Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/polymer/src/mirror_loader.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Contains logic to initialize polymer apps during development. This
+/// implementation uses dart:mirrors to load each library as they are discovered
+/// through HTML imports. This is only meant to be during development in
+/// dartium, and the polymer transformers replace this implementation with
+/// codege generation in the polymer-build steps.
+library polymer.src.mirror_loader;
+
+import 'dart:async';
+import 'dart:html';
+import 'dart:collection' show LinkedHashMap;
+
+// Technically, we shouldn't need any @MirrorsUsed, since this is for
+// development only, but our test bots don't yet run pub-build. See more details
+// on the comments of the mirrors import in `lib/polymer.dart`.
+@MirrorsUsed(metaTargets:
+    const [CustomTag, InitMethodAnnotation],
+    override: const ['smoke.mirrors', 'polymer.src.mirror_loader'])
+import 'dart:mirrors';
+
+import 'package:logging/logging.dart' show Logger;
+import 'package:observe/src/dirty_check.dart';
+import 'package:polymer/polymer.dart';
+
+
+/// Used by code generated from the experimental polymer bootstrap in boot.js.
+void startPolymerInDevelopment(List<String> librariesToLoad) {
+  dirtyCheckZone()..run(() {
+    startPolymer(discoverInitializers(librariesToLoad), false);
+  });
+}
+
+/// Set of initializers that are invoked by `initPolymer`.  This is computed the
+/// list by crawling HTML imports, searching for script tags, and including an
+/// initializer for each type tagged with a [CustomTag] annotation and for each
+/// top-level method annotated with [initMethod].
+List<Function> initializers = discoverInitializers(
+    discoverLibrariesToLoad(document, window.location.href));
+
+/// True if we're in deployment mode.
+bool deployMode = false;
+
+/// Discovers what script tags are loaded from HTML pages and collects the
+/// initializers of their corresponding libraries.
+// Visible for testing only.
+List<Function> discoverInitializers(Iterable<String> librariesToLoad) {
+  var initializers = [];
+  for (var lib in librariesToLoad) {
+    try {
+      _loadLibrary(lib, initializers);
+    } catch (e, s) {
+      // Deliver errors async, so if a single library fails it doesn't prevent
+      // other things from loading.
+      new Completer().completeError(e, s);
+    }
+  }
+  return initializers;
+}
+
+/// Walks the HTML import structure to discover all script tags that are
+/// implicitly loaded. This code is only used in Dartium and should only be
+/// called after all HTML imports are resolved. Polymer ensures this by asking
+/// users to put their Dart script tags after all HTML imports (this is checked
+/// by the linter, and Dartium will otherwise show an error message).
+Iterable<_ScriptInfo> _discoverScripts(
+    Document doc, String baseUri, [_State state]) {
+  if (state == null) state = new _State();
+  if (doc == null) {
+    print('warning: $baseUri not found.');
+    return state.scripts.values;
+  }
+  if (!state.seen.add(doc)) return state.scripts.values;
+
+  for (var node in doc.querySelectorAll('script,link[rel="import"]')) {
+    if (node is LinkElement) {
+      _discoverScripts(node.import, node.href, state);
+    } else if (node is ScriptElement && node.type == 'application/dart') {
+      var info = _scriptInfoFor(node, baseUri);
+      if (state.scripts.containsKey(info.resolvedUrl)) {
+        print('warning: Script `${info.resolvedUrl}` included more than once. '
+            'See http://goo.gl/5HPeuP#polymer_44 for more details.');
+      } else {
+        state.scripts[info.resolvedUrl] = info;
+      }
+    }
+  }
+  return state.scripts.values;
+}
+
+/// Internal state used in [_discoverScripts].
+class _State {
+  /// Documents that we have visited thus far.
+  final Set<Document> seen = new Set();
+
+  /// Scripts that have been discovered, in tree order.
+  final LinkedHashMap<String, _ScriptInfo> scripts = {};
+}
+
+/// Holds information about a Dart script tag.
+class _ScriptInfo {
+  /// The original URL seen in the tag fully resolved.
+  final String resolvedUrl;
+
+  /// Whether there was no URL, but code inlined instead.
+  bool get isInline => text != null;
+
+  /// Whether it seems to be a 'package:' URL (starts with the package-root).
+  bool get isPackage => packageUrl != null;
+
+  /// The equivalent 'package:' URL, if any.
+  final String packageUrl;
+
+  /// The inlined text, if any.
+  final String text;
+
+  /// Returns a base64 `data:` uri with the contents of [text].
+  // TODO(sigmund): change back to application/dart: using text/javascript seems
+  // wrong but it hides a warning in Dartium (dartbug.com/18000).
+  String get dataUrl => 'data:text/javascript;base64,${window.btoa(text)}';
+
+  /// URL to import the contents of the original script from Dart. This is
+  /// either the source URL if the script tag had a `src` attribute, or a base64
+  /// encoded `data:` URL if the script contents are inlined, or a `package:`
+  /// URL if the script can be resolved via a package URL.
+  String get importUrl =>
+      isInline ? dataUrl : (isPackage ? packageUrl : resolvedUrl);
+
+  _ScriptInfo(this.resolvedUrl, {this.packageUrl, this.text});
+}
+
+
+// TODO(sigmund): explore other (cheaper) ways to resolve URIs relative to the
+// root library (see dartbug.com/12612)
+final _rootUri = currentMirrorSystem().isolate.rootLibrary.uri;
+
+/// Returns [_ScriptInfo] for [script] which was seen in [baseUri].
+_ScriptInfo _scriptInfoFor(script, baseUri) {
+  var uriString = script.src;
+  if (uriString != '') {
+    var uri = _rootUri.resolve(uriString);
+    if (!_isHttpStylePackageUrl(uri)) return new _ScriptInfo('$uri');
+    // Use package: urls if available. This rule here is more permissive than
+    // how we translate urls in polymer-build, but we expect Dartium to limit
+    // the cases where there are differences. The polymer-build issues an error
+    // when using packages/ inside lib without properly stepping out all the way
+    // to the packages folder. If users don't create symlinks in the source
+    // tree, then Dartium will also complain because it won't find the file seen
+    // in an HTML import.
+    var packagePath = uri.path.substring(
+        uri.path.lastIndexOf('packages/') + 'packages/'.length);
+    return new _ScriptInfo('$uri', packageUrl: 'package:$packagePath');
+  }
+
+  return new _ScriptInfo(baseUri, text: script.text);
+}
+
+/// Whether [uri] is an http URI that contains a 'packages' segment, and
+/// therefore could be converted into a 'package:' URI.
+bool _isHttpStylePackageUrl(Uri uri) {
+  var uriPath = uri.path;
+  return uri.scheme == _rootUri.scheme &&
+      // Don't process cross-domain uris.
+      uri.authority == _rootUri.authority &&
+      uriPath.endsWith('.dart') &&
+      (uriPath.contains('/packages/') || uriPath.startsWith('packages/'));
+}
+
+Iterable<String> discoverLibrariesToLoad(Document doc, String baseUri) =>
+    _discoverScripts(doc, baseUri).map(
+        (info) => _packageUrlExists(info) ? info.packageUrl : info.resolvedUrl);
+
+bool _packageUrlExists(_ScriptInfo info) =>
+    info.isPackage && _libs[Uri.parse(info.packageUrl)] != null;
+
+/// All libraries in the current isolate.
+final _libs = currentMirrorSystem().libraries;
+
+final Logger _loaderLog = new Logger('polymer.src.mirror_loader');
+
+/// Reads the library at [uriString] (which can be an absolute URI or a relative
+/// URI from the root library), and:
+///
+///   * If present, invokes any top-level and static functions marked
+///     with the [initMethod] annotation (in the order they appear).
+///
+///   * Registers any [PolymerElement] that is marked with the [CustomTag]
+///     annotation.
+void _loadLibrary(String uriString, List<Function> initializers) {
+  var uri = Uri.parse(uriString);
+  var lib = _libs[uri];
+
+  if (lib == null) {
+    _loaderLog.info('$uri library not found');
+    return;
+  }
+
+  // Search top-level functions marked with @initMethod
+  for (var f in lib.declarations.values.where((d) => d is MethodMirror)) {
+    _addInitMethod(lib, f, initializers);
+  }
+
+
+  // Dart note: we don't get back @CustomTags in a reliable order from mirrors,
+  // at least on Dart VM. So we need to sort them so base classes are registered
+  // first, which ensures that document.register will work correctly for a
+  // set of types within in the same library.
+  var customTags = new LinkedHashMap<Type, Function>();
+  for (var c in lib.declarations.values.where((d) => d is ClassMirror)) {
+    _loadCustomTags(lib, c, customTags);
+    // TODO(sigmund): check also static methods marked with @initMethod.
+    // This is blocked on two bugs:
+    //  - dartbug.com/12133 (static methods are incorrectly listed as top-level
+    //    in dart2js, so they end up being called twice)
+    //  - dartbug.com/12134 (sometimes "method.metadata" throws an exception,
+    //    we could wrap and hide those exceptions, but it's not ideal).
+  }
+
+  initializers.addAll(customTags.values);
+}
+
+void _loadCustomTags(LibraryMirror lib, ClassMirror cls,
+    LinkedHashMap registerFns) {
+  if (cls == null) return;
+  if (cls.hasReflectedType && cls.reflectedType == HtmlElement) return;
+
+  // Register superclass first.
+  _loadCustomTags(lib, cls.superclass, registerFns);
+
+  if (cls.owner != lib) {
+    // Don't register classes from different libraries.
+    // TODO(jmesserly): @CustomTag does not currently respect re-export, because
+    // LibraryMirror.declarations doesn't include these.
+    return;
+  }
+
+  var meta = _getCustomTagMetadata(cls);
+  if (meta == null) return;
+
+  if (!cls.hasReflectedType) {
+    var name = MirrorSystem.getName(cls.simpleName);
+    new Completer().completeError(new UnsupportedError('Custom element classes '
+        'cannot have type-parameters: $name'));
+    return;
+  }
+
+  registerFns.putIfAbsent(cls.reflectedType, () =>
+      () => Polymer.register(meta.tagName, cls.reflectedType));
+}
+
+/// Search for @CustomTag on a classemirror
+CustomTag _getCustomTagMetadata(ClassMirror c) {
+  for (var m in c.metadata) {
+    var meta = m.reflectee;
+    if (meta is CustomTag) return meta;
+  }
+  return null;
+}
+
+void _addInitMethod(ObjectMirror obj, MethodMirror method,
+    List<Function> initializers) {
+  var annotationFound = false;
+  for (var meta in method.metadata) {
+    if (identical(meta.reflectee, initMethod)) {
+      annotationFound = true;
+      break;
+    }
+  }
+  if (!annotationFound) return;
+  if (!method.isStatic) {
+    print("warning: methods marked with @initMethod should be static,"
+        " ${method.simpleName} is not.");
+    return;
+  }
+  if (!method.parameters.where((p) => !p.isOptional).isEmpty) {
+    print("warning: methods marked with @initMethod should take no "
+        "arguments, ${method.simpleName} expects some.");
+    return;
+  }
+  initializers.add(() => obj.invoke(method.simpleName, const []));
+}