Fix apollo-utilities isEqual bug due to missing hasOwnProperty check. (…

…#4072)
apollographql · Oct 29, 2018 · 4ef4633 · 4ef4633
1 parent 42dd7f8
commit 4ef4633
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git a/packages/apollo-utilities/src/util/__tests__/isEqual.ts b/packages/apollo-utilities/src/util/__tests__/isEqual.ts
@@ -83,4 +83,11 @@ describe('isEqual', () => {
     );
     expect(!isEqual(objNoProto, null)).toBe(true);
   });
+
+  it('should correctly handle modified prototypes', () => {
+    Array.prototype.foo = null;
+    expect(isEqual([1, 2, 3], [1, 2, 3])).toBe(true);
+    expect(!isEqual([1, 2, 3], [1, 2, 4])).toBe(true);
+    delete Array.prototype.foo;
+  });
 });
diff --git a/packages/apollo-utilities/src/util/isEqual.ts b/packages/apollo-utilities/src/util/isEqual.ts
@@ -32,7 +32,10 @@ export function isEqual(a: any, b: any): boolean {
     }
     // Look through all the keys in `b`. If `b` has a key that `a` does not, return false.
     for (const key in b) {
-      if (!Object.prototype.hasOwnProperty.call(a, key)) {
+      if (
+        Object.prototype.hasOwnProperty.call(b, key) &&
+        !Object.prototype.hasOwnProperty.call(a, key)
+      ) {
         return false;
       }
     }