Introduce LibraryUpdater.

dart/tests/try/poi/library_updater_test.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.
+
+// Test of LibraryUpdater.
+library trydart.library_updater_test;
+
+import 'dart:convert' show
+    UTF8;
+
+import 'package:dart2js_incremental/library_updater.dart' show
+    LibraryUpdater,
+    Update;
+
+import 'package:compiler/implementation/elements/elements.dart' show
+    LibraryElement;
+
+import 'compiler_test_case.dart';
+
+void nolog(_) {}
+
+class LibraryUpdaterTestCase extends CompilerTestCase {
+  final String newSource;
+
+  final bool expectedCanReuse;
+
+  final List<String> expectedUpdates;
+
+  LibraryUpdaterTestCase(
+      String source,
+      this.newSource,
+      this.expectedCanReuse,

[Johnni Winther, 2014/09/29 09:37:57]

Change these to named arguments.

[ahe, 2014/09/29 11:44:42]

I really wish we had mandatory named arguments. I think my trade-off is
different from yours--I prefer to be sure that the exact number of arguments
have been passed--but in the interest of making the tests more readable, I've
changed to named arguments.

+      this.expectedUpdates)
+      : super(source);
+
+  Future run() => mainApp.then((LibraryElement library) {
+    LibraryUpdater updater =
+        new LibraryUpdater(this.compiler, null, scriptUri, nolog, nolog);
+    bool actualCanReuse =
+        updater.canReuseLibrary(library, UTF8.encode(newSource));
+    Expect.equals(expectedCanReuse, actualCanReuse);
+
+    Expect.setEquals(
+        expectedUpdates.toSet(),
+        updater.updates.map((Update update) => update.before.name).toSet());
+  });
+
+  String toString() => 'Before:\n$source\n\n\nAfter:\n$newSource';
+}
+
+void main() {
+  runTests(
+      [
+          // Only method body changed. Can be reused if 'main' is
+          // updated/patched.
+          new LibraryUpdaterTestCase(
+              'main() { print("Hello, World!"); }',
+              'main() { print("Hello, Brave New World!"); }',
+              true,
+              ['main']),
+
+          // Signature changed. Can't be reused.
+          new LibraryUpdaterTestCase(
+              'main() { print("Hello, World!"); }',
+              'void main() { print("Hello, World!"); }',
+              false,
+              []),
+
+          // Only whitespace changes. Can be reused; no updates/patches needed.

[Johnni Winther, 2014/09/29 09:34:42]

Add a test for whitespace in the signature.

[ahe, 2014/09/29 11:44:42]

Done.

+          new LibraryUpdaterTestCase(
+              'main(){print("Hello, World!");}',
+              'main() { print ( "Hello, World!" ) ; }',
+              true,
+              []),
+
+
+          // Arrow function changed to method body. Can be reused if 'main' is
+          // updated/patched.
+          new LibraryUpdaterTestCase(
+              'main() => null',
+              'main() { return null; }',
+              true,
+              ['main']),
+
+          // Empty body changed to contain a statement. Can be reused if 'main'
+          // is updated/patched.
+          new LibraryUpdaterTestCase(
+              'main() {}',
+              'main() { return null; }',
+              true,
+              ['main']),
+
+          // Empty body changed to arrow. Can be reused if 'main'
+          // is updated/patched.
+          new LibraryUpdaterTestCase(
+              'main() {}',
+              'main() => null;',
+              true,
+              ['main']),
+
+          // Arrow changed to empty body. Can be reused if 'main'
+          // is updated/patched.
+          new LibraryUpdaterTestCase(
+              'main() => null;',
+              'main() {}',
+              true,
+              ['main']),
+
+          // TODO(ahe): When supporting class members, test abstract methods.
+      ]
+  );
+}