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`toEqual` does not treat non-enumerable properties equally #6392

mweststrate opened this Issue Jun 4, 2018 · 1 comment


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mweststrate commented Jun 4, 2018

馃悰 Bug Report

I discovered some inconsistent behavior in the toEqual matcher in Jest; when comparing to objects, it ignores non-enumerable properties, but only if they are not symbols. This leads to quite inconsistent behavior:

This test passes:

const actual1 = {
        x: 3
Object.defineProperty(actual1, "test", {
        enumerable: false,
        value: 5
expect(actual1).toEqual({ x: 3 })

But this one doesn't:

const actual2 = {
        x: 3
const mySymbol = Symbol("test")
Object.defineProperty(actual2, mySymbol, {
        enumerable: false,
        value: 5
expect(actual2).toEqual({ x: 3 })

Where one would expect both to behave the same.

The cause of the issue can be found here. To find the string properties the loop is used which ignores non-enumerable properties, but for the symbolic properties getOwnPropertySymbols is used, which will include non-enumerable properties.

To Reproduce

See link below

Expected behavior

Non-enumerable symbolic properties should be treated the same as non-enumerable non-symbolic properties when running toEqual. Either both should be included, or excluded. Given that symbolic properties are lot more exotic, I think the behavior of string properties should be followed and non-enumerable symbolic properties should be excluded from deep equality.

I am willing to file a PR myself

Link to repl or repo (highly encouraged)

Run npx envinfo --preset jest

Paste the results here:

    OS: Linux 4.15 Ubuntu 18.04 LTS (Bionic Beaver)
    CPU: x64 Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz
    Node: 9.3.0 - ~/.nvm/versions/node/v9.3.0/bin/node
    Yarn: 1.6.0 - /usr/bin/yarn
    npm: 5.5.1 - ~/.nvm/versions/node/v9.3.0/bin/npm
    @types/jest: ^21.1.9 => 21.1.10 
    jest: ^22.0.4 => 22.4.4 

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mweststrate commented Jun 5, 2018

Added PR: #6398, as that is often more clarifying than a bug report :)

@cpojer cpojer closed this in #6398 Jun 5, 2018

cpojer added a commit that referenced this issue Jun 5, 2018

Fix: `expect` no longer tries to equal non-enumerable symbolic proper鈥
鈥ies.鈥 (#6398)

* `expect` no longer tries to equal non-enumerable symbolic properties. Fixes #6392

* Updated changelog with PR number

* Fixed linting errors

* 'fixed' jest error
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