UnhandledPromiseRejectionWarning after upgrade about pollyjs

[ericbiewener]

I find that this issue occurs if my test finishes before the polly request completes (in my use case, I don't care about the results of the request). I'm using setup-polly-jest and calling polly.flush() in Jest's afterEach() setup method seems to do the trick:

const { testPath } = global.jasmine;

Object.defineProperty(window, "fetch", { value: fetch, writable: true });
Polly.register(NodeHttpAdapter);
Polly.register(FSPersister);

const ctx = setupPolly({
  adapters: ["node-http"],
  persister: "fs",
  persisterOptions: {
    fs: {
      recordingsDir: path.resolve(testPath, "..", "./__recordings__"),
    },
  },
  matchRequestsBy: {
    headers: false,
    order: false,
  },
});

beforeEach(() => {
  global.polly = ctx.polly;
});

afterEach(async () => {
  await ctx.polly.flush()
});

[jasonmit]

@isi-gach thanks for letting us know!

1. What were you upgrading from? Knowing this will help me scope down the bug.
2. Besides the UnhandledPromiseRejectionWarning warnings, is your test behaving as expected?
3. Can you share your test code or reduce it down to something you can share?

Knowing all of this should help me replicate it and patch it for you.

[isi-gach]

@jasonmit

1. What were you upgrading from? Knowing this will help me scope down the bug.

I was using version 1.0.0 for adapter-fetch core and persister-fs

2. Besides the UnhandledPromiseRejectionWarning warnings, is your test behaving as expected?

Yes, all the tests pass, the only difference is the warning

3. Can you share your test code or reduce it down to something you can share?

I have been trying to extract the test to a new repository without success. The warning is triggered by the following line:

app.find('Button[content="HOME"]').simulate('click');

Button is redirecting to the home page using react-router

<Button content="HOME" onClick={() => history.push('/')} />

The warning disappear if I call await polly.flush() just before to polly.stop()
So it's not blocking me anymore. Maybe would be good to describe that workaround in the polly.js documentation?

[jasonmit]

Thanks for the feedback.

Let me know if you're able to reproduce at any point. In the meantime, I'll continue to think about the issue.

@isi-gach can you post the test itself? Curious what state Polly is in at the time and how it's being configured.

[isi-gach]

here you go:

import React from 'react';
import { mount } from 'enzyme';
import { Polly } from '@pollyjs/core';
import configService from '../../services/configService';
import PortalApp from '../../PortalApp';

describe('No Match page', () => {
    const polly = new Polly('NoMatch', { adapters: ['fetch'], persister: 'fs' });

    polly.configure({ mode: 'replay' });

    polly.server
        .get('/config.portal.json')
        .intercept((__, res) =>
            res.status(200).json({ ENV: 'development', SERVER_URL: 'http://localhost' }),
        );

    afterAll(() => polly.stop());

    it('display NoMatch after calling a bad Url', async () => {
        const config = await configService.getConfig();
        const app = mount(<PortalApp config={config} />);
        await polly.flush();
        app.find('Router[history]')
            .prop('history')
            .push('BadUrl');
        app.update();
        app.find('Button[content="HOME"]').simulate('click');
        expect(window.location.pathname).toBe('/');
        // return polly.flush();
    });
});

[jasonmit]

I'm still unable to reproduce it, but if you remove the await polly.flush() and uncomment the return polly.flush() does the issue still occur?

[isi-gach]

I get a slightly different warning:

(node:4154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'apply' of null
(node:4154) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 40)
(node:4154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'apply' of null
(node:4154) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 41)
(node:4154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'apply' of null
(node:4154) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 42)
(node:4154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'apply' of null
(node:4154) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 43)(node:4154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'apply' of null
(node:4154) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 44)
(node:4154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'apply' of null
(node:4154) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 45)
(node:4154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'apply' of null
(node:4154) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 46)
(node:4154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'apply' of null
(node:4154) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (reje
ction id: 47)
(node:4154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'apply' of null
(node:4154) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (reje
ction id: 48)
(node:4154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'apply' of null
(node:4154) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (reje
ction id: 49)
(node:4154) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'apply' of null
(node:4154) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (reje
ction id: 50)

maybe this issue could be related?

[jasonmit]

@isi-gach thanks again and sorry for all the back-and-forth.

I'll continue to think about this and try and reproduce on my end. If any future travelers have a reproduction please add to this issue!

[jasonmit]

Closing as the issue is old and awaiting on polly.flush() before your tests end should resolve this for most. If there are edge cases, feel free to open a new issue with clear instructions on how to reproduce.