From 950997e7348bf85a3a07b6f1a6a92dd8cd324d15 Mon Sep 17 00:00:00 2001
From: Mark Pedrotti <pedrottimark@gmail.com>
Date: Mon, 24 Dec 2018 07:45:24 -0500
Subject: [PATCH] expect: Test more precisely for class instance getters
 (#7477)

---
 CHANGELOG.md                                |  1 +
 packages/expect/src/__tests__/utils.test.js | 40 +++++++++++++++++++++
 packages/expect/src/utils.js                | 33 ++++++++++++-----
 3 files changed, 65 insertions(+), 9 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index dd9c3f7dd2c5..602f57bd5183 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -90,6 +90,7 @@
 - `[jest-haste-map]` Remove legacy condition for duplicate module detection ([#7333](https://github.com/facebook/jest/pull/7333))
 - `[jest-haste-map]` Fix `require` detection with trailing commas and ignore `import typeof` modules ([#7385](https://github.com/facebook/jest/pull/7385))
 - `[jest-cli]` Fix to set prettierPath via config file ([#7412](https://github.com/facebook/jest/pull/7412))
+- `[expect]` Test more precisely for class instance getters ([#7477](https://github.com/facebook/jest/pull/7477))
 - `[jest-cli]` Support dashed args ([#7497](https://github.com/facebook/jest/pull/7497))
 - `[jest-cli]` Fix to run in band tests if watch mode enable when runInBand arg used ([#7518](https://github.com/facebook/jest/pull/7518))
 - `[jest-runtime]` Fix mistake as test files when run coverage issue. ([#7506](https://github.com/facebook/jest/pull/7506))
diff --git a/packages/expect/src/__tests__/utils.test.js b/packages/expect/src/__tests__/utils.test.js
index 6a5e7d909680..43df140f68a7 100644
--- a/packages/expect/src/__tests__/utils.test.js
+++ b/packages/expect/src/__tests__/utils.test.js
@@ -13,6 +13,7 @@ const {
   emptyObject,
   getObjectSubset,
   getPath,
+  hasOwnProperty,
   subsetEquality,
 } = require('../utils');
 
@@ -94,6 +95,45 @@ describe('getPath()', () => {
   });
 });
 
+describe('hasOwnProperty', () => {
+  it('does inherit getter from class', () => {
+    class MyClass {
+      get key() {
+        return 'value';
+      }
+    }
+    expect(hasOwnProperty(new MyClass(), 'key')).toBe(true);
+  });
+
+  it('does not inherit setter from class', () => {
+    class MyClass {
+      set key(value) {}
+    }
+    expect(hasOwnProperty(new MyClass(), 'key')).toBe(false);
+  });
+
+  it('does not inherit method from class', () => {
+    class MyClass {
+      key() {}
+    }
+    expect(hasOwnProperty(new MyClass(), 'key')).toBe(false);
+  });
+
+  it('does not inherit property from constructor prototype', () => {
+    function MyClass() {}
+    MyClass.prototype.key = 'value';
+    expect(hasOwnProperty(new MyClass(), 'key')).toBe(false);
+  });
+
+  it('does not inherit __proto__ getter from Object', () => {
+    expect(hasOwnProperty({}, '__proto__')).toBe(false);
+  });
+
+  it('does not inherit toString method from Object', () => {
+    expect(hasOwnProperty({}, 'toString')).toBe(false);
+  });
+});
+
 describe('getObjectSubset()', () => {
   [
     [{a: 'b', c: 'd'}, {a: 'd'}, {a: 'b'}],
diff --git a/packages/expect/src/utils.js b/packages/expect/src/utils.js
index 24197cc2c50f..a3038e0abd80 100644
--- a/packages/expect/src/utils.js
+++ b/packages/expect/src/utils.js
@@ -21,18 +21,33 @@ type GetPath = {
   value?: any,
 };
 
-export const hasOwnProperty = (object: Object, value: string) => {
-  // Account for objects created using unconventional means such as
-  // `Object.create(null)`, in which case the `object.constructor` is undefined
-  // See: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create#Custom_and_Null_objects
-  const objectConstructor = object.constructor || Object;
-
-  return (
-    Object.prototype.hasOwnProperty.call(object, value) ||
-    Object.prototype.hasOwnProperty.call(objectConstructor.prototype, value)
+// Return whether object instance inherits getter from its class.
+const hasGetterFromConstructor = (object: Object, key: string) => {
+  const constructor = object.constructor;
+  if (constructor === Object) {
+    // A literal object has Object as constructor.
+    // Therefore, it cannot inherit application-specific getters.
+    // Furthermore, Object has __proto__ getter which is not relevant.
+    // Array, Boolean, Number, String constructors don’t have any getters.
+    return false;
+  }
+  if (typeof constructor !== 'function') {
+    // Object.create(null) constructs object with no constructor nor prototype.
+    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/create#Custom_and_Null_objects
+    return false;
+  }
+
+  const descriptor = Object.getOwnPropertyDescriptor(
+    constructor.prototype,
+    key,
   );
+  return descriptor !== undefined && typeof descriptor.get === 'function';
 };
 
+export const hasOwnProperty = (object: Object, key: string) =>
+  Object.prototype.hasOwnProperty.call(object, key) ||
+  hasGetterFromConstructor(object, key);
+
 export const getPath = (
   object: Object,
   propertyPath: string | Array<string>,