Skip to content

F
Front-End
Switch branch/tag
Find file
BlameHistoryPermalink
devfs_web.dart 37.7 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 
// Copyright 2014 The Flutter 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:async';
import 'dart:typed_data';

import 'package:dwds/data/build_result.dart';
// ignore: import_of_legacy_library_into_null_safe
import 'package:dwds/dwds.dart';
import 'package:html/dom.dart';
import 'package:html/parser.dart';
import 'package:logging/logging.dart' as logging;
import 'package:meta/meta.dart';
import 'package:mime/mime.dart' as mime;
import 'package:package_config/package_config.dart';
import 'package:shelf/shelf.dart' as shelf;
import 'package:shelf/shelf_io.dart' as shelf;
import 'package:vm_service/vm_service.dart' as vm_service;

import '../artifacts.dart';
import '../asset.dart';
import '../base/common.dart';
import '../base/file_system.dart';
import '../base/io.dart';
import '../base/logger.dart';
import '../base/net.dart';
import '../base/platform.dart';
import '../build_info.dart';
import '../build_system/targets/shader_compiler.dart';
import '../build_system/targets/web.dart';
import '../bundle_builder.dart';
import '../cache.dart';
import '../compile.dart';
import '../convert.dart';
import '../dart/package_map.dart';
import '../devfs.dart';
import '../globals.dart' as globals;
import '../project.dart';
import '../vmservice.dart';
import '../web/bootstrap.dart';
import '../web/chrome.dart';
import '../web/compile.dart';
import '../web/file_generators/flutter_js.dart' as flutter_js;
import '../web/memory_fs.dart';
import 'sdk_web_configuration.dart';

typedef DwdsLauncher = Future<Dwds> Function({
  required AssetReader assetReader,
  required Stream<BuildResult> buildResults,
  required ConnectionProvider chromeConnection,
  required LoadStrategy loadStrategy,
  required bool enableDebugging,
  ExpressionCompiler? expressionCompiler,
  bool enableDebugExtension,
  String hostname,
  bool useSseForDebugProxy,
  bool useSseForDebugBackend,
  bool useSseForInjectedClient,
  UrlEncoder? urlEncoder,
  bool spawnDds,
  bool enableDevtoolsLaunch,
  DevtoolsLauncher? devtoolsLauncher,
  bool launchDevToolsInNewWindow,
  SdkConfigurationProvider? sdkConfigurationProvider,
  bool emitDebugEvents,
});

// A minimal index for projects that do not yet support web.
const String _kDefaultIndex = '''
<html>
    <head>
        <base href="/">
    </head>
    <body>
        <script src="main.dart.js"></script>
    </body>
</html>
''';

/// An expression compiler connecting to FrontendServer.
///
/// This is only used in development mode.
class WebExpressionCompiler implements ExpressionCompiler {
  WebExpressionCompiler(this._generator, {
    required FileSystem? fileSystem,
  }) : _fileSystem = fileSystem;

  final ResidentCompiler _generator;
  final FileSystem? _fileSystem;

  @override
  Future<ExpressionCompilationResult> compileExpressionToJs(
    String isolateId,
    String libraryUri,
    int line,
    int column,
    Map<String, String> jsModules,
    Map<String, String> jsFrameValues,
    String moduleName,
    String expression,
  ) async {
    final CompilerOutput? compilerOutput =
        await _generator.compileExpressionToJs(libraryUri, line, column,
            jsModules, jsFrameValues, moduleName, expression);

    if (compilerOutput != null && compilerOutput.outputFilename != null) {
      final String content = utf8.decode(
          _fileSystem!.file(compilerOutput.outputFilename).readAsBytesSync());
      return ExpressionCompilationResult(
          content, compilerOutput.errorCount > 0);
    }

    return ExpressionCompilationResult(
        "InternalError: frontend server failed to compile '$expression'",
        true);
  }

  @override
  Future<void> initialize({String? moduleFormat, bool? soundNullSafety}) async {}

  @override
  Future<bool> updateDependencies(Map<String, ModuleInfo> modules) async => true;
}

/// A web server which handles serving JavaScript and assets.
///
/// This is only used in development mode.
class WebAssetServer implements AssetReader {
  @visibleForTesting
  WebAssetServer(
    this._httpServer,
    this._packages,
    this.internetAddress,
    this._modules,
    this._digests,
    this._nullSafetyMode,
  ) : basePath = _parseBasePathFromIndexHtml(globals.fs.currentDirectory
            .childDirectory('web')
            .childFile('index.html'));

  // Fallback to "application/octet-stream" on null which
  // makes no claims as to the structure of the data.
  static const String _kDefaultMimeType = 'application/octet-stream';

  final Map<String, String> _modules;
  final Map<String, String> _digests;

  int get selectedPort => _httpServer.port;

  void performRestart(List<String> modules) {
    for (final String module in modules) {
      // We skip computing the digest by using the hashCode of the underlying buffer.
      // Whenever a file is updated, the corresponding Uint8List.view it corresponds
      // to will change.
      final String moduleName =
          module.startsWith('/') ? module.substring(1) : module;
      final String name = moduleName.replaceAll('.lib.js', '');
      final String path = moduleName.replaceAll('.js', '');
      _modules[name] = path;
      _digests[name] = _webMemoryFS.files[moduleName].hashCode.toString();
    }
  }

  @visibleForTesting
  List<String> write(
    File codeFile,
    File manifestFile,
    File sourcemapFile,
    File metadataFile,
  ) {
    return _webMemoryFS.write(codeFile, manifestFile, sourcemapFile, metadataFile);
  }

  /// Start the web asset server on a [hostname] and [port].
  ///
  /// If [testMode] is true, do not actually initialize dwds or the shelf static
  /// server.
  ///
  /// Unhandled exceptions will throw a [ToolExit] with the error and stack
  /// trace.
  static Future<WebAssetServer> start(
    ChromiumLauncher? chromiumLauncher,
    String hostname,
    int? port,
    UrlTunneller? urlTunneller,
    bool useSseForDebugProxy,
    bool useSseForDebugBackend,
    bool useSseForInjectedClient,
    BuildInfo buildInfo,
    bool enableDwds,
    bool enableDds,
    Uri entrypoint,
    ExpressionCompiler? expressionCompiler,
    NullSafetyMode nullSafetyMode, {
    bool testMode = false,
    DwdsLauncher dwdsLauncher = Dwds.start,
  }) async {
    InternetAddress address;
    if (hostname == 'any') {
      address = InternetAddress.anyIPv4;
    } else {
      address = (await InternetAddress.lookup(hostname)).first;
    }
    HttpServer? httpServer;
    const int kMaxRetries = 4;
    for (int i = 0; i <= kMaxRetries; i++) {
      try {
        httpServer = await HttpServer.bind(address, port ?? await globals.os.findFreePort());
        break;
      } on SocketException catch (e, s) {
        if (i >= kMaxRetries) {
          globals.printError('Failed to bind web development server:\n$e', stackTrace: s);
          throwToolExit('Failed to bind web development server:\n$e');
        }
        await Future<void>.delayed(const Duration(milliseconds: 100));
      }
    }

    // Allow rendering in a iframe.
    httpServer!.defaultResponseHeaders.remove('x-frame-options', 'SAMEORIGIN');

    final PackageConfig packageConfig = buildInfo.packageConfig;
    final Map<String, String> digests = <String, String>{};
    final Map<String, String> modules = <String, String>{};
    final WebAssetServer server = WebAssetServer(
      httpServer,
      packageConfig,
      address,
      modules,
      digests,
      nullSafetyMode,
    );
    if (testMode) {
      return server;
    }

    // In release builds deploy a simpler proxy server.
    if (buildInfo.mode != BuildMode.debug) {
      final ReleaseAssetServer releaseAssetServer = ReleaseAssetServer(
        entrypoint,
        fileSystem: globals.fs,
        platform: globals.platform,
        flutterRoot: Cache.flutterRoot,
        webBuildDirectory: getWebBuildDirectory(),
        basePath: server.basePath,
      );
      runZonedGuarded(() {
        shelf.serveRequests(httpServer!, releaseAssetServer.handle);
      }, (Object e, StackTrace s) {
        globals.printTrace('Release asset server: error serving requests: $e:$s');
      });
      return server;
    }

    // Return a version string for all active modules. This is populated
    // along with the `moduleProvider` update logic.
    Future<Map<String, String>> digestProvider() async => digests;

    // Ensure dwds is present and provide middleware to avoid trying to
    // load the through the isolate APIs.
    final Directory directory =
        await _loadDwdsDirectory(globals.fs, globals.logger);
    shelf.Handler middleware(FutureOr<shelf.Response> Function(shelf.Request) innerHandler) {
      return (shelf.Request request) async {
        if (request.url.path.endsWith('dwds/src/injected/client.js')) {
          final Uri uri = directory.uri.resolve('src/injected/client.js');
          final String result =
              await globals.fs.file(uri.toFilePath()).readAsString();
          return shelf.Response.ok(result, headers: <String, String>{
            HttpHeaders.contentTypeHeader: 'application/javascript',
          });
        }
        return innerHandler(request);
      };
    }

    logging.Logger.root.level = logging.Level.ALL;
    logging.Logger.root.onRecord.listen(log);

    // In debug builds, spin up DWDS and the full asset server.
    final Dwds dwds = await dwdsLauncher(
      assetReader: server,
      enableDebugExtension: true,
      buildResults: const Stream<BuildResult>.empty(),
      chromeConnection: () async {
        final Chromium chromium = await chromiumLauncher!.connectedInstance;
        return chromium.chromeConnection;
      },
      hostname: hostname,
      urlEncoder: urlTunneller,
      enableDebugging: true,
      useSseForDebugProxy: useSseForDebugProxy,
      useSseForDebugBackend: useSseForDebugBackend,
      useSseForInjectedClient: useSseForInjectedClient,
      loadStrategy: FrontendServerRequireStrategyProvider(
        ReloadConfiguration.none,
        server,
        PackageUriMapper(packageConfig),
        digestProvider,
        server.basePath!,
      ).strategy,
      expressionCompiler: expressionCompiler,
      spawnDds: enableDds,
      sdkConfigurationProvider: SdkWebConfigurationProvider(globals.artifacts!),
    );
    shelf.Pipeline pipeline = const shelf.Pipeline();
    if (enableDwds) {
      pipeline = pipeline.addMiddleware(middleware);
      pipeline = pipeline.addMiddleware(dwds.middleware);
    }
    final shelf.Handler dwdsHandler =
        pipeline.addHandler(server.handleRequest);
    final shelf.Cascade cascade =
        shelf.Cascade().add(dwds.handler).add(dwdsHandler);
    runZonedGuarded(() {
      shelf.serveRequests(httpServer!, cascade.handler);
    }, (Object e, StackTrace s) {
      globals.printTrace('Dwds server: error serving requests: $e:$s');
    });
    server.dwds = dwds;
    server._dwdsInit = true;
    return server;
  }

  final NullSafetyMode _nullSafetyMode;
  final HttpServer _httpServer;
  final WebMemoryFS _webMemoryFS = WebMemoryFS();
  final PackageConfig _packages;
  final InternetAddress internetAddress;
  late final Dwds dwds;
  late Directory entrypointCacheDirectory;
  bool _dwdsInit = false;

  @visibleForTesting
  HttpHeaders get defaultResponseHeaders => _httpServer.defaultResponseHeaders;

  @visibleForTesting
  Uint8List? getFile(String path) => _webMemoryFS.files[path];

  @visibleForTesting
  Uint8List? getSourceMap(String path) => _webMemoryFS.sourcemaps[path];

  @visibleForTesting
  Uint8List? getMetadata(String path) => _webMemoryFS.metadataFiles[path];

  @visibleForTesting

  /// The base path to serve from.
  ///
  /// It should have no leading or trailing slashes.
  String? basePath = '';

  // handle requests for JavaScript source, dart sources maps, or asset files.
  @visibleForTesting
  Future<shelf.Response> handleRequest(shelf.Request request) async {
    if (request.method != 'GET') {
      // Assets are served via GET only.
      return shelf.Response.notFound('');
    }

    final String? requestPath = _stripBasePath(request.url.path, basePath);

    if (requestPath == null) {
      return shelf.Response.notFound('');
    }

    // If the response is `/`, then we are requesting the index file.
    if (requestPath == '/' || requestPath.isEmpty) {
      return _serveIndex();
    }

    final Map<String, String> headers = <String, String>{};

    // Track etag headers for better caching of resources.
    final String? ifNoneMatch = request.headers[HttpHeaders.ifNoneMatchHeader];
    headers[HttpHeaders.cacheControlHeader] = 'max-age=0, must-revalidate';

    // If this is a JavaScript file, it must be in the in-memory cache.
    // Attempt to look up the file by URI.
    final String webServerPath =
        requestPath.replaceFirst('.dart.js', '.dart.lib.js');
    if (_webMemoryFS.files.containsKey(requestPath) || _webMemoryFS.files.containsKey(webServerPath)) {
      final List<int>? bytes = getFile(requestPath) ?? getFile(webServerPath);
      // Use the underlying buffer hashCode as a revision string. This buffer is
      // replaced whenever the frontend_server produces new output files, which
      // will also change the hashCode.
      final String etag = bytes.hashCode.toString();
      if (ifNoneMatch == etag) {
        return shelf.Response.notModified();
      }
      headers[HttpHeaders.contentLengthHeader] = bytes!.length.toString();
      headers[HttpHeaders.contentTypeHeader] = 'application/javascript';
      headers[HttpHeaders.etagHeader] = etag;
      return shelf.Response.ok(bytes, headers: headers);
    }
    // If this is a sourcemap file, then it might be in the in-memory cache.
    // Attempt to lookup the file by URI.
    if (_webMemoryFS.sourcemaps.containsKey(requestPath)) {
      final List<int>? bytes = getSourceMap(requestPath);
      final String etag = bytes.hashCode.toString();
      if (ifNoneMatch == etag) {
        return shelf.Response.notModified();
      }
      headers[HttpHeaders.contentLengthHeader] = bytes!.length.toString();
      headers[HttpHeaders.contentTypeHeader] = 'application/json';
      headers[HttpHeaders.etagHeader] = etag;
      return shelf.Response.ok(bytes, headers: headers);
    }

    // If this is a metadata file, then it might be in the in-memory cache.
    // Attempt to lookup the file by URI.
    if (_webMemoryFS.metadataFiles.containsKey(requestPath)) {
      final List<int>? bytes = getMetadata(requestPath);
      final String etag = bytes.hashCode.toString();
      if (ifNoneMatch == etag) {
        return shelf.Response.notModified();
      }
      headers[HttpHeaders.contentLengthHeader] = bytes!.length.toString();
      headers[HttpHeaders.contentTypeHeader] = 'application/json';
      headers[HttpHeaders.etagHeader] = etag;
      return shelf.Response.ok(bytes, headers: headers);
    }

    File file = _resolveDartFile(requestPath);

    // If all of the lookups above failed, the file might have been an asset.
    // Try and resolve the path relative to the built asset directory.
    if (!file.existsSync()) {
      final Uri potential = globals.fs
          .directory(getAssetBuildDirectory())
          .uri
          .resolve(requestPath.replaceFirst('assets/', ''));
      file = globals.fs.file(potential);
    }

    if (!file.existsSync()) {
      final Uri webPath = globals.fs.currentDirectory
          .childDirectory('web')
          .uri
          .resolve(requestPath);
      file = globals.fs.file(webPath);
    }

    if (!file.existsSync()) {
      // Paths starting with these prefixes should've been resolved above.
      if (requestPath.startsWith('assets/') ||
          requestPath.startsWith('packages/')) {
        return shelf.Response.notFound('');
      }
      return _serveIndex();
    }

    // For real files, use a serialized file stat plus path as a revision.
    // This allows us to update between canvaskit and non-canvaskit SDKs.
    final String etag = file.lastModifiedSync().toIso8601String() +
        Uri.encodeComponent(file.path);
    if (ifNoneMatch == etag) {
      return shelf.Response.notModified();
    }

    final int length = file.lengthSync();
    // Attempt to determine the file's mime type. if this is not provided some
    // browsers will refuse to render images/show video etc. If the tool
    // cannot determine a mime type, fall back to application/octet-stream.
    final String mimeType = mime.lookupMimeType(
        file.path,
        headerBytes: await file.openRead(0, mime.defaultMagicNumbersMaxLength).first,
    ) ?? _kDefaultMimeType;

    headers[HttpHeaders.contentLengthHeader] = length.toString();
    headers[HttpHeaders.contentTypeHeader] = mimeType;
    headers[HttpHeaders.etagHeader] = etag;
    return shelf.Response.ok(file.openRead(), headers: headers);
  }

  /// Tear down the http server running.
  Future<void> dispose() async {
    if (_dwdsInit) {
      await dwds.stop();
    }
    return _httpServer.close();
  }

  /// Write a single file into the in-memory cache.
  void writeFile(String filePath, String contents) {
    writeBytes(filePath, utf8.encode(contents) as Uint8List);
  }

  void writeBytes(String filePath, Uint8List contents) {
    _webMemoryFS.files[filePath] = contents;
  }

  /// Determines what rendering backed to use.
  WebRendererMode webRenderer = WebRendererMode.html;

  shelf.Response _serveIndex() {
    final Map<String, String> headers = <String, String>{
      HttpHeaders.contentTypeHeader: 'text/html',
    };
    final File indexFile = globals.fs.currentDirectory
        .childDirectory('web')
        .childFile('index.html');

    if (indexFile.existsSync()) {
      String indexFileContent =  indexFile.readAsStringSync();
      if (indexFileContent.contains(kBaseHrefPlaceholder)) {
          indexFileContent =  indexFileContent.replaceAll(kBaseHrefPlaceholder, '/');
          headers[HttpHeaders.contentLengthHeader] = indexFileContent.length.toString();
          return shelf.Response.ok(indexFileContent,headers: headers);
        }
      headers[HttpHeaders.contentLengthHeader] =
          indexFile.lengthSync().toString();
      return shelf.Response.ok(indexFile.openRead(), headers: headers);
    }

    headers[HttpHeaders.contentLengthHeader] = _kDefaultIndex.length.toString();
    return shelf.Response.ok(_kDefaultIndex, headers: headers);
  }

  // Attempt to resolve `path` to a dart file.
  File _resolveDartFile(String path) {
    // Return the actual file objects so that local engine changes are automatically picked up.
    switch (path) {
      case 'dart_sdk.js':
        return _resolveDartSdkJsFile;
      case 'dart_sdk.js.map':
        return _resolveDartSdkJsMapFile;
    }
    // This is the special generated entrypoint.
    if (path == 'web_entrypoint.dart') {
      return entrypointCacheDirectory.childFile('web_entrypoint.dart');
    }

    // If this is a dart file, it must be on the local file system and is
    // likely coming from a source map request. The tool doesn't currently
    // consider the case of Dart files as assets.
    final File dartFile =
        globals.fs.file(globals.fs.currentDirectory.uri.resolve(path));
    if (dartFile.existsSync()) {
      return dartFile;
    }

    final List<String> segments = path.split('/');
    if (segments.first.isEmpty) {
      segments.removeAt(0);
    }

    // The file might have been a package file which is signaled by a
    // `/packages/<package>/<path>` request.
    if (segments.first == 'packages') {
      final Uri? filePath = _packages
          .resolve(Uri(scheme: 'package', pathSegments: segments.skip(1)));
      if (filePath != null) {
        final File packageFile = globals.fs.file(filePath);
        if (packageFile.existsSync()) {
          return packageFile;
        }
      }
    }

    // Otherwise it must be a Dart SDK source or a Flutter Web SDK source.
    final Directory dartSdkParent = globals.fs
        .directory(
            globals.artifacts!.getHostArtifact(HostArtifact.engineDartSdkPath))
        .parent;
    final File dartSdkFile = globals.fs.file(dartSdkParent.uri.resolve(path));
    if (dartSdkFile.existsSync()) {
      return dartSdkFile;
    }

    final Directory flutterWebSdk = globals.fs
        .directory(globals.artifacts!.getHostArtifact(HostArtifact.flutterWebSdk));
    final File webSdkFile = globals.fs.file(flutterWebSdk.uri.resolve(path));

    return webSdkFile;
  }

  File get _resolveDartSdkJsFile =>
      globals.fs.file(globals.artifacts!.getHostArtifact(
          kDartSdkJsArtifactMap[webRenderer]![_nullSafetyMode]!
      ));

  File get _resolveDartSdkJsMapFile =>
    globals.fs.file(globals.artifacts!.getHostArtifact(
        kDartSdkJsMapArtifactMap[webRenderer]![_nullSafetyMode]!
    ));

  @override
  Future<String?> dartSourceContents(String serverPath) async {
    serverPath = _stripBasePath(serverPath, basePath)!;
    final File result = _resolveDartFile(serverPath);
    if (result.existsSync()) {
      return result.readAsString();
    }
    return null;
  }

  @override
  Future<String> sourceMapContents(String serverPath) async {
    serverPath = _stripBasePath(serverPath, basePath)!;
    return utf8.decode(_webMemoryFS.sourcemaps[serverPath]!);
  }

  @override
  Future<String?> metadataContents(String serverPath) async {
    final String? resultPath = _stripBasePath(serverPath, basePath);
    if (resultPath == 'main_module.ddc_merged_metadata') {
      return _webMemoryFS.mergedMetadata;
    }
    if (_webMemoryFS.metadataFiles.containsKey(resultPath)) {
      return utf8.decode(_webMemoryFS.metadataFiles[resultPath]!);
    }
    throw Exception('Could not find metadata contents for $serverPath');
  }

  @override
  Future<void> close() async {}
}

class ConnectionResult {
  ConnectionResult(this.appConnection, this.debugConnection, this.vmService);

  final AppConnection? appConnection;
  final DebugConnection? debugConnection;
  final vm_service.VmService vmService;
}

typedef VmServiceFactory = Future<vm_service.VmService> Function(
  Uri, {
  CompressionOptions compression,
  required Logger logger,
});

/// The web specific DevFS implementation.
class WebDevFS implements DevFS {
  /// Create a new [WebDevFS] instance.
  ///
  /// [testMode] is true, do not actually initialize dwds or the shelf static
  /// server.
  WebDevFS({
    required this.hostname,
    required int? port,
    required this.packagesFilePath,
    required this.urlTunneller,
    required this.useSseForDebugProxy,
    required this.useSseForDebugBackend,
    required this.useSseForInjectedClient,
    required this.buildInfo,
    required this.enableDwds,
    required this.enableDds,
    required this.entrypoint,
    required this.expressionCompiler,
    required this.chromiumLauncher,
    required this.nullAssertions,
    required this.nativeNullAssertions,
    required this.nullSafetyMode,
    this.testMode = false,
  }) : _port = port;

  final Uri entrypoint;
  final String hostname;
  final String packagesFilePath;
  final UrlTunneller? urlTunneller;
  final bool useSseForDebugProxy;
  final bool useSseForDebugBackend;
  final bool useSseForInjectedClient;
  final BuildInfo buildInfo;
  final bool enableDwds;
  final bool enableDds;
  final bool testMode;
  final ExpressionCompiler? expressionCompiler;
  final ChromiumLauncher? chromiumLauncher;
  final bool nullAssertions;
  final bool nativeNullAssertions;
  final int? _port;
  final NullSafetyMode nullSafetyMode;

  late WebAssetServer webAssetServer;

  Dwds get dwds => webAssetServer.dwds;

  // A flag to indicate whether we have called `setAssetDirectory` on the target device.
  @override
  bool hasSetAssetDirectory = false;

  @override
  bool didUpdateFontManifest = false;

  Future<DebugConnection>? _cachedExtensionFuture;
  StreamSubscription<void>? _connectedApps;

  /// Connect and retrieve the [DebugConnection] for the current application.
  ///
  /// Only calls [AppConnection.runMain] on the subsequent connections.
  Future<ConnectionResult?> connect(
    bool useDebugExtension, {
    @visibleForTesting
    VmServiceFactory vmServiceFactory = createVmServiceDelegate,
  }) {
    final Completer<ConnectionResult> firstConnection =
        Completer<ConnectionResult>();
    // Note there is an asynchronous gap between this being set to true and
    // [firstConnection] completing; thus test the boolean to determine if
    // the current connection is the first.
    bool foundFirstConnection = false;
    _connectedApps =
        dwds.connectedApps.listen((AppConnection appConnection) async {
      try {
        final DebugConnection debugConnection = useDebugExtension
            ? await (_cachedExtensionFuture ??=
                dwds.extensionDebugConnections.stream.first)
            : await dwds.debugConnection(appConnection);
        if (foundFirstConnection) {
          appConnection.runMain();
        } else {
          foundFirstConnection = true;
          final vm_service.VmService vmService = await vmServiceFactory(
            Uri.parse(debugConnection.uri),
            logger: globals.logger,
          );
          firstConnection
              .complete(ConnectionResult(appConnection, debugConnection, vmService));
        }
      } on Exception catch (error, stackTrace) {
        if (!firstConnection.isCompleted) {
          firstConnection.completeError(error, stackTrace);
        }
      }
    }, onError: (Object error, StackTrace stackTrace) {
      globals.printError(
        'Unknown error while waiting for debug connection:$error\n$stackTrace',
      );
      if (!firstConnection.isCompleted) {
        firstConnection.completeError(error, stackTrace);
      }
    });
    return firstConnection.future;
  }

  @override
  List<Uri> sources = <Uri>[];

  @override
  DateTime? lastCompiled;

  @override
  PackageConfig? lastPackageConfig;

  // We do not evict assets on the web.
  @override
  Set<String> get assetPathsToEvict => const <String>{};

  @override
  Uri? get baseUri => _baseUri;
  Uri? _baseUri;

  @override
  Future<Uri> create() async {
    webAssetServer = await WebAssetServer.start(
      chromiumLauncher,
      hostname,
      _port,
      urlTunneller,
      useSseForDebugProxy,
      useSseForDebugBackend,
      useSseForInjectedClient,
      buildInfo,
      enableDwds,
      enableDds,
      entrypoint,
      expressionCompiler,
      nullSafetyMode,
      testMode: testMode,
    );

    final int selectedPort = webAssetServer.selectedPort;
    if (buildInfo.dartDefines.contains('FLUTTER_WEB_AUTO_DETECT=true')) {
      webAssetServer.webRenderer = WebRendererMode.autoDetect;
    } else if (buildInfo.dartDefines.contains('FLUTTER_WEB_USE_SKIA=true')) {
      webAssetServer.webRenderer = WebRendererMode.canvaskit;
    }
    if (hostname == 'any') {
      _baseUri = Uri.http('localhost:$selectedPort', webAssetServer.basePath!);
    } else {
      _baseUri = Uri.http('$hostname:$selectedPort', webAssetServer.basePath!);
    }
    return _baseUri!;
  }

  @override
  Future<void> destroy() async {
    await webAssetServer.dispose();
    await _connectedApps?.cancel();
  }

  @override
  Uri deviceUriToHostUri(Uri deviceUri) {
    return deviceUri;
  }

  @override
  String get fsName => 'web_asset';

  @override
  Directory? get rootDirectory => null;

  @override
  Future<UpdateFSReport> update({
    required Uri mainUri,
    required ResidentCompiler generator,
    required bool trackWidgetCreation,
    required String pathToReload,
    required List<Uri> invalidatedFiles,
    required PackageConfig packageConfig,
    required String dillOutputPath,
    required DevelopmentShaderCompiler shaderCompiler,
    DevFSWriter? devFSWriter,
    String? target,
    AssetBundle? bundle,
    DateTime? firstBuildTime,
    bool bundleFirstUpload = false,
    bool fullRestart = false,
    String? projectRootPath,
    File? dartPluginRegistrant,
  }) async {
    assert(trackWidgetCreation != null);
    assert(generator != null);
    lastPackageConfig = packageConfig;
    final File mainFile = globals.fs.file(mainUri);
    final String outputDirectoryPath = mainFile.parent.path;

    if (bundleFirstUpload) {
      webAssetServer.entrypointCacheDirectory =
          globals.fs.directory(outputDirectoryPath);
      generator.addFileSystemRoot(outputDirectoryPath);
      final String entrypoint = globals.fs.path.basename(mainFile.path);
      webAssetServer.writeBytes(entrypoint, mainFile.readAsBytesSync());
      webAssetServer.writeBytes('require.js', requireJS.readAsBytesSync());
      webAssetServer.writeBytes(
          'stack_trace_mapper.js', stackTraceMapper.readAsBytesSync());
      webAssetServer.writeFile(
          'manifest.json', '{"info":"manifest not generated in run mode."}');
      webAssetServer.writeFile('flutter.js', flutter_js.generateFlutterJsFile());
      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(
          requireUrl: 'require.js',
          mapperUrl: 'stack_trace_mapper.js',
        ),
      );
      webAssetServer.writeFile(
        'main_module.bootstrap.js',
        generateMainModule(
          entrypoint: entrypoint,
          nullAssertions: nullAssertions,
          nativeNullAssertions: nativeNullAssertions,
        ),
      );
      // TODO(zanderso): refactor the asset code in this and the regular devfs to
      // be shared.
      if (bundle != null) {
        await writeBundle(
          globals.fs.directory(getAssetBuildDirectory()),
          bundle.entries,
          bundle.entryKinds,
        );
      }
    }
    final DateTime candidateCompileTime = DateTime.now();
    if (fullRestart) {
      generator.reset();
    }

    // The tool generates an entrypoint file in a temp directory to handle
    // the web specific bootstrap logic. To make it easier for DWDS to handle
    // mapping the file name, this is done via an additional file root and
    // special hard-coded scheme.
    final CompilerOutput? compilerOutput = await generator.recompile(
      Uri(
        scheme: 'org-dartlang-app',
        path: '/${mainUri.pathSegments.last}',
      ),
      invalidatedFiles,
      outputPath: dillOutputPath,
      packageConfig: packageConfig,
      projectRootPath: projectRootPath,
      fs: globals.fs,
      dartPluginRegistrant: dartPluginRegistrant,
    );
    if (compilerOutput == null || compilerOutput.errorCount > 0) {
      return UpdateFSReport();
    }

    // Only update the last compiled time if we successfully compiled.
    lastCompiled = candidateCompileTime;
    // list of sources that needs to be monitored are in [compilerOutput.sources]
    sources = compilerOutput.sources;
    late File codeFile;
    File manifestFile;
    File sourcemapFile;
    File metadataFile;
    late List<String> modules;
    try {
      final Directory parentDirectory = globals.fs.directory(outputDirectoryPath);
      codeFile = parentDirectory.childFile('${compilerOutput.outputFilename}.sources');
      manifestFile = parentDirectory.childFile('${compilerOutput.outputFilename}.json');
      sourcemapFile = parentDirectory.childFile('${compilerOutput.outputFilename}.map');
      metadataFile = parentDirectory.childFile('${compilerOutput.outputFilename}.metadata');
      modules = webAssetServer._webMemoryFS.write(codeFile, manifestFile, sourcemapFile, metadataFile);
    } on FileSystemException catch (err) {
      throwToolExit('Failed to load recompiled sources:\n$err');
    }
    webAssetServer.performRestart(modules);
    return UpdateFSReport(
      success: true,
      syncedBytes: codeFile.lengthSync(),
      invalidatedSourcesCount: invalidatedFiles.length,
    );
  }

  @visibleForTesting
  final File requireJS = globals.fs.file(globals.fs.path.join(
    globals.artifacts!.getHostArtifact(HostArtifact.engineDartSdkPath).path,
    'lib',
    'dev_compiler',
    'kernel',
    'amd',
    'require.js',
  ));

  @visibleForTesting
  final File stackTraceMapper = globals.fs.file(globals.fs.path.join(
    globals.artifacts!.getHostArtifact(HostArtifact.engineDartSdkPath).path,
    'lib',
    'dev_compiler',
    'web',
    'dart_stack_trace_mapper.js',
  ));

  @override
  void resetLastCompiled() {
    // Not used for web compilation.
  }

  @override
  Set<String> get shaderPathsToEvict => <String>{};
}

class ReleaseAssetServer {
  ReleaseAssetServer(
    this.entrypoint, {
    required FileSystem fileSystem,
    required String? webBuildDirectory,
    required String? flutterRoot,
    required Platform platform,
    this.basePath = '',
  })  : _fileSystem = fileSystem,
        _platform = platform,
        _flutterRoot = flutterRoot,
        _webBuildDirectory = webBuildDirectory,
        _fileSystemUtils =
            FileSystemUtils(fileSystem: fileSystem, platform: platform);

  final Uri entrypoint;
  final String? _flutterRoot;
  final String? _webBuildDirectory;
  final FileSystem _fileSystem;
  final FileSystemUtils _fileSystemUtils;
  final Platform _platform;

  @visibleForTesting

  /// The base path to serve from.
  ///
  /// It should have no leading or trailing slashes.
  final String? basePath;

  // Locations where source files, assets, or source maps may be located.
  List<Uri> _searchPaths() => <Uri>[
        _fileSystem.directory(_webBuildDirectory).uri,
        _fileSystem.directory(_flutterRoot).uri,
        _fileSystem.directory(_flutterRoot).parent.uri,
        _fileSystem.currentDirectory.uri,
        _fileSystem.directory(_fileSystemUtils.homeDirPath).uri,
      ];

  Future<shelf.Response> handle(shelf.Request request) async {
    if (request.method != 'GET') {
      // Assets are served via GET only.
      return shelf.Response.notFound('');
    }

    Uri? fileUri;
    final String? requestPath = _stripBasePath(request.url.path, basePath);

    if (requestPath == null) {
      return shelf.Response.notFound('');
    }

    if (request.url.toString() == 'main.dart') {
      fileUri = entrypoint;
    } else {
      for (final Uri uri in _searchPaths()) {
        final Uri potential = uri.resolve(requestPath);
        if (potential == null ||
            !_fileSystem.isFileSync(
                potential.toFilePath(windows: _platform.isWindows))) {
          continue;
        }
        fileUri = potential;
        break;
      }
    }
    if (fileUri != null) {
      final File file = _fileSystem.file(fileUri);
      final Uint8List bytes = file.readAsBytesSync();
      // Fallback to "application/octet-stream" on null which
      // makes no claims as to the structure of the data.
      final String mimeType =
          mime.lookupMimeType(file.path, headerBytes: bytes) ??
              'application/octet-stream';
      return shelf.Response.ok(bytes, headers: <String, String>{
        'Content-Type': mimeType,
      });
    }

    final File file = _fileSystem
        .file(_fileSystem.path.join(_webBuildDirectory!, 'index.html'));
    return shelf.Response.ok(file.readAsBytesSync(), headers: <String, String>{
      'Content-Type': 'text/html',
    });
  }
}

@visibleForTesting
void log(logging.LogRecord event) {
  final String error = event.error == null? '': 'Error: ${event.error}';
  if (event.level >= logging.Level.SEVERE) {
    globals.printError('${event.loggerName}: ${event.message}$error', stackTrace: event.stackTrace);
  } else if (event.level == logging.Level.WARNING) {
    // Note: Temporary fix for https://github.com/flutter/flutter/issues/109792
    // TODO(annagrin): Remove the condition after the bogus warning is
    // removed in dwds: https://github.com/dart-lang/webdev/issues/1722
    if (!event.message.contains('No module for')) {
      globals.printWarning('${event.loggerName}: ${event.message}$error');
    }
  } else  {
    globals.printTrace('${event.loggerName}: ${event.message}$error');
  }
}

Future<Directory> _loadDwdsDirectory(
    FileSystem fileSystem, Logger logger) async {
  final String toolPackagePath =
      fileSystem.path.join(Cache.flutterRoot!, 'packages', 'flutter_tools');
  final String packageFilePath =
      fileSystem.path.join(toolPackagePath, '.dart_tool', 'package_config.json');
  final PackageConfig packageConfig = await loadPackageConfigWithLogging(
    fileSystem.file(packageFilePath),
    logger: logger,
  );
  return fileSystem.directory(packageConfig['dwds']!.packageUriRoot);
}

String? _stripBasePath(String path, String? basePath) {
  path = _stripLeadingSlashes(path);
  if (basePath != null && path.startsWith(basePath)) {
    path = path.substring(basePath.length);
  } else {
    // The given path isn't under base path, return null to indicate that.
    return null;
  }
  return _stripLeadingSlashes(path);
}

String _stripLeadingSlashes(String path) {
  while (path.startsWith('/')) {
    path = path.substring(1);
  }
  return path;
}

String _stripTrailingSlashes(String path) {
  while (path.endsWith('/')) {
    path = path.substring(0, path.length - 1);
  }
  return path;
}

String? _parseBasePathFromIndexHtml(File indexHtml) {
  final String htmlContent =
      indexHtml.existsSync() ? indexHtml.readAsStringSync() : _kDefaultIndex;
  final Document document = parse(htmlContent);
  final Element? baseElement = document.querySelector('base');
  String? baseHref =
      baseElement?.attributes == null ? null : baseElement!.attributes['href'];

  if (baseHref == null || baseHref == kBaseHrefPlaceholder) {
    baseHref = '';
  } else if (!baseHref.startsWith('/')) {
    throw ToolExit(
      'Error: The base href in "web/index.html" must be absolute (i.e. start '
      'with a "/"), but found: `${baseElement!.outerHtml}`.\n'
      '$basePathExample',
    );
  } else if (!baseHref.endsWith('/')) {
    throw ToolExit(
      'Error: The base href in "web/index.html" must end with a "/", but found: `${baseElement!.outerHtml}`.\n'
      '$basePathExample',
    );
  } else {
    baseHref = _stripLeadingSlashes(_stripTrailingSlashes(baseHref));
  }

  return baseHref;
}

const String basePathExample = '''
For example, to serve from the root use:

    <base href="/">

To serve from a subpath "foo" (i.e. http://localhost:8080/foo/ instead of http://localhost:8080/) use:

    <base href="/foo/">

For more information, see: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/base
''';

HIAST - GitLab