toMatchObject seems to ignore Map and Set

[fabiosantoscode]

🐛 Bug Report

I've noticed that .toMatchObject ignores any Map and Set objects, silently accepting different things.

To Reproduce

Steps to reproduce the behavior:

Attempt to match an object against a Map or Set, for example:

expect({ hello: 'world' }).toMatchObject(new Set()); // Passes, should fail
expect({ hello: [] }).toMatchObject({ hello: new Map() }); // Passes, should fail

Expected behavior

The test should fail, because Map and Set are always different from strings and arrays.

Link to repl or repo (highly encouraged)

https://replit.com/@fabiosantoscode/jest-playground#matchobject.test.js

envinfo

  System:
    OS: Linux 5.8 Ubuntu 20.04.2 LTS (Focal Fossa)
    CPU: (8) x64 Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz
  Binaries:
    Node: 15.4.0 - ~/.nvm/versions/node/v15.4.0/bin/node
    Yarn: 1.22.10 - ~/.nvm/versions/node/v15.4.0/bin/yarn
    npm: 7.6.3 - ~/.nvm/versions/node/v15.4.0/bin/npm
  npmPackages:
    jest: 26.2.2 => 26.2.2 

(and also in the REPL, which has this envinfo)

  System:
    OS: Linux 5.4 Debian GNU/Linux 9 (stretch) 9 (stretch)
    CPU: (4) x64 Intel(R) Xeon(R) CPU @ 2.30GHz
  Binaries:
    Node: 12.21.0 - /usr/local/bin/node
    Yarn: 1.22.5 - /usr/local/bin/yarn
    npm: 6.14.11 - /usr/local/bin/npm
  npmPackages:
    jest: ^26.6.3 => 26.6.3 

[fabiosantoscode]

May be related to #11112 -- RegExp objects also have the same effect as Map in this case.

[julienw]

Just got into this as well. The fact that it silently accepts the value and passes the test is error-prone.

[fabiosantoscode]

Fixed the REPL to make it clearer. I started experimenting with regexes shortly after I posted this issue, but then I didn't revert my changes :)

[github-actions]

This issue is stale because it has been open for 1 year with no activity. Remove stale label or comment or this will be closed in 30 days.

[fabiosantoscode]

I've updated the reproduction REPL to use Jest 29.4.3, and can still reproduce this issue.

[szimek]

I've just ran into this issue when trying to use expect.objectContains with a value that is a Map.

This issue describes the problem: #13968, but is unfortunately already closed.