toEqual throws a TypeError when using getter to private field of class #10167
Description
🐛 Bug Report
Jest throws a TypeError when using toEqual or toMatchObject in a class with private fields (those starting by #) and a getter that exposes the value. I guess other similar matchers like toStrictEqual also fails but didn't test. I tested this using jest-circus and fails the same way.
The class under test has a private field #foo and a getter get foo() that returns the value of #foo. Using toMatchObject with the name of the getter (something like .toMatchObject({ foo: 0 })) works when the value is equal but throws a TypeError when are distinct (I bet when trying to show the differences, but I haven't debugged).
To Reproduce
class X {
#foo = 42;
get foo() {
return this.#foo;
}
}
test("it works and test pass", () => {
const x = new X();
expect(x.foo).toEqual(42);
});
test("it also works and test pass", () => {
const x = new X();
expect(x).toMatchObject({ foo: 42 });
});
test("it works, the test fail since values are distinct", () => {
const x = new X();
expect(x.foo).toEqual(0);
// Expected: 0, Received: 42
});
test("it doesn't work, matcher throws a TypeError", () => {
const x = new X();
expect(x).toMatchObject({ foo: 0 });
// TypeError: Cannot read private member #foo from an object whose class did not declare it
});
test("also doesn't work, matcher throws a TypeError", () => {
const x = new X();
expect(x).toEqual({ foo: 0 });
// TypeError: Cannot read private member #foo from an object whose class did not declare it
});Expected behavior
Last two test fail properly since property foo are distinct between expected and received objects, showing the right report.
envinfo
System:
OS: Linux 5.6 Arch Linux
CPU: (8) x64 Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz
Binaries:
Node: 12.17.0 - /usr/bin/node
npm: 6.14.5 - /usr/bin/npm
npmPackages:
jest: ^26.0.1 => 26.0.1