fix(query): handle $round in $expr as array

Fix #13881

Author: vkarpov15

lib/helpers/query/cast$expr.js

@@ -29,7 +29,6 @@ const arithmeticOperatorNumber = new Set([
   '$floor',
   '$ln',
   '$log10',
-  '$round',
   '$sqrt',
   '$sin',
   '$cos',
@@ -118,6 +117,16 @@ function _castExpression(val, schema, strictQuery) {
   if (val.$size) {
     val.$size = castNumberOperator(val.$size, schema, strictQuery);
   }
+  if (val.$round) {
+    const $round = val.$round;
+    if (!Array.isArray($round) || $round.length !== 2) {
+      throw new CastError('Array', $round, '$round');
+    }
+    val.$round = [
+      castNumberOperator($round[0], schema, strictQuery),
+      castNumberOperator($round[1], schema, strictQuery)
+    ];
+  }
 
   _omitUndefined(val);
 

test/helpers/query.cast$expr.test.js

@@ -108,4 +108,11 @@ describe('castexpr', function() {
     const res = cast$expr({ $not: { $in: ['42', '$nums'] } }, testSchema);
     assert.deepStrictEqual(res, { $not: { $in: [42, '$nums'] } });
   });
+
+  it('casts $round (gh-13881)', function() {
+    const testSchema = new Schema({ value: Number });
+
+    const res = cast$expr({ $eq: [{ $round: ['$value', '00'] }, 2] }, testSchema);
+    assert.deepStrictEqual(res, { $eq: [{ $round: ['$value', 0] }, 2] });
+  });
 });