Use browsers JSON.parse for parsing JSON.

sdk/lib/_internal/compiler/implementation/lib/json_patch.dart

Index: sdk/lib/_internal/compiler/implementation/lib/json_patch.dart
diff --git a/sdk/lib/_internal/compiler/implementation/lib/json_patch.dart b/sdk/lib/_internal/compiler/implementation/lib/json_patch.dart
new file mode 100644
index 0000000000000000000000000000000000000000..14642bf4ccbb554ac0af78c1fbe8554bd9d83697
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+++ b/sdk/lib/_internal/compiler/implementation/lib/json_patch.dart
@@ -0,0 +1,66 @@
+// Patch file for dart:json library.

[Lasse Reichstein Nielsen, 2013/01/31 06:58:44]

Needs copyright header.

[sra1, 2013/01/31 22:49:36]

Done.

+
+import 'dart:_foreign_helper' show JS;
+
+part of dart.json;

[Lasse Reichstein Nielsen, 2013/01/31 06:58:44]

Does this parse? You usually can't have "part of" in the same file as an
"import". Maybe it's just ignored for patch-files, but it still looks odd.

[Johnni Winther, 2013/01/31 08:32:59]

Yes, it looks odd. It should be removed.

[sra1, 2013/01/31 22:49:36]

Done.

+
+/**
+ * Parses [json] and build the corresponding parsed JSON value.
+ *
+ * Parsed JSON values are of the types [num], [String], [bool], [Null],
+ * [List]s of parsed JSON values or [Map]s from [String] to parsed
+ * JSON values.
+ *
+ * The optional [revivier] function, if provided, is called once for each object

[Johnni Winther, 2013/01/31 08:32:59]

revivier -> reviver

[sra1, 2013/01/31 22:49:36]

Done.

+ * or list property parsed. The arguments are the property name ([String]) or
+ * list index ([int]), and the value is the parsed value.  The return value of
+ * the revivier will be used as the value of that property instead the parsed

[Johnni Winther, 2013/01/31 08:32:59]

ditto

[sra1, 2013/01/31 22:49:36]

Done.

+ * value.  The top level value is passed to the reviver with the empty string as
+ * a key.
+ *
+ * Throws [FormatException] if the input is not valid JSON text.
+ */
+patch parse(String json, [reviver(var key, var value)]) {

[Lasse Reichstein Nielsen, 2013/01/31 06:58:44]

You can't patch a function that isn't marked external.
(Or, if you can, it's a bug, so please report it and stop doing it :).
I.e., you must mark the method external in the JSON library and move the
original implementation to the VM's patch file.

[Johnni Winther, 2013/01/31 08:32:59]

There is a pending CL that enforces this.

[sra1, 2013/01/31 22:49:36]

Which CL is that?
Please don't commit until I have solved the my current problem.

Adding 'external' requires I have a patch in the VM too.

I'm blocked on the VM side, and seeking help from the VM team.
At this point it looks like a simple change like this requires writing C++ code
and changing multiple VM files. We should improve the 'patch' feature to be more
usable if that is true.

[Johnni Winther, 2013/02/01 06:20:10]

The CL is https://codereview.chromium.org/11864010/. I'll hold it back until you
commit. 'external' is currently only enforced on members but not on top level
functions. The CL is meant to fix that.

+  if (json is! String) throw new ArgumentError(json);
+
+  var parsed;
+  try {
+    parsed = JS('=Object|=List|Null|bool|num|String', 'JSON.parse(#)', json);
+  } catch (e) {
+    throw new FormatException(JS('String', 'String(#)', e));
+  }
+
+  return _convertJsonToDart(parsed, reviver);
+}
+
+/**
+ * Walks the [json] value, replacing JavaScript Objects with Maps.
+ */
+_convertJsonToDart(json, reviver(key, value)) {
+
+  var revive = reviver == null ? (key, value) => value : reviver;
+
+  walk(e) {

[Lasse Reichstein Nielsen, 2013/01/31 06:58:44]

Here "e" is really a JS object, not a Dart object, so maybe allow yourself to
do:
  if (e === null || !JS("bool", 'typeof # == "object"', e)) {
    return e;
  }

[sra1, 2013/01/31 22:49:36]

Done.

+    if (e is String) return e;
+    if (e is num) return e;
+    if (e is bool) return e;
+    if (e == null) return e;
+    if (e is List) {
+      // In-place update of the elements since JS Array is a Dart List.
+      for (int i = 0; i < e.length; i++) {
+        e[i] = revive(i, walk(e[i]));
+      }
+      return e;
+    }
+    // Else it is a plain Object, copy to a Map.
+    var keys = JS('=List', 'Object.keys(#)', e);

[Lasse Reichstein Nielsen, 2013/01/31 06:58:44]

Notice that V8 still has a bug handling keys named "__proto__"
(<https://code.google.com/p/v8/issues/detail?id=621>, +mstarzinger).
That means that '{"__proto__": {"x": 42}, "y": 37}' collapses to '{"x":42,
"y":37}' using the JS parse, but worked with the Dart one.

Probably not something that happens in practice, though.

[sra1, 2013/01/31 22:49:36]

Interesting.
Object.keys(o) for this example returns ["y"]
So this code will completely drop the __proto__, giving a third behavior.  I'll
add a comment about the issue in case it becomes something in practice.

+    var map = {};
+    for (int i = 0; i < keys.length; i++) {
+      String key = keys[i];
+      map[key] = revive(key, walk(JS('', '#[#]', e, key)));
+    }
+    return map;
+  }
+
+  return revive('', walk(json));
+}