[flutter_tools] generates version.json for web using flutter tool (#64644)

Generates version.json in web directory of project. version.json can be used in the future version of package_info which will support web. version.json has the following keys : app_name, version and build_number. This file is generated every time a user runs or builds the project.
Co-authored-by: Jonah Williams <jonahwilliams@google.com>

packages/flutter_tools/lib/src/build_runner/devfs_web.dart

@@ -30,6 +30,7 @@ import '../convert.dart';
 import '../dart/package_map.dart';
 import '../devfs.dart';
 import '../globals.dart' as globals;
+import '../project.dart';
 import '../web/bootstrap.dart';
 import '../web/chrome.dart';
 
@@ -788,6 +789,7 @@ class WebDevFS implements DevFS {
       webAssetServer.writeBytes('stack_trace_mapper.js', stackTraceMapper.readAsBytesSync());
       webAssetServer.writeFile('manifest.json', '{"info":"manifest not generated in run mode."}');
       webAssetServer.writeFile('flutter_service_worker.js', '// Service worker not loaded in run mode.');
+      webAssetServer.writeFile('version.json', FlutterProject.current().getVersionInfo());
       webAssetServer.writeFile(
         'main.dart.js',
         generateBootstrapScript(

packages/flutter_tools/lib/src/build_system/targets/web.dart

@@ -14,6 +14,7 @@ import '../../base/io.dart';
 import '../../build_info.dart';
 import '../../dart/package_map.dart';
 import '../../globals.dart' as globals;
+import '../../project.dart';
 import '../build_system.dart';
 import '../depfile.dart';
 import 'assets.dart';
@@ -295,6 +296,11 @@ class WebReleaseBundle extends Target {
         environment.outputDir.childFile(globals.fs.path.basename(outputFile.path)).path
       );
     }
+
+    final String versionInfo = FlutterProject.current().getVersionInfo();
+    environment.outputDir
+        .childFile('version.json')
+        .writeAsStringSync(versionInfo);
     final Directory outputDirectory = environment.outputDir.childDirectory('assets');
     outputDirectory.createSync(recursive: true);
     final Depfile depfile = await copyAssets(

packages/flutter_tools/lib/src/project.dart

@@ -8,6 +8,7 @@ import 'package:meta/meta.dart';
 import 'package:xml/xml.dart';
 import 'package:yaml/yaml.dart';
 
+import '../src/convert.dart';
 import 'android/gradle_utils.dart' as gradle;
 import 'artifacts.dart';
 import 'base/common.dart';
@@ -263,6 +264,16 @@ class FlutterProject {
     }
     await injectPlugins(this, checkProjects: checkProjects);
   }
+
+  /// Returns a json encoded string containing the [appName], [version], and [buildNumber] that is used to generate version.json
+  String getVersionInfo()  {
+    final Map<String, String> versionFileJson = <String, String>{
+      'app_name': manifest.appName,
+      'version': manifest.buildName,
+      'build_number': manifest.buildNumber
+    };
+    return jsonEncode(versionFileJson);
+  }
 }
 
 /// Base class for projects per platform.

packages/flutter_tools/test/general.shard/build_system/targets/web_test.dart

@@ -92,6 +92,17 @@ void main() {
     expect(generated, contains("import 'package:foo/main.dart' as entrypoint;"));
   }));
 
+  test('version.json is created after release build', () => testbed.run(() async {
+    environment.defines[kBuildMode] = 'release';
+    final Directory webResources = environment.projectDir.childDirectory('web');
+    webResources.childFile('index.html')
+        .createSync(recursive: true);
+    environment.buildDir.childFile('main.dart.js').createSync();
+    await const WebReleaseBundle().build(environment);
+
+    expect(environment.outputDir.childFile('version.json'), exists);
+  }));
+
   test('WebReleaseBundle copies dart2js output and resource files to output directory', () => testbed.run(() async {
     environment.defines[kBuildMode] = 'release';
     final Directory webResources = environment.projectDir.childDirectory('web');

packages/flutter_tools/test/general.shard/project_test.dart

@@ -11,6 +11,7 @@ import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/cache.dart';
+import 'package:flutter_tools/src/convert.dart';
 import 'package:flutter_tools/src/features.dart';
 import 'package:flutter_tools/src/flutter_manifest.dart';
 import 'package:flutter_tools/src/ios/plist_parser.dart';
@@ -241,6 +242,19 @@ void main() {
         expectExists(pluginRegistrantClasses.childFile('GeneratedPluginRegistrant.h'));
         expectExists(pluginRegistrantClasses.childFile('GeneratedPluginRegistrant.m'));
       });
+
+      testUsingContext('Version.json info is correct', (){
+        final MemoryFileSystem fileSystem = MemoryFileSystem.test();
+        final FlutterManifest manifest = FlutterManifest.createFromString('''
+    name: test
+    version: 1.0.0+3
+    ''', logger: BufferLogger.test());
+        final FlutterProject project = FlutterProject(fileSystem.systemTempDirectory,manifest,manifest);
+        final dynamic versionInfo = jsonDecode(project.getVersionInfo());
+        expect(versionInfo['app_name'],'test');
+        expect(versionInfo['version'],'1.0.0');
+        expect(versionInfo['build_number'],'3');
+      });
     });
 
     group('module status', () {

packages/flutter_tools/test/general.shard/web/devfs_web_test.dart

@@ -520,6 +520,7 @@ void main() {
     expect(webDevFS.webAssetServer.getFile('main.dart'), isNotNull);
     expect(webDevFS.webAssetServer.getFile('manifest.json'), isNotNull);
     expect(webDevFS.webAssetServer.getFile('flutter_service_worker.js'), isNotNull);
+    expect(webDevFS.webAssetServer.getFile('version.json'),isNotNull);
     expect(await webDevFS.webAssetServer.dartSourceContents('dart_sdk.js'), 'HELLO');
     expect(await webDevFS.webAssetServer.dartSourceContents('dart_sdk.js.map'), 'THERE');
 
@@ -633,6 +634,7 @@ void main() {
     expect(webDevFS.webAssetServer.getFile('main.dart'), isNotNull);
     expect(webDevFS.webAssetServer.getFile('manifest.json'), isNotNull);
     expect(webDevFS.webAssetServer.getFile('flutter_service_worker.js'), isNotNull);
+    expect(webDevFS.webAssetServer.getFile('version.json'), isNotNull);
     expect(await webDevFS.webAssetServer.dartSourceContents('dart_sdk.js'), 'HELLO');
     expect(await webDevFS.webAssetServer.dartSourceContents('dart_sdk.js.map'), 'THERE');