anchor.diff:  /// The active task backend service.
   TaskBackend get taskBackend => ss.lookup(#_taskBackend) as TaskBackend;
   
  -/// Packages that are allow listed for initial testing of task backend.
  -final _allowListedPackages = [
  -  // Few small packages
  -  'retry',
  -  'pem',
  -  'http',
  -  'collection',
  -  'meta',
  -  'path',
  -  'canonical_json',
  -  'slugid',
  -  // Packages owned by the Dart team
  -  '_fe_analyzer_shared',
  -  'analyzer',
  -  'analyzer_plugin',
  -  'appengine',
  -  'args',
  -  'async',
  -  'bazel_worker',
  -  'benchmark_harness',
  -  'boolean_selector',
  -  'browser_launcher',
  -  'build',
  -  'build_config',
  -  'build_daemon',
  -  'build_modules',
  -  'build_resolvers',
  -  'build_runner',
  -  'build_runner_core',
  -  'build_test',
  -  'build_vm_compilers',
  -  'build_web_compilers',
  -  'characters',
  -  'cli_util',
  -  'clock',
  -  'code_builder',
  -  'collection',
  -  'convert',
  -  'coverage',
  -  'cronet_http',
  -  'crypto',
  -  'csslib',
  -  'cupertino_http',
  -  'dart_flutter_team_lints',
  -  'dart_internal',
  -  'dart_style',
  -  'dartdoc',
  -  'dds',
  -  'dds_service_extensions',
  -  'dwds',
  -  'fake_async',
  -  'ffi',
  -  'ffigen',
  -  'fixnum',
  -  'frontend_server_client',
  -  'gcloud',
  -  'glob',
  -  'graphs',
  -  'grpc_cronet',
  -  'html',
  -  'http',
  -  'http2',
  -  'http_multi_server',
  -  'http_parser',
  -  'intl',
  -  'intl_translation',
  -  'io',
  -  'jni',
  -  'jnigen',
  -  'js',
  -  'json_rpc_2',
  -  'leak_tracker',
  -  'linter',
  -  'lints',
  -  'logging',
  -  'markdown',
  -  'matcher',
  -  'meta',
  -  'mime',
  -  'mockito',
  -  'native_stack_traces',
  -  'oauth2',
  -  'os_detect',
  -  'package_config',
  -  'pana',
  -  'path',
  -  'pool',
  -  'pub_semver',
  -  'pubspec_parse',
  -  'scratch_space',
  -  'shelf',
  -  'shelf_packages_handler',
  -  'shelf_proxy',
  -  'shelf_router',
  -  'shelf_router_generator',
  -  'shelf_static',
  -  'shelf_test_handler',
  -  'shelf_web_socket',
  -  'source_gen',
  -  'source_map_stack_trace',
  -  'source_maps',
  -  'source_span',
  -  'sse',
  -  'stack_trace',
  -  'stream_channel',
  -  'stream_transform',
  -  'string_scanner',
  -  'term_glyph',
  -  'test',
  -  'test_api',
  -  'test_core',
  -  'test_descriptor',
  -  'test_process',
  -  'test_reflective_loader',
  -  'timing',
  -  'typed_data',
  -  'usage',
  -  'vm_service',
  -  'vm_snapshot_analysis',
  -  'wasm',
  -  'watcher',
  -  'web_socket_channel',
  -  'webdev',
  -  'yaml',
  -  'yaml_edit',
  -];
  -
   class TaskBackend {
     final DatastoreDB _db;
     final CloudCompute _cloudCompute;
  
positive.code: import 'package:pub_dev/package/models.dart';
  import 'package:pub_dev/package/upload_signer_service.dart';
  import 'package:pub_dev/shared/datastore.dart';
  import 'package:pub_dev/shared/env_config.dart';
  import 'package:pub_dev/shared/exceptions.dart';
  import 'package:pub_dev/shared/redis_cache.dart' show cache;
  import 'package:pub_dev/shared/utils.dart' show canonicalizeVersion;
  
negative.code:     String packageName, {
      bool updateDependants = false,
    }) async {
      var lastVersionCreated = initialTimestamp;
      await withRetryTransaction(_db, (tx) async {
        final pkgKey = _db.emptyKey.append(Package, id: packageName);
  