Flutter Web - Runtime Docker variables - prepare_app_to_start

prepare_app_to_start.dart

// Compose app version by adding build_number and environment type
final versionJsonFile = File(versionJsonPath);
final versionJson = jsonDecode(await versionJsonFile.readAsString());
final appVersion = '${versionJson['version']}b${versionJson['build_number']}${appEnvironment[0]}'.trim();

// Save environment json file
final envFile = File(envJsonPath);
final envFileContent = const JsonEncoder.withIndent('    ').convert(envJson);
final envFileMd5 = md5.convert(utf8.encode(envFileContent)).toString();
await envFile.writeAsString(envFileContent);

* * * 

// Update flutter_service_worker.js file by specifying environment.json MD5 hash
final workerJsFile = File(workerJsPath);
final workerJsContent = await workerJsFile.readAsString();
final workerJsReplaced = workerJsContent.replaceAll(
  RegExp('"assets/asset/$envFileName": "[0-9a-f]{32}"'),
  '"assets/asset/$envFileName": "$envFileMd5"',
);
await workerJsFile.writeAsString(workerJsReplaced);