fix(package_info_plus): prefer compile-time build name and number on web

packages/package_info_plus/package_info_plus/example/integration_test/package_info_plus_web_test.dart

@@ -48,7 +48,7 @@ void main() {
   group('Package Info Web', () {
     setUp(() {
       client = MockClient();
-      plugin = PackageInfoPlusWebPlugin(client);
+      plugin = PackageInfoPlusWebPlugin(client, null, null, null);
     });
 
     testWidgets('Get correct values when response status is 200', (
@@ -67,6 +67,37 @@ void main() {
       expect(versionMap.buildSignature, VERSION_JSON['build_signature']);
     });
 
+    testWidgets('Prefer the compile-time version over version.json', (
+      tester,
+    ) async {
+      when(client.get(any)).thenAnswer(
+        (_) => Future.value(http.Response(jsonEncode(VERSION_2_JSON), 200)),
+      );
+      plugin = PackageInfoPlusWebPlugin(client, null, '1.0', '1');
+
+      final versionMap = await plugin.getAll();
+
+      expect(versionMap.appName, VERSION_2_JSON['app_name']);
+      expect(versionMap.packageName, VERSION_2_JSON['package_name']);
+      expect(versionMap.version, '1.0');
+      expect(versionMap.buildNumber, '1');
+    });
+
+    testWidgets('Keep the compile-time version when version.json fails', (
+      tester,
+    ) async {
+      when(
+        client.get(any),
+      ).thenAnswer((_) => Future.value(http.Response('', 404)));
+      plugin = PackageInfoPlusWebPlugin(client, null, '1.0', '1');
+
+      final versionMap = await plugin.getAll();
+
+      expect(versionMap.appName, isEmpty);
+      expect(versionMap.version, '1.0');
+      expect(versionMap.buildNumber, '1');
+    });
+
     testWidgets('Get empty values when response status is not 200', (
       tester,
     ) async {
@@ -240,7 +271,7 @@ void main() {
     setUp(() {
       client = MockClient();
       assetManagerMock = MockAssetManager();
-      plugin = PackageInfoPlusWebPlugin(client, assetManagerMock);
+      plugin = PackageInfoPlusWebPlugin(client, assetManagerMock, null, null);
     });
 
     testWidgets('Get correct values when using the AssetManager baseUrl', (

packages/package_info_plus/package_info_plus/lib/src/package_info_plus_web.dart

@@ -8,16 +8,39 @@ import 'package:package_info_plus_platform_interface/package_info_data.dart';
 import 'package:package_info_plus_platform_interface/package_info_platform_interface.dart';
 import 'package:web/web.dart' as web;
 
+/// The build name compiled into the running bundle.
+///
+/// Injected by `flutter_tools` since Flutter 3.47 from the pubspec `version`
+/// (or `--build-name`), and exposed by Flutter as `appBuildName`. Read through
+/// the environment so older Flutter versions keep compiling.
+const String? _compileTimeBuildName = bool.hasEnvironment('FLUTTER_BUILD_NAME')
+    ? String.fromEnvironment('FLUTTER_BUILD_NAME')
+    : null;
+
+/// The build number compiled into the running bundle, see
+/// [_compileTimeBuildName].
+const String? _compileTimeBuildNumber =
+    bool.hasEnvironment('FLUTTER_BUILD_NUMBER')
+    ? String.fromEnvironment('FLUTTER_BUILD_NUMBER')
+    : null;
+
 /// The web implementation of [PackageInfoPlatform].
 ///
 /// This class implements the `package:package_info_plus` functionality for the web.
 class PackageInfoPlusWebPlugin extends PackageInfoPlatform {
   final Client? _client;
   final AssetManager _assetManager;
-
-  /// Create plugin with http client and asset manager for testing purposes.
-  PackageInfoPlusWebPlugin([this._client, AssetManager? assetManagerMock])
-    : _assetManager = assetManagerMock ?? assetManager;
+  final String? _buildName;
+  final String? _buildNumber;
+
+  /// Create plugin with http client, asset manager and compile-time build
+  /// name and number for testing purposes.
+  PackageInfoPlusWebPlugin([
+    this._client,
+    AssetManager? assetManagerMock,
+    this._buildName = _compileTimeBuildName,
+    this._buildNumber = _compileTimeBuildNumber,
+  ]) : _assetManager = assetManagerMock ?? assetManager;
 
   /// Registers this class as the default instance of [PackageInfoPlatform].
   static void registerWith(Registrar registrar) {
@@ -64,8 +87,13 @@ class PackageInfoPlusWebPlugin extends PackageInfoPlatform {
 
     return PackageInfoData(
       appName: versionMap['app_name'] ?? '',
-      version: versionMap['version'] ?? '',
-      buildNumber: versionMap['build_number'] ?? '',
+      // `version.json` describes the deployed bundle, which differs from the
+      // running one when the client is stale, so prefer the compile-time
+      // version embedded in the running bundle.
+      version: _buildName ?? versionMap['version'] ?? '',
+      buildNumber: _buildName != null
+          ? _buildNumber ?? ''
+          : versionMap['build_number'] ?? '',
       packageName: versionMap['package_name'] ?? '',
       // will remain empty on web
       buildSignature: '',