feat: add Int32 serializer

built_value/lib/serializer.dart

@@ -7,6 +7,7 @@ import 'package:built_collection/src/internal/hash.dart';
 import 'package:built_value/src/big_int_serializer.dart';
 import 'package:built_value/src/date_time_serializer.dart';
 import 'package:built_value/src/duration_serializer.dart';
+import 'package:built_value/src/int32_serializer.dart';
 import 'package:built_value/src/int64_serializer.dart';
 import 'package:built_value/src/json_object_serializer.dart';
 import 'package:built_value/src/num_serializer.dart';
@@ -67,6 +68,7 @@ abstract class Serializers {
           ..add(DoubleSerializer())
           ..add(DurationSerializer())
           ..add(IntSerializer())
+          ..add(Int32Serializer())
           ..add(Int64Serializer())
           ..add(JsonObjectSerializer())
           ..add(NullSerializer())

built_value/lib/src/int32_serializer.dart

@@ -0,0 +1,27 @@
+// Copyright (c) 2023, Google Inc. Please see the AUTHORS file for details.
+// All rights reserved. Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+import 'package:built_collection/built_collection.dart';
+import 'package:built_value/serializer.dart';
+import 'package:fixnum/fixnum.dart';
+
+class Int32Serializer implements PrimitiveSerializer<Int32> {
+  final bool structured = false;
+  @override
+  final Iterable<Type> types = BuiltList<Type>([Int32]);
+  @override
+  final String wireName = 'Int32';
+
+  @override
+  Object serialize(Serializers serializers, Int32 int32,
+      {FullType specifiedType = FullType.unspecified}) {
+    return int32.toInt();
+  }
+
+  @override
+  Int32 deserialize(Serializers serializers, Object? serialized,
+      {FullType specifiedType = FullType.unspecified}) {
+    return Int32(serialized as int);
+  }
+}

built_value/test/int32_serializer_test.dart

@@ -0,0 +1,46 @@
+// Copyright (c) 2023, Google Inc. Please see the AUTHORS file for details.
+// All rights reserved. Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+import 'dart:convert';
+
+import 'package:built_value/serializer.dart';
+import 'package:fixnum/fixnum.dart';
+import 'package:test/test.dart';
+
+void main() {
+  var serializers = Serializers();
+
+  group('int32 with known specifiedType', () {
+    var data = Int32.MAX_VALUE;
+    var serialized = Int32.MAX_VALUE.toInt();
+    var specifiedType = const FullType(Int32);
+
+    test('can be serialized', () {
+      expect(serializers.serialize(data, specifiedType: specifiedType),
+          serialized);
+    });
+
+    test('can be deserialized', () {
+      expect(serializers.deserialize(serialized, specifiedType: specifiedType),
+          data);
+    });
+  });
+
+  group('int32 with unknown specifiedType', () {
+    var data = Int32.MIN_VALUE;
+    var serialized =
+        json.decode(json.encode(['Int32', Int32.MIN_VALUE.toInt()])) as Object;
+    var specifiedType = FullType.unspecified;
+
+    test('can be serialized', () {
+      expect(serializers.serialize(data, specifiedType: specifiedType),
+          serialized);
+    });
+
+    test('can be deserialized', () {
+      expect(serializers.deserialize(serialized, specifiedType: specifiedType),
+          data);
+    });
+  });
+}