[Feature]: Support array inputs to toMatchSnapshot() matcher

[bjoluc]

🚀 Feature Proposal

Currently,

expect([{}]).toMatchSnapshot([expect.anything()]);

fails with

expect(received).toMatchSnapshot(properties)

Matcher error: Expected properties must be an object

Expected properties has type:  array
Expected properties has value: [Anything]

(#13134, example repo here).

Motivation

This used to work in Jest v27 and would allow test cases like this again. It would help to avoid wrapping arrays in objects solely for the sake of snapshot testing.

Example

Something like

expect([{}, "foo"]).toMatchSnapshot([expect.anything(), "foo"]);

Pitch

This was supported in Jest v27 and the wording toMatchSnapshot feels very intuitive as opposed to some custom toMatchArraySnapshot (or the like) matcher. As a neat side effect, this would also allow to snapshot-test function parameter arrays.

[SimenB]

Happy to take a PR adding support for this. 👍

If it used to work in Jest 27, it should be possible to go back and bisect to see what broke it.

[JamieMagee]

I think this should be changed to a bug report instead of a feature request. This was working for us in jest v29.0.3, but is broken when attempting to upgrade to v29.1.2.

Here's a sample reproduction from our repo:

expect(
  getLockedDependencies(bundledPackageLockJson, 'ansi-regex', '3.0.0')
).toMatchSnapshot([
  {
    bundled: true,
    dev: true,
    integrity: 'sha1-7QMXwyIGT3lGbAKWa922Bas32Zg=',
    resolved:
      'https://registry.npmjs.org/ansi-regex/-/ansi-regex-3.0.0.tgz',
    version: '3.0.0',
  },
]);

which errors with

Error: expect(received).toMatchSnapshot(properties)

Matcher error: Expected properties must be an object

Expected properties has type:  array
Expected properties has value: [{"bundled": true, "dev": true, "integrity": "sha1-7QMXwyIGT3lGbAKWa922Bas32Zg=", "resolved": "https://registry.npmjs.org/ansi-regex/-/ansi-regex-3.0.0.tgz", "version": "3.0.0"}]

    at Object.toMatchSnapshot (C:\src\renovate\node_modules\jest-snapshot\build\index.js:246:13)
    at __EXTERNAL_MATCHER_TRAP__ (C:\src\renovate\node_modules\expect\build\index.js:346:30)
    at Object.throwingMatcher (C:\src\renovate\node_modules\expect\build\index.js:347:15)
    at Object.<anonymous> (C:\src\renovate\lib\modules\manager\npm\update\locked-dependency\package-lock\get-locked.spec.ts:52:9)
    at Promise.then.completed (C:\src\renovate\node_modules\jest-circus\build\utils.js:333:28)
    at new Promise (<anonymous>)
    at callAsyncCircusFn (C:\src\renovate\node_modules\jest-circus\build\utils.js:259:10)
    at _callCircusTest (C:\src\renovate\node_modules\jest-circus\build\run.js:277:40)
    at async _runTest (C:\src\renovate\node_modules\jest-circus\build\run.js:209:3)
    at async _runTestsForDescribeBlock (C:\src\renovate\node_modules\jest-circus\build\run.js:97:9)
    at async _runTestsForDescribeBlock (C:\src\renovate\node_modules\jest-circus\build\run.js:91:9)
    at async _runTestsForDescribeBlock (C:\src\renovate\node_modules\jest-circus\build\run.js:91:9)
    at async run (C:\src\renovate\node_modules\jest-circus\build\run.js:31:3)
    at async runAndTransformResultsToJestFormat (C:\src\renovate\node_modules\jest-circus\build\legacy-code-todo-rewrite\jestAdapterInit.js:136:21)
    at async jestAdapter (C:\src\renovate\node_modules\jest-circus\build\legacy-code-todo-rewrite\jestAdapter.js:92:19)
    at async runTestInternal (C:\src\renovate\node_modules\jest-runner\build\runTest.js:407:16)
    at async runTest (C:\src\renovate\node_modules\jest-runner\build\runTest.js:491:34)

[bjoluc]

@JamieMagee I previously opened #13134. Interestingly, my repro doesn't work with "jest": "29.0.3" neither 😕

[terencetcf]

A quick workaround is to wrap the array into an object. For example:

expect({ theArray }).toMatchSnapshot({ theArray: [...] });

[github-actions]

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

[rarkins]

Not stale

[bryanjtc]

Any update on this?

[bakasmarius]

Happy to take a PR adding support for this. 👍

If it used to work in Jest 27, it should be possible to go back and bisect to see what broke it.

I created a PR (#14025) that undoes the changes that broke the functionality.

[bakasmarius]

I updated my PR (#14025) and now it also supports expect.anything() and expect.any() inside an array.
Hopefully, I'll get any feedback soon as anyone who is using arrays as snapshots are stuck with Jest v29.0.3 for ~8 months now 🤞

[github-actions]

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[SimenB]

https://github.com/jestjs/jest/releases/tag/v29.6.0