Expose the content of Maps and WeakMaps through MapMirror.

test/mjsunit/harmony/mirror-collections.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --expose-debug-as debug --expose-gc --harmony-collections
+
+function testMapMirror(mirror) {
+    // Create JSON representation.
+    var serializer = debug.MakeMirrorSerializer();

[Yang, 2014/07/16 12:10:58]

Same here. 2 space indentation please.

[Alexandra Mikhaylova, 2014/07/16 17:00:37]

Done.

+    var json = JSON.stringify(serializer.serializeValue(mirror));
+
+    // Check the mirror hierachy.
+    assertTrue(mirror instanceof debug.Mirror);
+    assertTrue(mirror instanceof debug.ValueMirror);
+    assertTrue(mirror instanceof debug.ObjectMirror);
+    assertTrue(mirror instanceof debug.MapMirror);
+
+    assertTrue(mirror.isMap());
+
+    // Parse JSON representation and check.
+    var fromJSON = eval('(' + json + ')');
+    assertEquals('map', fromJSON.type);
+}
+
+var o1 = new Object();
+var o2 = new Object();
+var o3 = new Object();
+
+// Test the mirror object for Maps
+var map = new Map();
+map.set(o1, 11);
+map.set(o2, 22);
+map.delete(o1);
+var mapMirror = debug.MakeMirror(map);
+testMapMirror(mapMirror);
+var entries = mapMirror.entries();
+assertEquals(2, entries.length);
+assertSame(o2, entries[0]);
+assertEquals(22, entries[1]);
+map.set(o1, 33);
+map.set(o3, o2);
+map.delete(o2);
+map.set(undefined, 44);
+entries = mapMirror.entries();
+assertEquals(6, entries.length);
+assertSame(o1, entries[0]);
+assertEquals(33, entries[1]);
+assertSame(o3, entries[2]);
+assertSame(o2, entries[3]);
+assertEquals(undefined, entries[4]);
+assertEquals(44, entries[5]);

[Yang, 2014/07/16 12:10:58]

Having MapMirror.entries() contain both keys and value is somewhat confusing. It
would be nicer to have an array of key/value pairs. That way, entries.length
will also not be twice the actual number of added mappings.

On the other hand that would add some more overhead when preparing that array.

We could have methods on MapMirror that would abstract away from direct access
to entries, but then it becomes unclear when to refresh the entries array.

:/

[Alexandra Mikhaylova, 2014/07/16 17:00:37]

I've changed the return value of MapMirror.entries() to the array of key/value
pairs (objects).

I don't quite get the second part of your comment, however. We'd just like to be
able to pull all entries from a map at the given moment. So, it's kind of a
snapshot of the map. Could there be any issues with it?

+
+// Test the mirror object for WeakMaps
+var weakMap = new WeakMap();
+weakMap.set(o1, 11);
+weakMap.set(new Object(), 22);
+weakMap.set(o3, 33);
+var weakMapMirror = debug.MakeMirror(weakMap);
+testMapMirror(weakMapMirror);
+
+function testWeakMapMirrorBeforeGC(mirror) {
+    var entries = mirror.entries();
+    assertEquals(6, entries.length);
+    assertEquals(11, entries[entries.indexOf(o1) + 1]);
+    assertEquals(33, entries[entries.indexOf(o3) + 1]);
+    assertTrue(entries.indexOf(22) >= 1);
+}
+
+testWeakMapMirrorBeforeGC(weakMapMirror);
+gc();
+
+function testWeakMapMirrorAfterGC(mirror) {
+    var entries = mirror.entries();
+    assertEquals(4, entries.length);
+    assertEquals(11, entries[entries.indexOf(o1) + 1]);
+    assertEquals(33, entries[entries.indexOf(o3) + 1]);
+    assertTrue(entries.indexOf(22) == -1);
+}
+
+testWeakMapMirrorAfterGC(weakMapMirror);