Skeleton API for lazy library loading.

dart/sdk/lib/async/deferred_load.dart

Index: dart/sdk/lib/async/deferred_load.dart
diff --git a/dart/sdk/lib/async/deferred_load.dart b/dart/sdk/lib/async/deferred_load.dart
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+// Copyright (c) 2013, 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.
+
+/**
+ * Indicates that loading of [libraryName] is deferred.
+ *
+ * Applies to library imports, when used as metadata.
+ *
+ * Example usage:
+ *
+ * [:
+ * @lazy

[kasperl, 2013/02/18 13:53:08]

So lazy is a user-chosen name now. Neat. Maybe we should come naming guidelines?
You import with the prefix 'foo' so you call the deferred library instance
deferred$foo? deferredFoo?

[ahe, 2013/02/18 14:32:11]

I would use "lazyFoo", but I'll let other people have fun with guidelines. I
don't expect we'll see any in the Dart SDK.

+ * import 'foo.dart' as foo;
+ *
+ * const lazy = const DeferredLibrary('com.example.foo');
+ *
+ * void main() {
+ *   foo.method(); // Throws a NoSuchMethodError, foo is not loaded yet.
+ *   lazy.load().then(onFooLoaded);
+ * }
+ *
+ * void onFooLoaded(_) {
+ *   foo.method();
+ * }
+ * :]
+ */
+class DeferredLibrary {
+  final String libraryName;
+  final String uri;
+
+  const DeferLoad(this.libraryName, {this.uri});

[kasperl, 2013/02/18 13:53:08]

DeferredLibrary

[ahe, 2013/02/18 14:32:11]

Done.

+
+  /**
+   * Ensure that [libraryName] has been loaded.
+   *
+   * The value of the returned future is true if this invocation of
+   * [load] caused the library to be loaded.
+   */
+  external Future<bool> load();
+}