jstests/aggregation/expressions/date_to_string_on_null.js


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/**
 * Tests for the $dateToString expression with the optional 'onNull' parameter.
 */
(function() {
    "use strict";

    const onNullValue = ISODate("2017-07-04T11:56:02Z");
    const coll = db.date_to_string_on_null;
    coll.drop();

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

    for (let nullishValue of[null, undefined, "$missing"]) {
        // Test that the 'onNull' value is returned when the 'date' is nullish.
        assert.eq([{_id: 0, date: onNullValue}],
                  coll.aggregate({
                          $project: {
                              date: {
                                  $dateToString: {
                                      date: nullishValue,
                                      format: "%Y-%m-%d %H:%M:%S",
                                      onNull: onNullValue
                                  }
                              }
                          }
                      })
                      .toArray());

        // Test that null is returned when the 'timezone' is nullish, regardless of the 'onNull'
        // value.
        assert.eq([{_id: 0, date: null}],
                  coll.aggregate({
                          $project: {
                              date: {
                                  $dateToString: {
                                      date: "2018-02-06T11:56:02Z",
                                      format: "%Y-%m-%d %H:%M:%S",
                                      timezone: nullishValue,
                                      onNull: onNullValue
                                  }
                              }
                          }
                      })
                      .toArray());
    }

    // Test that 'onNull' can be any type, not just an ISODate.
    for (let onNullValue of[{}, 5, "Not a date", null, undefined]) {
        assert.eq([{_id: 0, date: onNullValue}],
                  coll.aggregate({
                          $project: {
                              date: {
                                  $dateToString: {
                                      date: "$missing",
                                      format: "%Y-%m-%d %H:%M:%S",
                                      onNull: onNullValue
                                  }
                              }
                          }
                      })
                      .toArray());
    }

    // Test that 'onNull' can be missing, resulting in no output field when used within a $project
    // stage.
    assert.eq(
        [{_id: 0}],
        coll.aggregate({
                $project: {
                    date: {
                        $dateToString:
                            {date: "$missing", format: "%Y-%m-%d %H:%M:%S", onNull: "$missing"}
                    }
                }
            })
            .toArray());
})();