163495 2016-10-15 17:15:19 -0700 JSON.parse should modify configurable non-writable properties. 2016-10-15 17:19:35 -0700 1 1 1 Unclassified WebKit JavaScriptCore WebKit Local Build Unspecified Unspecified ASSIGNED P2 Normal --- 163446 1 mark.lam mark.lam fpizlo ggaren jfbastien keith_miller msaboff saam ysuzuki oldest_to_newest 1240676 0 mark.lam 2016-10-15 17:15:19 -0700 This is because the JSON.parse spec (see https://tc39.github.io/ecma262/#sec-json.parse and https://tc39.github.io/ecma262/#sec-internalizejsonproperty) uses CreateDataProperty to set properties that the reviver wants to set. The CreateDataProperty spec (see https://tc39.github.io/ecma262/#sec-createdataproperty) says that it uses [[DefineOwnProperty]] to perform this set. As a result, if the property was configurable to begin with, it's [[Writable]] will be overridden to be true, and the new value should be applied. 1240677 1 mark.lam 2016-10-15 17:17:34 -0700 We can't do this currently achieve this for array like objects, because the existing code path that does the "put" operation does not allow us to indicate that the put with a DefineOwnProperty mode. 1240678 2 mark.lam 2016-10-15 17:19:35 -0700 A test case in JSTests/stress/json-parse-on-non-configurable-non-writable-property.js (which should land with https://bugs.webkit.org/show_bug.cgi?id=163446) is commented out due to this bug. Please uncomment that test when this is fixed.