fix message codecs for the Web (#36549)

packages/flutter/lib/src/services/message_codecs.dart

@@ -338,6 +338,14 @@ class StandardMessageCodec implements MessageCodec<dynamic> {
       buffer.putUint8(_valueNull);
     } else if (value is bool) {
       buffer.putUint8(value ? _valueTrue : _valueFalse);
+    } else if (value is double) {  // Double precedes int because in JS everything is a double.
+                                   // Therefore in JS, both `is int` and `is double` always
+                                   // return `true`. If we check int first, we'll end up treating
+                                   // all numbers as ints and attempt the int32/int64 conversion,
+                                   // which is wrong. This precedence rule is irrelevant when
+                                   // decoding because we use tags to detect the type of value.
+      buffer.putUint8(_valueFloat64);
+      buffer.putFloat64(value);
     } else if (value is int) {
       if (-0x7fffffff - 1 <= value && value <= 0x7fffffff) {
         buffer.putUint8(_valueInt32);
@@ -346,9 +354,6 @@ class StandardMessageCodec implements MessageCodec<dynamic> {
         buffer.putUint8(_valueInt64);
         buffer.putInt64(value);
       }
-    } else if (value is double) {
-      buffer.putUint8(_valueFloat64);
-      buffer.putFloat64(value);
     } else if (value is String) {
       buffer.putUint8(_valueString);
       final List<int> bytes = utf8.encoder.convert(value);

packages/flutter/test/services/message_codecs_testing.dart

+// Copyright 2019 The Chromium Authors. 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:typed_data';
+
+import 'package:flutter/services.dart';
+import '../flutter_test_alternative.dart';
+
+void checkEncoding<T>(MessageCodec<T> codec, T message, List<int> expectedBytes) {
+  final ByteData encoded = codec.encodeMessage(message);
+  expect(
+    encoded.buffer.asUint8List(0, encoded.lengthInBytes),
+    orderedEquals(expectedBytes),
+  );
+}
+
+void checkEncodeDecode<T>(MessageCodec<T> codec, T message) {
+  final ByteData encoded = codec.encodeMessage(message);
+  final T decoded = codec.decodeMessage(encoded);
+  if (message == null) {
+    expect(encoded, isNull);
+    expect(decoded, isNull);
+  } else {
+    expect(deepEquals(message, decoded), isTrue);
+    final ByteData encodedAgain = codec.encodeMessage(decoded);
+    expect(
+      encodedAgain.buffer.asUint8List(),
+      orderedEquals(encoded.buffer.asUint8List()),
+    );
+  }
+}
+
+bool deepEquals(dynamic valueA, dynamic valueB) {
+  if (valueA is TypedData)
+    return valueB is TypedData && deepEqualsTypedData(valueA, valueB);
+  if (valueA is List)
+    return valueB is List && deepEqualsList(valueA, valueB);
+  if (valueA is Map)
+    return valueB is Map && deepEqualsMap(valueA, valueB);
+  if (valueA is double && valueA.isNaN)
+    return valueB is double && valueB.isNaN;
+  return valueA == valueB;
+}
+
+bool deepEqualsTypedData(TypedData valueA, TypedData valueB) {
+  if (valueA is ByteData) {
+    return valueB is ByteData
+        && deepEqualsList(
+            valueA.buffer.asUint8List(), valueB.buffer.asUint8List());
+  }
+  if (valueA is Uint8List)
+    return valueB is Uint8List && deepEqualsList(valueA, valueB);
+  if (valueA is Int32List)
+    return valueB is Int32List && deepEqualsList(valueA, valueB);
+  if (valueA is Int64List)
+    return valueB is Int64List && deepEqualsList(valueA, valueB);
+  if (valueA is Float64List)
+    return valueB is Float64List && deepEqualsList(valueA, valueB);
+  throw 'Unexpected typed data: $valueA';
+}
+
+bool deepEqualsList(List<dynamic> valueA, List<dynamic> valueB) {
+  if (valueA.length != valueB.length)
+    return false;
+  for (int i = 0; i < valueA.length; i++) {
+    if (!deepEquals(valueA[i], valueB[i]))
+      return false;
+  }
+  return true;
+}
+
+bool deepEqualsMap(Map<dynamic, dynamic> valueA, Map<dynamic, dynamic> valueB) {
+  if (valueA.length != valueB.length)
+    return false;
+  for (final dynamic key in valueA.keys) {
+    if (!valueB.containsKey(key) || !deepEquals(valueA[key], valueB[key]))
+      return false;
+  }
+  return true;
+}

packages/flutter/test/services/message_codecs_vm_test.dart

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file contains tests that are only supported by the Dart VM. For
+// example, on the Web there's no way to express large integers.
+@TestOn('!chrome')
+
+import 'dart:typed_data';
+
+import 'package:flutter/services.dart';
+import '../flutter_test_alternative.dart';
+import 'message_codecs_testing.dart';
+
+void main() {
+  group('JSON message codec', () {
+    const MessageCodec<dynamic> json = JSONMessageCodec();
+    test('should encode and decode big numbers', () {
+      checkEncodeDecode<dynamic>(json, 9223372036854775807);
+      checkEncodeDecode<dynamic>(json, -9223372036854775807);
+    });
+    test('should encode and decode list with a big number', () {
+      final List<dynamic> message = <dynamic>[-7000000000000000007];
+      checkEncodeDecode<dynamic>(json, message);
+    });
+  });
+  group('Standard message codec', () {
+    const MessageCodec<dynamic> standard = StandardMessageCodec();
+    test('should encode integers correctly at boundary cases', () {
+      checkEncoding<dynamic>(
+        standard,
+        -0x7fffffff - 1,
+        <int>[3, 0x00, 0x00, 0x00, 0x80],
+      );
+      checkEncoding<dynamic>(
+        standard,
+        -0x7fffffff - 2,
+        <int>[4, 0xff, 0xff, 0xff, 0x7f, 0xff, 0xff, 0xff, 0xff],
+      );
+      checkEncoding<dynamic>(
+        standard,
+        0x7fffffff,
+        <int>[3, 0xff, 0xff, 0xff, 0x7f],
+      );
+      checkEncoding<dynamic>(
+        standard,
+        0x7fffffff + 1,
+        <int>[4, 0x00, 0x00, 0x00, 0x80, 0x00, 0x00, 0x00, 0x00],
+      );
+      checkEncoding<dynamic>(
+        standard,
+        -0x7fffffffffffffff - 1,
+        <int>[4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80],
+      );
+      checkEncoding<dynamic>(
+        standard,
+        -0x7fffffffffffffff - 2,
+        <int>[4, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f],
+      );
+      checkEncoding<dynamic>(
+        standard,
+        0x7fffffffffffffff,
+        <int>[4, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f],
+      );
+      checkEncoding<dynamic>(
+        standard,
+        0x7fffffffffffffff + 1,
+        <int>[4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x80],
+      );
+    });
+    test('should encode and decode big numbers', () {
+      checkEncodeDecode<dynamic>(standard, 9223372036854775807);
+      checkEncodeDecode<dynamic>(standard, -9223372036854775807);
+    });
+    test('should encode and decode a list containing big numbers', () {
+      final List<dynamic> message = <dynamic>[
+        -7000000000000000007,
+        Int64List.fromList(
+            <int>[-0x7fffffffffffffff - 1, 0, 0x7fffffffffffffff]),
+      ];
+      checkEncodeDecode<dynamic>(standard, message);
+    });
+  });
+}