Expected behaviour of snapshot property matchers

[darrenbritton]

🐛 Bug Report

When using property matchers for snapshot testing, if a property matcher is defined within a nested object, then remaining properties are excluded from the generated snapshot.

To Reproduce

Steps to reproduce the behavior:

1. create a property matcher for a nested object, example:

 expect({ data: { foo: 'foo', bar: 'bar' }}).toMatchSnapshot({ data: { foo: expect.any(String) }});

2. resulting snapshot will not include bar: '' .e.g:

Object {
  "data": Object {
    "foo": Any<String>,
  },
}

Expected behavior

Expected the following snapshot to be generated:

Object {
  "data": Object {
    "foo": Any<String>,
	"bar": "bar",
  },
}

Link to repl or repo (highly encouraged)

recommended repl seems to be running Jest v22.1.2, so won't work here

Run npx envinfo --preset jest

Paste the results here:

  System:
    OS: macOS High Sierra 10.13.4
    CPU: x64 Intel(R) Core(TM) i7-5557U CPU @ 3.10GHz
  Binaries:
    Node: 8.9.0 - ~/.nvm/versions/node/v8.9.0/bin/node
    Yarn: 1.6.0 - /usr/local/bin/yarn
    npm: 5.5.1 - ~/.nvm/versions/node/v8.9.0/bin/npm
  npmPackages:
    jest: ^23.0.1 => 23.1.0 

[SimenB]

PR most welcome 🙂

@rickhanlonii Told you somebody would need it! :D

[darrenbritton]

Happy to give this a shot, any preference on the implementation? Should the default behaviour be updated, which will most likely break some existing use cases, or should this be a new method or something else entirely ?

[rickhanlonii]

Ah, yes, the difficulty here is doing a performant deep merge correctly. I ran into issues with symbols and prototypes when trying to fix this, happy to see someone else give it a shot!

I would say this is a bug fix for the default behavior and push in a minor release (though that may require some snapshot updates, I think that's better than waiting for the next major)

[andys8]

Fixing this would be very welcome. Until I found this issue, I thought I'm missing something.

[darrenbritton]

Pretty swamped in work but managed to take a look for a few hours. Tried utilising the deep merge from some other library's but with no success, I can't even get the relevant tests to pass locally, hard to say when I'll have the time to look at this again so if anyone else wants to give it a go, feel free!

[WaldoJeffers]

I might look into this. I'm having the same issue, and it can be misleading because the test passes, but the snapshot does not store what you think it does (it only stores the custom matchers), making the test quite inefficient.

[swcisel]

@WaldoJeffers I have a PR out for this issue. Would you want to take a look at it and let me know what you think? I’d really appreciate any feedback people can give me, as it’s my first PR to this project.

[github-actions]

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