sinon.stub().withArgs() matches too often

[tbiesemann]

Sinon 6.1.5
This test fails:

it('sinon use constructor name when checking deepEquality', function() {
    class ClassWithoutProps {};
    const arg1 = new ClassWithoutProps(); //arg1.constructor.name === ClassWithoutProps
    const arg2 = new Proxy({}, {});	//arg2.constructor.name === Object
    const stub = sinon.stub();
    stub.withArgs(arg1).returns(5);
    const result = stub(arg2);
    assert.strictEqual(result, undefined); //[ERR_ASSERTION]: 5 === undefined
});

Describe the bug
withArgs() has too many matches.
Empty objects, instances of empty classes or proxies are all treated the same.
The deepEqual function in sinon returns true when comparing those.

One could use the constructor.name for further comparison in deepEqual, to solve some of these false matches.

[mgred]

@tbiesemann, @mroderick
Just found out that the samsam.deepEqual() is the function in charge here that returns true.
I opened an issue in the samsam repo sinonjs/samsam#37

[mroderick]

@mgred I don't think we're quite done yet

• npm install @sinonjs/samsam@2.1.0
• Adding a slightly modified version if the provided test to issues-test.js

describe("#1882", function () {
    it("should use constructor name when checking deepEquality", function () {
        class ClassWithoutProps {};
        const arg1 = new ClassWithoutProps(); //arg1.constructor.name === ClassWithoutProps
        const arg2 = new Proxy({}, {}); //arg2.constructor.name === Object
        const stub = sinon.stub();
        stub.withArgs(arg1).returns(5);
        const result = stub(arg2);
        assert.same(result, undefined); //[ERR_ASSERTION]: 5 === undefined
    });
});

Produces AssertionError: [assert.same] 5 expected to be the same object as undefined.

Would you take another look at this one?

[mgred]

@mroderick Sure I will.

Also: sinonjs/samsam#39

[mgred]

@mroderick, In the #1905 I added your test and it passes for me.

[mroderick]

@tbiesemann can you verify that the issue has been fixed in latest version of Sinon?

[fatso83]

This is failing on Internet Explorer 11. Two different runs:

• https://travis-ci.org/sinonjs/sinon/jobs/432356194
• https://travis-ci.org/sinonjs/sinon/jobs/432356194

[tbiesemann]

@mroderick Confirmed - Fix works with Sinon 6.3.4