iterables and toHaveBeenCalledWith result in RangeError: Maximum call stack size exceeded

[sorawee]

🐛 Bug Report

If toHaveBeenCalledWith is used with an iterable, RangeError: Maximum call stack size exceeded will be thrown.

To Reproduce

Steps to reproduce the behavior:

Run

class Blah {
  *[Symbol.iterator]() {
    yield this;
  }
}

const video = {
  play(x) {
    console.log('received', x);
    return true;
  },
};

test('plays video', () => {
  const val = new Blah();
  const spy = jest.spyOn(video, 'play');
  const isPlaying = video.play(val);

  expect(spy).toHaveBeenCalledWith(val);
  expect(isPlaying).toBe(true);
});

This results in:

 FAIL  __tests__/test.js
  ● Console

    console.log __tests__/test.js:9
      received Blah {}

  ● plays video

    RangeError: Maximum call stack size exceeded

      17 |   const isPlaying = video.play(val);
      18 | 
    > 19 |   expect(spy).toHaveBeenCalledWith(val);
         |               ^
      20 |   expect(isPlaying).toBe(true);
      21 | });
      22 | 

      at Object.toHaveBeenCalledWith (__tests__/test.js:19:15)

Test Suites: 1 failed, 1 skipped, 1 of 2 total
Tests:       1 failed, 17 skipped, 18 total
Snapshots:   0 total
Time:        1.401s, estimated 2s
Ran all test suites.

Expected behavior

The test passes.

Link to repl or repo (highly encouraged)

Code given above

Run npx envinfo --preset jest

Paste the results here:

It results in an error for me. I don't think it's what you want, but I will paste it here anyway.

(node:27012) UnhandledPromiseRejectionWarning: TypeError: Cannot read property '1' of null
    at a.run.then.e (/home/user/.npm/_npx/27012/lib/node_modules/envinfo/dist/cli.js:2:96634)
(node:27012) 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: 1)
(node:27012) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Here's the version in package.json

"jest": "^23.5.0",

[sorawee]

Note that yield this is crucial here. Yielding something else like 0 won't cause a problem.

[SimenB]

Minimum reproduction in Jest's own test suite:

diff --git i/packages/expect/src/__tests__/utils.test.js w/packages/expect/src/__tests__/utils.test.js
index 6a5e7d909..8ba302d89 100644
--- i/packages/expect/src/__tests__/utils.test.js
+++ w/packages/expect/src/__tests__/utils.test.js
@@ -13,6 +13,7 @@ const {
   emptyObject,
   getObjectSubset,
   getPath,
+  iterableEquality,
   subsetEquality,
 } = require('../utils');
 
@@ -150,3 +151,17 @@ describe('subsetEquality()', () => {
     expect(subsetEquality(undefined, {foo: 'bar'})).not.toBeTruthy();
   });
 });
+
+describe('iterableEquality()', () => {
+  test('self-returning iterator does not explode', () => {
+    class Iter {
+      *[Symbol.iterator]() {
+        yield this;
+      }
+    }
+
+    const val = new Iter();
+
+    expect(iterableEquality(val, val)).toBe(true);
+  });
+});

From what I can understand it recurses forever here: https://github.com/facebook/jest/blob/c9893d2f1cdbc98655ca446d2a49f8c77a42b4be/packages/expect/src/utils.js#L183-L188

Not sure how to handle it. Bail after say 1000 iterations? If val.next() returns val? If it returns itself n amounts of times?

[SimenB]

@thymikee @rickhanlonii thoughts?

[sorawee]

I'm no expert about this, but would checking reference equality helps?

[SimenB]

Yeah, I think so. But for how many iterations should we do that before bailing? Maybe somebody has an iterator delivering fibonacci numbers - there are cases for infinite generators. Not sure what would give the best DX here

[rickhanlonii]

I think bailing after 1000 makes sense, we can up it if necessary

[gamaamaral98]

Hi, I am a student of computer and software engineering and I choose this issue to work on in my software engineering subject so I'm no expert on this. As I was trying to understand this issue I looked into the comments and saw that the problem may be fixed if the cycle referenced above is changed. Would you give me some tips and help? Thanks a lot!

[github-actions]

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