Add a CanonicalizedMap class to pkg/collection.

pkg/collection/test/canonicalized_map_test.dart

Index: pkg/collection/test/canonicalized_map_test.dart
diff --git a/pkg/collection/test/canonicalized_map_test.dart b/pkg/collection/test/canonicalized_map_test.dart
new file mode 100644
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+++ b/pkg/collection/test/canonicalized_map_test.dart
@@ -0,0 +1,97 @@
+// 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.
+
+import "package:collection/collection.dart";
+import "package:unittest/unittest.dart";
+
+void main() {
+  group("with an empty canonicalized map", () {
+    var map;
+    setUp(() => map = new CanonicalizedMap((key) => key.toLowerCase()));
+
+    test("canonicalizes keys on set and get", () {
+      map["FoO"] = "value";
+      expect(map["fOo"], equals("value"));
+    });
+
+    test("canonicalizes keys for addAll", () {
+      map.addAll({
+        "FoO": "value 1",
+        "bAr": "value 2",
+        "baZ": "value 3"
+      });
+      expect(map["fOo"], equals("value 1"));
+      expect(map["BaR"], equals("value 2"));
+      expect(map["BAz"], equals("value 3"));
+    });
+
+    test("uses the final value for addAll collisions", () {
+      map.addAll({
+        "FoO": "value 1",
+        "foo": "value 2",
+        "FOO": "value 3"
+      });
+      expect(map.length, equals(1));
+      expect(map["fOo"], equals("value 3"));
+    });
+
+    test("canonicalizes keys for containsKey", () {
+      map["FoO"] = "value";
+      expect(map.containsKey("fOo"), isTrue);
+      expect(map.containsKey("bar"), isFalse);
+    });
+
+    test("canonicalizes keys for putIfAbsent", () {
+      map["FoO"] = "value";
+      expect(map.putIfAbsent("fOo", () => throw "shouldn't run"),
+          equals("value"));
+      expect(map.putIfAbsent("baR", () => "new value"), equals("new value"));
+    });
+
+    test("canonicalizes keys for remove", () {
+      map["FoO"] = "value";
+      expect(map.remove("bAr"), isNull);
+      expect(map.remove("fOo"), equals("value"));
+      expect(map, isEmpty);
+    });
+
+    test("uses original keys for keys", () {
+      map["FoO"] = "value 1";
+      map["bAr"] = "value 2";
+      expect(map.keys, equals(["FoO", "bAr"]));
+    });
+
+    test("uses original keys for forEach", () {
+      map["FoO"] = "value 1";
+      map["bAr"] = "value 2";
+
+      var keys = [];
+      map.forEach((key, value) => keys.add(key));
+      expect(keys, equals(["FoO", "bAr"]));
+    });
+  });
+
+  group("CanonicalizedMap.from", () {
+    test("canonicalizes its keys", () {
+      var map = new CanonicalizedMap.from({
+        "FoO": "value 1",
+        "bAr": "value 2",
+        "baZ": "value 3"
+      }, (key) => key.toLowerCase());
+      expect(map["fOo"], equals("value 1"));
+      expect(map["BaR"], equals("value 2"));
+      expect(map["BAz"], equals("value 3"));
+    });
+
+    test("uses the final value for collisions", () {
+      var map = new CanonicalizedMap.from({
+        "FoO": "value 1",
+        "foo": "value 2",
+        "FOO": "value 3"
+      }, (key) => key.toLowerCase());
+      expect(map.length, equals(1));
+      expect(map["fOo"], equals("value 3"));
+    });
+  });
+}