CSHARP-2305: Support $numberInt when reading extended JSON.

Author: rstam

src/MongoDB.Bson/IO/JsonReader.cs

@@ -1218,6 +1218,7 @@ private BsonType ParseExtendedJson()
                     case "$maxkey": case "$maxKey": _currentValue = ParseMaxKeyExtendedJson(); return BsonType.MaxKey;
                     case "$minkey": case "$minKey": _currentValue = ParseMinKeyExtendedJson(); return BsonType.MinKey;
                     case "$numberDecimal": _currentValue = ParseNumberDecimalExtendedJson(); return BsonType.Decimal128;
+                    case "$numberInt": _currentValue = ParseNumberIntExtendedJson(); return BsonType.Int32;
                     case "$numberLong": _currentValue = ParseNumberLongExtendedJson(); return BsonType.Int64;
                     case "$oid": _currentValue = ParseObjectIdExtendedJson(); return BsonType.ObjectId;
                     case "$regex": _currentValue = ParseRegularExpressionExtendedJson(); return BsonType.RegularExpression;
@@ -1548,6 +1549,26 @@ private BsonValue ParseNumberDecimalExtendedJson()
             return (BsonDecimal128)value;
         }
 
+        private BsonValue ParseNumberIntExtendedJson()
+        {
+            VerifyToken(":");
+
+            int value;
+            var valueToken = PopToken();
+            if (valueToken.Type == JsonTokenType.Int32)
+            {
+                value = valueToken.Int32Value;
+            }
+            else
+            {
+                var message = string.Format("JSON reader expected an integer but found '{0}'.", valueToken.Lexeme);
+                throw new FormatException(message);
+            }
+
+            VerifyToken("}");
+            return (BsonInt32)value;
+        }
+
         private BsonValue ParseNumberLongExtendedJson()
         {
             VerifyToken(":");

tests/MongoDB.Bson.Tests/IO/JsonReaderTests.cs

@@ -525,6 +525,21 @@ public void TestInt32()
             Assert.Equal(json, BsonSerializer.Deserialize<int>(json).ToJson());
         }
 
+        [Theory]
+        [InlineData("{ $numberInt: 1 }", 1)]
+        [InlineData("{ $numberInt: -2147483648 }", -2147483648)]
+        [InlineData("{ $numberInt: 2147483647 }", 2147483647)]
+        public void TestInt32ExtendedJson(string json, int expectedResult)
+        {
+            using (var reader = new JsonReader(json))
+            {
+                var result = reader.ReadInt32();
+
+                result.Should().Be(expectedResult);
+                reader.IsAtEndOfFile().Should().BeTrue();
+            }
+        }
+
         [Theory]
         [InlineData("Number(123)")]
         [InlineData("NumberInt(123)")]