[web] Change the web server to support path url strategy (#66606)

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

@@ -190,6 +190,7 @@ class WebAssetServer implements AssetReader {
           platform: globals.platform,
           flutterRoot: Cache.flutterRoot,
           webBuildDirectory: getWebBuildDirectory(),
+          basePath: server.basePath,
         );
         shelf.serveRequests(httpServer, releaseAssetServer.handle);
         return server;
@@ -316,30 +317,28 @@ class WebAssetServer implements AssetReader {
   @visibleForTesting
   Uint8List getMetadata(String path) => _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 {
-    String requestPath = request.url.path;
-    while (requestPath.startsWith('/')) {
-      requestPath = requestPath.substring(1);
+    final String requestPath = _stripBasePath(request.url.path, basePath);
+
+    if (requestPath == null) {
+      return shelf.Response.notFound('');
     }
-    final Map<String, String> headers = <String, String>{};
+
     // If the response is `/`, then we are requesting the index file.
-    if (request.url.path == '/' || request.url.path.isEmpty) {
-      final File indexFile = globals.fs.currentDirectory
-        .childDirectory('web')
-        .childFile('index.html');
-      if (indexFile.existsSync()) {
-        headers[HttpHeaders.contentTypeHeader] = 'text/html';
-        headers[HttpHeaders.contentLengthHeader] = indexFile.lengthSync().toString();
-        return shelf.Response.ok(indexFile.openRead(), headers: headers);
-      } else {
-        headers[HttpHeaders.contentTypeHeader] = 'text/html';
-        headers[HttpHeaders.contentLengthHeader] = _kDefaultIndex.length.toString();
-        return shelf.Response.ok(_kDefaultIndex, headers: headers);
-      }
+    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';
@@ -407,7 +406,7 @@ class WebAssetServer implements AssetReader {
     }
 
     if (!file.existsSync()) {
-      return shelf.Response.notFound('');
+      return _serveIndex();
     }
 
     // For real files, use a serialized file stat plus path as a revision.
@@ -536,6 +535,23 @@ class WebAssetServer implements AssetReader {
   /// Whether to use the cavaskit SDK for rendering.
   bool canvasKitRendering = false;
 
+  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()) {
+      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.
@@ -907,6 +923,7 @@ class ReleaseAssetServer {
     @required String webBuildDirectory,
     @required String flutterRoot,
     @required Platform platform,
+    this.basePath = '',
   }) : _fileSystem = fileSystem,
        _platform = platform,
        _flutterRoot = flutterRoot,
@@ -920,6 +937,12 @@ class ReleaseAssetServer {
   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,
@@ -931,11 +954,17 @@ class ReleaseAssetServer {
 
   Future<shelf.Response> handle(shelf.Request request) async {
     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(request.url.path);
+        final Uri potential = uri.resolve(requestPath);
         if (potential == null || !_fileSystem.isFileSync(
           potential.toFilePath(windows: _platform.isWindows))) {
           continue;
@@ -955,13 +984,11 @@ class ReleaseAssetServer {
         'Content-Type': mimeType,
       });
     }
-    if (request.url.path == '') {
-      final File file = _fileSystem.file(_fileSystem.path.join(_webBuildDirectory, 'index.html'));
-      return shelf.Response.ok(file.readAsBytesSync(), headers: <String, String>{
-        'Content-Type': 'text/html',
-      });
-    }
-    return shelf.Response.notFound('');
+
+    final File file = _fileSystem.file(_fileSystem.path.join(_webBuildDirectory, 'index.html'));
+    return shelf.Response.ok(file.readAsBytesSync(), headers: <String, String>{
+      'Content-Type': 'text/html',
+    });
   }
 }
 
@@ -975,3 +1002,19 @@ Future<Directory> _loadDwdsDirectory(FileSystem fileSystem, Logger logger) async
   );
   return fileSystem.directory(packageConfig['dwds'].packageUriRoot);
 }
+
+String _stripBasePath(String path, String basePath) {
+  while (path.startsWith('/')) {
+    path = path.substring(1);
+  }
+  if (path.startsWith(basePath)) {
+    path = path.substring(basePath.length);
+  } else {
+    // The given path isn't under base path, return null to indicate that.
+    return null;
+  }
+  while (path.startsWith('/')) {
+    path = path.substring(1);
+  }
+  return path;
+}

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

@@ -160,6 +160,61 @@ void main() {
     expect((await response.read().toList()).first, source.readAsBytesSync());
   }));
 
+  test('takes base path into account when serving', () => testbed.run(() async {
+    webAssetServer.basePath = 'base/path';
+
+    globals.fs.file('foo.png').createSync();
+    globals.fs.currentDirectory = globals.fs.directory('project_directory')
+      ..createSync();
+
+    final File source = globals.fs.file(globals.fs.path.join('web', 'foo.png'))
+      ..createSync(recursive: true)
+      ..writeAsBytesSync(kTransparentImage);
+    final Response response =
+      await webAssetServer.handleRequest(
+        Request('GET', Uri.parse('http://foobar/base/path/foo.png')),
+      );
+
+    expect(response.headers, allOf(<Matcher>[
+      containsPair(HttpHeaders.contentLengthHeader, source.lengthSync().toString()),
+      containsPair(HttpHeaders.contentTypeHeader, 'image/png'),
+      containsPair(HttpHeaders.etagHeader, isNotNull),
+      containsPair(HttpHeaders.cacheControlHeader, 'max-age=0, must-revalidate')
+    ]));
+    expect((await response.read().toList()).first, source.readAsBytesSync());
+  }));
+
+  test('serves index.html at the base path', () => testbed.run(() async {
+    webAssetServer.basePath = 'base/path';
+
+    const String htmlContent = '<html><head></head><body id="test"></body></html>';
+    final Directory webDir = globals.fs.currentDirectory
+      .childDirectory('web')
+      ..createSync();
+    webDir.childFile('index.html').writeAsStringSync(htmlContent);
+
+    final Response response = await webAssetServer
+      .handleRequest(Request('GET', Uri.parse('http://foobar/base/path/')));
+
+    expect(response.statusCode, HttpStatus.ok);
+    expect(await response.readAsString(), htmlContent);
+  }));
+
+  test('does not serve outside the base path', () => testbed.run(() async {
+    webAssetServer.basePath = 'base/path';
+
+    const String htmlContent = '<html><head></head><body id="test"></body></html>';
+    final Directory webDir = globals.fs.currentDirectory
+      .childDirectory('web')
+      ..createSync();
+    webDir.childFile('index.html').writeAsStringSync(htmlContent);
+
+    final Response response = await webAssetServer
+      .handleRequest(Request('GET', Uri.parse('http://foobar/')));
+
+    expect(response.statusCode, HttpStatus.notFound);
+  }));
+
   test('serves JavaScript files from in memory cache not from manifest', () => testbed.run(() async {
     webAssetServer.writeFile('foo.js', 'main() {}');
 
@@ -191,25 +246,18 @@ void main() {
     expect(await cachedResponse.read().toList(), isEmpty);
   }));
 
-  test('handles missing JavaScript files from in memory cache', () => testbed.run(() async {
-    final File source = globals.fs.file('source')
-      ..writeAsStringSync('main() {}');
-    final File sourcemap = globals.fs.file('sourcemap')
-      ..writeAsStringSync('{}');
-    final File metadata = globals.fs.file('metadata')
-      ..writeAsStringSync('{}');
-    final File manifest = globals.fs.file('manifest')
-      ..writeAsStringSync(json.encode(<String, Object>{'/foo.js': <String, Object>{
-        'code': <int>[0, source.lengthSync()],
-        'sourcemap': <int>[0, 2],
-        'metadata': <int>[0, 2],
-      }}));
-    webAssetServer.write(source, manifest, sourcemap, metadata);
+  test('serves index.html when path is unknown', () => testbed.run(() async {
+    const String htmlContent = '<html><head></head><body id="test"></body></html>';
+    final Directory webDir = globals.fs.currentDirectory
+      .childDirectory('web')
+      ..createSync();
+    webDir.childFile('index.html').writeAsStringSync(htmlContent);
 
     final Response response = await webAssetServer
-      .handleRequest(Request('GET', Uri.parse('http://foobar/bar.js')));
+      .handleRequest(Request('GET', Uri.parse('http://foobar/bar/baz')));
 
-    expect(response.statusCode, HttpStatus.notFound);
+    expect(response.statusCode, HttpStatus.ok);
+    expect(await response.readAsString(), htmlContent);
   }));
 
   test('serves default index.html', () => testbed.run(() async {
@@ -333,13 +381,6 @@ void main() {
     Platform: () => linux,
   }));
 
-  test('Handles missing Dart files from filesystem', () => testbed.run(() async {
-    final Response response = await webAssetServer
-      .handleRequest(Request('GET', Uri.parse('http://foobar/foo.dart')));
-
-    expect(response.statusCode, HttpStatus.notFound);
-  }));
-
   test('serves asset files from in filesystem with known mime type', () => testbed.run(() async {
     final File source = globals.fs.file(globals.fs.path.join('build', 'flutter_assets', 'foo.png'))
       ..createSync(recursive: true)
@@ -397,20 +438,6 @@ void main() {
     expect(etag.runes, everyElement(predicate((int char) => char < 255)));
   }));
 
-  test('handles serving missing asset file', () => testbed.run(() async {
-    final Response response = await webAssetServer
-      .handleRequest(Request('GET', Uri.parse('http://foobar/assets/foo')));
-
-    expect(response.statusCode, HttpStatus.notFound);
-  }));
-
-  test('handles serving unresolvable package file', () => testbed.run(() async {
-    final Response response = await webAssetServer
-      .handleRequest(Request('GET', Uri.parse('http://foobar/packages/notpackage/file')));
-
-    expect(response.statusCode, HttpStatus.notFound);
-  }));
-
   test('serves /packages/<package>/<path> files as if they were '
        'package:<package>/<path> uris', () => testbed.run(() async {
     final Uri expectedUri = packages.resolve(