Do not freeze array buffer views

Reviewed By: alunyov

Differential Revision: D49106461

fbshipit-source-id: c5046677b93283601482f4bfaea3723776658129

packages/relay-runtime/util/__tests__/deepFreeze-test.js

@@ -53,4 +53,10 @@ describe('deepFreeze()', () => {
   it('copes with null values', () => {
     expect(deepFreeze({a: null})).toBeFrozen();
   });
+
+  it('does not throw on array buffers', () => {
+    const x = new Uint16Array([21, 31]);
+    expect(() => deepFreeze(x)).not.toThrow();
+    expect(() => deepFreeze({x})).not.toThrow();
+  });
 });

packages/relay-runtime/util/deepFreeze.js

@@ -18,6 +18,9 @@
  * returns the now-frozen original object.
  */
 function deepFreeze<T: {...}>(object: T): T {
+  if (!shouldBeFrozen(object)) {
+    return object;
+  }
   Object.freeze(object);
   Object.getOwnPropertyNames(object).forEach(name => {
     const property = object[name];
@@ -32,4 +35,18 @@ function deepFreeze<T: {...}>(object: T): T {
   return object;
 }
 
+function shouldBeFrozen(value: mixed): boolean {
+  // Primitives and functions:
+  if (value === null || typeof value !== 'object') {
+    return false;
+  }
+
+  // Views on array buffers cannot be frozen
+  if (ArrayBuffer.isView(value)) {
+    return false;
+  }
+
+  return true;
+}
+
 module.exports = deepFreeze;