{
  '0': false,
  '1': true,
  string: true,
  emptyString: true,
  null: false,
  undefined: false,
  '-1': true
}

from mingo.

It appears $cond is inconsistent with mongo on empty string. I prefer mingo's implementation but for consistency.

{
	"$project": {
		"emptyString": { $cond: ['', true, false] },
		"null": { $cond: [null, true, false] },
		"undefined": { $cond: [undefined, true, false] },
		"-1": { $cond: [-1, true, false] },
		"0": { $cond: [0, true, false] },
		"1": { $cond: [1, true, false] }
	}
}

Mingo

{
  '0': false,
  '1': true,
  string: true,
  emptyString: false,
  null: false,
  undefined: false,
  '-1': true
}

Mongo

{
  '0': false,
  '1': true,
  string: true,
  emptyString: true,
  null: false,
  undefined: false,
  '-1': true
}

Will address all remaining cases in #321.

from mingo.