Adds limited support for private classes.

test_reflectable/test/private_class_test.dart

+// Copyright (c) 2015, the Dart Team. All rights reserved. Use of this
+// source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+
+/// File being transformed by the reflectable transformer.
+/// Uses public features of an instance of a private class in a different
+/// library. This illustrates that there is (very limited) support for access
+/// to private features.
+library test_reflectable.test.private_class_test;
+
+@GlobalQuantifyCapability("PublicClass", privacyReflectable)
+import 'package:reflectable/reflectable.dart';
+import 'package:unittest/unittest.dart';
+import 'private_class_library.dart';
+
+class PrivacyReflectable extends Reflectable {
+  const PrivacyReflectable()
+      : super(
+            subtypeQuantifyCapability,
+            reflectedTypeCapability,
+            instanceInvokeCapability,
+            declarationsCapability,
+            libraryCapability);
+}
+
+const privacyReflectable = const PrivacyReflectable();
+
+void testPrivacyViolation(PublicClass object, String description) {
+  test("Privacy violation, $description", () {
+    Map<Uri, LibraryMirror> libraries = privacyReflectable.libraries;
+    Uri libraryUri = libraries.keys.firstWhere(
+        (Uri uri) => uri.toString().contains("private_class_library"));
+    LibraryMirror library = libraries[libraryUri];
+    expect(
+        library.declarations.keys,
+        <String>[
+          "PublicClass",
+          "_PrivateClass1",
+          "_PrivateClass2",
+          "PublicSubclass1",
+          "PublicSubclass2"
+        ].toSet());
+
+    InstanceMirror instanceMirror = privacyReflectable.reflect(object);

[sigurdm, 2015/10/15 12:30:58]

I think the right way to allow reflection on private sub-classes is to make
support for admitSubtypesCapability that uses is-checks (in some well-defined
order) to choose the classmirror to return.

[sigurdm, 2015/10/15 12:30:58]

What about other actions on private class-mirrors?

* invoking static functions
* invoking constructors

Without a backdoor the support for private access is necessarily very sketchy.
Maybe it is better to just warn up front (perhaps with logger.fine) and then
ignore the private classes.

[eernst, 2015/10/15 13:46:11]

For now, I've changed the test to check `canReflect` and see that it says
`false` on the private classes.

[eernst, 2015/10/15 13:46:11]

Now you won't get a mirror on them, so we can revisit that later when they
return.

+    ClassMirror classMirror = instanceMirror.type;
+    classMirror.declarations.values.forEach((DeclarationMirror declaration) {
+      expect(declaration is MethodMirror, true);
+      MethodMirror method =
+          declaration; // Declaration needed, no type propagation.
+      expect(method.reflectedReturnType, int);
+      expect(method.parameters.length, 0);
+      expect(
+          <String>["publicMethod", "supposedlyPrivate", "supposedlyPrivateToo"]
+              .contains(method.simpleName),
+          true);
+      if (method.simpleName != "publicMethod") {
+        expect(instanceMirror.invoke(declaration.simpleName, []),
+            -object.publicMethod());
+      }
+    });
+  });
+}
+
+main() {
+  testPrivacyViolation(func1(), "private subclass");
+  testPrivacyViolation(func2(), "private subtype");
+  testPrivacyViolation(func3(), "public subclass of private subclass");
+  testPrivacyViolation(func4(), "public subclass of private subtype");
+}