/**
 * Tests for the $dateFromString expression with the optional 'onNull' parameter.
 */
const onNullValue = ISODate("2017-07-04T11:56:02Z");
const coll = db.date_from_string_on_null;
coll.drop();

assert.commandWorked(coll.insert({_id: 0}));

// Test that the 'onNull' value is returned when the 'dateString' is nullish.
for (let inputDate of [null, undefined, "$missing"]) {
    assert.eq(
        [{_id: 0, date: onNullValue}],
        coll.aggregate({$project: {date: {$dateFromString: {dateString: inputDate, onNull: onNullValue}}}}).toArray(),
    );
}

// Test that null is returned when the 'timezone' or 'format' is nullish, regardless of the
// 'onNull' value.
for (let nullishValue of [null, undefined, "$missing"]) {
    assert.eq(
        [{_id: 0, date: null}],
        coll
            .aggregate({
                $project: {
                    date: {
                        $dateFromString: {
                            dateString: "2018-02-06T11:56:02Z",
                            format: nullishValue,
                            onNull: onNullValue,
                        },
                    },
                },
            })
            .toArray(),
    );
    assert.eq(
        [{_id: 0, date: null}],
        coll
            .aggregate({
                $project: {
                    date: {
                        $dateFromString: {
                            dateString: "2018-02-06T11:56:02Z",
                            timezone: nullishValue,
                            onNull: onNullValue,
                        },
                    },
                },
            })
            .toArray(),
    );
}

// Test that 'onNull' can be any type, not just an ISODate.
for (let onNull of [{}, 5, "Not a date", null, undefined]) {
    assert.eq(
        [{_id: 0, date: onNull}],
        coll.aggregate({$project: {date: {$dateFromString: {dateString: "$missing", onNull: onNull}}}}).toArray(),
    );
}
assert.eq(
    [{_id: 0}],
    coll.aggregate({$project: {date: {$dateFromString: {dateString: "$missing", onNull: "$missing"}}}}).toArray(),
);