Jest: toMatchInlineSnapshot fails if prettier's native module deps are mocked through jest.mock

[tryggvigy]

🐛 Bug Report

toMatchInlineSnapshot fails if path module is mocked

jest.mock('path', () => ({}));

test('foo', () => {
  expect({}).toMatchInlineSnapshot();
});

results in

● Test suite failed to run

    TypeError: path.resolve is not a function

Run npx envinfo --preset jest

Paste the results here:

  System:
    OS: macOS High Sierra 10.13.5
    CPU: x64 Intel(R) Core(TM) i7-6567U CPU @ 3.30GHz
  Binaries:
    Node: 8.9.4 - ~/.nvm/versions/node/v8.9.4/bin/node
    Yarn: 1.7.0 - /usr/local/bin/yarn
    npm: 5.6.0 - ~/.nvm/versions/node/v8.9.4/bin/npm
  npmPackages:
    jest: ^23.4.0 => 23.4.0

[SimenB]

I wonder if this might be fixed by #6687?

@aaronabramov wdyt?

EDIT: Hmm, no. I tried applying that patch locally, and it still fails 🙁

[aaronabramov]

no, this seems like a separate issue, but comes from the same bug.
right now we're trying to do too much from within the VM. we need to take absolutely everything out of there except the snapshot state object at some point

[tryggvigy]

I'm trying to dig into this. I've got a test that reproduces the bug in e2e/__tests__/to_match_inline_snapshot.test.js.

The error is coming from the compiled node_modules/prettier/third-party.js and originally from this line in cosmiconfig dependency. Thats the code thats trying to run when TypeError: path.resolve is not a function happens.

---

node_modules/prettier/prettier-bin.js is right now using these native modules

var path = _interopDefault(require('path'));
var os = _interopDefault(require('os'));
var assert = _interopDefault(require('assert'));
var fs = _interopDefault(require('fs'));
var util = _interopDefault(require('util'));
var events = _interopDefault(require('events'));
var thirdParty = require('./third-party');
var thirdParty__default = thirdParty['default'];
var readline = _interopDefault(require('readline'));
// and these two through ./third-party
var stream = _interopDefault(require('stream'));
var module$1 = _interopDefault(require('module'));

I'm assuming jest.mock will overrider any of the above. I'm unsure how to actually fix this issue (looking at https://github.com/facebook/jest/pull/6687 for inspiration) but I'll keep digging. I'd appreciate any input from folks with more context.

update jest.mock only causes failure on some of them

mock path -- TypeError: path.resolve is not a function
mock fs -- TypeError: fs.statSync is not a function
mock os -- TypeError: os.homedir is not a function
mock assert -- TypeError: assert is not a function
mock utils -- passes
mock readline -- passes
mock stream -- passes
mock module -- passes

[aaronabramov]

@tryggvigy hey! the issue comes from the fact that we have two environments we execute Jest code in:

1. Outer environment, where all framework code is running
2. Test environment inside a VM https://github.com/facebook/jest/blob/master/packages/jest-environment-node/src/index.js#L94

because most of our framework code is in the outer environment we're able to mock native/whatever modules from inside the VM and not affect the framework code.

unfortunately inline snapshots bring a lot of logic that is executed in the inner scope (inside the VM) and interacting with the environment makes it possible to break framework code.

the right fix for this is to take everything framework related to the outer scope and pass a pure/stateless function to the VM

[aaronabramov]

@tryggvigy actually! since you found that the issue comes from inside prettier my PR might have fixed it (cause i did take prettier to the outer scope)
do you mind checking out master and trying to reproduce it?

[tryggvigy]

Thanks for explaining @aaronabramov! Also, unfortunately yes I can reproduce this on master.

Here is the test I added to e2e/__tests__/to_match_inline_snapshot.test.js and reproduces the bug on latest master.

test('fails', () => {
  const filename = 'mockFail.test.js';
  const test = `
    jest.mock('path', () => ({}));
    test('hæhæ!', () => {
      expect({}).toMatchInlineSnapshot();
    });
  `;

  writeFiles(TESTS_DIR, {[filename]: test});
  const {stderr, status} = runJest(DIR, ['-w=1', '--ci=false', filename]);
  expect(stderr).toMatch('1 snapshot written from 1 test suite.');
  expect(status).toBe(0);
});

[tryggvigy]

I noticed that this is not an issue in jest-circus.
When run with JEST_CIRCUS=1, this passes.

[aaronabramov]

ugh.. that might be my fault :)
i did use require for babel-traverse, but kept localRequire for prettier
https://github.com/facebook/jest/blob/master/packages/jest-jasmine2/src/setup_jest_globals.js#L105
i'm pretty sure that's the reason

[tryggvigy]

Yeah, thats it :) Test passes now, I'll make a PR

https://github.com/facebook/jest/pull/6776

[tryggvigy]

Closing the issue. It's fixed once #6776 is merged

[aaronabramov]

@tryggvigy thanks for digging into it! :)