Jest: Snapshot property matchers mutate passed-in object

[SimenB]

🐛 Bug Report

When using property matchers in snapshots (https://jestjs.io/docs/en/snapshot-testing#property-matchers) the matcher mutates the object.

To Reproduce

test('some test', () => {
    const object = { foo: 'bar' };

    expect(typeof object.foo).toBe('string');

    expect(object).toMatchSnapshot({ foo: expect.any(String) });

    expect(typeof object.foo).toBe('string');
});

That test will fail the last assertion.

Expected behavior

The passed in object should not be mutated.

Link to repl or repo (highly encouraged)

REPL is on Jest 22, but see "To reproduce"

Run npx envinfo --preset jest

Paste the results here:

  System:
    OS: macOS Sierra 10.12.6
    CPU: x64 Intel(R) Core(TM) i7-4980HQ CPU @ 2.80GHz
  Binaries:
    Node: 8.11.1 - ~/.nvm/versions/node/v8.11.1/bin/node
    Yarn: 1.7.0 - /usr/local/bin/yarn
    npm: 6.1.0 - ~/.nvm/versions/node/v8.11.1/bin/npm
  npmPackages:
    jest: ^23.1.0 => 23.1.0

[SimenB]

Note that this _might_ be solved by #6528, but that might take some time to land, so opening up a separate issue.

Fix should be here: https://github.com/facebook/jest/blob/6c61baa76e366a9a7bfb351108a2d4ca97820bf9/packages/jest-snapshot/src/index.js#L147

(don't Object.assign into received)

[rickhanlonii]

Oops, duh

[rickhanlonii]

Yeah #6528 will solve this and has a test for it