extend is not handling property descriptors with accessors

[marcospont]

The 'extend' function from 'util/core' is not handling property descriptors using accessors properly.

The issue was introduced by the following commit: f981192

The below test can be used to duplicate the issue. The object 'obj' has a 'pub' property that is defined using a getter and a setter. Once 'extend' is called, the property descriptor is recreated using 'value' and ignoring the accessors.

import extend from 'sinon/lib/sinon/util/core/extend';

describe('extend', () => {
	it('must preserve accessors', () => {
		const obj = {
			_priv: 1
		};

		Object.defineProperty(obj, 'pub', {
			configurable: true,
			get: () => obj._priv,
			set: value => {
				obj._priv = value;
			}
		});

		const newObj = {};

		extend(newObj, obj);

		expect(newObj['pub']).toBe(1);
	});
});

[fatso83]

Good find!

[sauravazad]

There is an inherent mistake in the implementation as it does not distinguishes between Data property and Accessor property

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#properties

• Data property
  Associates a key with a value, and has the following attributes:

Attributes of a data property

Attribute	Type	Description	Default value
[[Value]]	Any JavaScript type	The value retrieved by a get access of the property.	undefined
[[Writable]]	Boolean	If false, the property's [[Value]] cannot be changed.	false
[[Enumerable]]	Boolean	If true, the property will be enumerated in for...in loops.See also Enumerability and ownership of properties.	false
[[Configurable]]	Boolean	If false, the property cannot be deleted, cannot be changed to an accessor property, and attributes other than [[Value]] and [[Writable]] cannot be changed.	false

• Accessor property
  Associates a key with one of two accessor functions (get and set) to retrieve or store a value, and has the following attributes:

Attributes of an accessor property

Attribute	Type	Description	Default value
[[Get]]	Function object or undefined	The function is called with an empty argument list and retrieves the property value whenever a get access to the value is performed.See also get.	undefined
[[Set]]	Function object or undefined	The function is called with an argument that contains the assigned value and is executed whenever a specified property is attempted to be changed.See also set.	undefined
[[Enumerable]]	Boolean	If true, the property will be enumerated in for...in loops.	false
[[Configurable]]	Boolean	If false, the property can't be deleted and can't be changed to a data property.	false

I have raised a PR to fix the behavior #2391.

[mroderick]

This has been fixed by #2391 and published to the npm registry as sinon@11.1.2