mongodb/jstests/aggregation/bugs/cond.js

// $cond returns the evaluated second argument if the first evaluates to true but the evaluated
// third argument if the first evaluates to false.
(function() {
    "use strict";
    load('jstests/aggregation/extras/utils.js');

    const coll = db.jstests_aggregation_cond;
    coll.drop();

    coll.save({});

    function assertError(expectedErrorCode, condSpec) {
        assertErrorCode(coll, {$project: {a: {$cond: condSpec}}}, expectedErrorCode);
    }

    function assertResult(expectedResult, arg) {
        assert.eq(expectedResult, coll.aggregate({$project: {a: {$cond: arg}}}).toArray()[0].a);
    }

    // Wrong number of args.
    assertError(16020, []);
    assertError(16020, [1]);
    assertError(16020, [false]);
    assertError(16020, [1, 1]);
    assertError(16020, [1, 1, null, 1]);
    assertError(16020, [1, 1, 1, undefined]);

    // Bad object cases.
    assertError(17080, {"else": 1, then: 1});
    assertError(17081, {"if": 1, "else": 1});
    assertError(17082, {"if": 1, then: 1});
    assertError(17083, {asdf: 1, then: 1});

    // Literal expressions.
    assertResult(1, [true, 1, 2]);
    assertResult(2, [false, 1, 2]);

    // Order independence for object case.
    assertResult(1, {"if": true, "then": 1, "else": 2});
    assertResult(1, {"if": true, "else": 2, "then": 1});
    assertResult(1, {"then": 1, "if": true, "else": 2});
    assertResult(1, {"then": 1, "else": 2, "if": true});
    assertResult(1, {"else": 2, "then": 1, "if": true});
    assertResult(1, {"else": 2, "if": true, "then": 1});

    // Computed expressions.
    assertResult(1, [{$and: []}, {$add: [1]}, {$add: [1, 1]}]);
    assertResult(2, [{$or: []}, {$add: [1]}, {$add: [1, 1]}]);

    assert(coll.drop());
    assert.writeOK(coll.insert({t: true, f: false, x: 'foo', y: 'bar'}));

    // Field path expressions.
    assertResult('foo', ['$t', '$x', '$y']);
    assertResult('bar', ['$f', '$x', '$y']);

    assert(coll.drop());
    assert.writeOK(coll.insert({}));

    // Coerce to bool.
    assertResult('a', [1, 'a', 'b']);
    assertResult('a', ['', 'a', 'b']);
    assertResult('b', [0, 'a', 'b']);

    // Nested.
    assert(coll.drop());
    assert.writeOK(coll.insert({noonSense: 'am', mealCombined: 'no'}));
    assert.writeOK(coll.insert({noonSense: 'am', mealCombined: 'yes'}));
    assert.writeOK(coll.insert({noonSense: 'pm', mealCombined: 'yes'}));
    assert.writeOK(coll.insert({noonSense: 'pm', mealCombined: 'no'}));
    assert.eq(
        ['breakfast', 'brunch', 'dinner', 'linner'],
        coll.aggregate([
                {
                  $project: {
                      meal: {
                          $cond: [
                              {$eq: ['$noonSense', 'am']},
                              {$cond: [{$eq: ['$mealCombined', 'yes']}, 'brunch', 'breakfast']},
                              {$cond: [{$eq: ['$mealCombined', 'yes']}, 'linner', 'dinner']}
                          ]
                      }
                  }
                },
                {$sort: {meal: 1}}
            ])
            .map(doc => doc.meal));
}());