object.filter'd objects fail strictEquals checks with normal object

Run the fail.js reproduction and inspect the implementation behind stdlib.object.filter, focusing on why its result differs from a normal object during strict equality checks. Done means the filtered result passes the shown toStrictEqual assertion against the equivalent POJO without changing the reported field values.

If you filter an object, and try to strictEqual it with a POJO with the filtered fields, the assertion fails.

import {expect} from '@playwright/test'
import stdlib  from '@logdna/stdlib'

const o = {
    field: 'val'
    , field2: 'val2'
}

const e = {field: 'val'}
const f = stdlib.object.filter(o, (k) => k !== 'field2')

console.log(e)
console.log(f)

expect(e).toStrictEqual(f)

I'm not sure where playwright gets it's expect library from, and couldn't find out with a few minutes of searching.

> node fail.js
{ field: 'val' }
[Object: null prototype] { field: 'val' }
/Users/jmoses/dev/logdna/qa-e2e-pipeline/node_modules/@playwright/test/lib/matchers/expect.js:131
      if (!testInfo) return matcher.call(target, ...args);
                                    ^

Ze [Error]: expect(received).toStrictEqual(expected) // deep equality

Expected: {"field": "val"}
Received: serializes to the same string
    at Proxy.<anonymous> (/Users/jmoses/dev/logdna/qa-e2e-pipeline/node_modules/@playwright/test/lib/matchers/expect.js:131:37)
    at file:///Users/jmoses/dev/logdna/qa-e2e-pipeline/fail.js:15:11
    at ModuleJob.run (node:internal/modules/esm/module_job:198:25)
    at async Promise.all (index 0)
    at ESMLoader.import (node:internal/modules/esm/loader:385:24)
    at loadESM (node:internal/process/esm_loader:88:5)
    at handleMainPromise (node:internal/modules/run_main:61:12) {
  matcherResult: {
    actual: { field: 'val' },
    expected: [Object: null prototype] { field: 'val' },
    message: '\x1B[2mexpect(\x1B[22m\x1B[31mreceived\x1B[39m\x1B[2m).\x1B[22mtoStrictEqual\x1B[2m(\x1B[22m\x1B[32mexpected\x1B[39m\x1B[2m) // deep equality\x1B[22m\n' +
      '\n' +
      'Expected: \x1B[32m{"field": "val"}\x1B[39m\n' +
      'Received: serializes to the same string',
    name: 'toStrictEqual',
    pass: false
  }
}

> npm list | grep -E 'playwright/test|logdna/stdlib'
├── @logdna/stdlib@1.2.0
├── @playwright/test@1.32.1