[react-packager][streamline oss] Move open sourced JS source to react-native-github

Libraries/Utilities/deepFreezeAndThrowOnMutationInDev.js

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+/**
+ * Copyright 2004-present Facebook. All Rights Reserved.
+ *
+ * @providesModule deepFreezeAndThrowOnMutationInDev
+ */
+
+/**
+ * If your application is accepting different values for the same field over
+ * time and is doing a diff on them, you can either (1) create a copy or
+ * (2) ensure that those values are not mutated behind two passes.
+ * This function helps you with (2) by freezing the object and throwing if
+ * the user subsequently modifies the value.
+ *
+ * There are two caveats with this function:
+ *   - If the call site is not in strict mode, it will only throw when
+ *     mutating existing fields, adding a new one
+ *     will unfortunately fail silently :(
+ *   - If the object is already frozen or sealed, it will not continue the
+ *     deep traversal and will leave leaf nodes unfrozen.
+ *
+ * Freezing the object and adding the throw mechanism is expensive and will
+ * only be used in DEV.
+ */
+function deepFreezeAndThrowOnMutationInDev(object) {
+  if (__DEV__) {
+    if (typeof object !== 'object' ||
+        object === null ||
+        Object.isFrozen(object) ||
+        Object.isSealed(object)) {
+      return;
+    }
+
+    for (var key in object) {
+      if (object.hasOwnProperty(key)) {
+        object.__defineGetter__(key, identity.bind(null, object[key]));
+        object.__defineSetter__(key, throwOnImmutableMutation.bind(null, key));
+        deepFreezeAndThrowOnMutationInDev(object[key]);
+      }
+    }
+    Object.freeze(object);
+    Object.seal(object);
+  }
+}
+
+function throwOnImmutableMutation(key, value) {
+  throw Error(
+    'You attempted to set the key `' + key + '` with the value `' +
+    JSON.stringify(value) + '` on an object that is meant to be immutable ' +
+    'and has been frozen.'
+  );
+}
+
+function identity(value) {
+  return value;
+}
+
+module.exports = deepFreezeAndThrowOnMutationInDev;