'to satisfy' with circular data causes "Maximum call stack size exceeded" #694
Comments
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Did a bit of debugging and turns out the same happens with any circular structure ( it('fails for circular structures with "Maximum call stack size exceeded"', () => {
const circular = {};
circular.loop = circular;
const circular2 = {};
circular2.loop = circular2;
expect(circular, 'to satisfy', circular2);
});Not sure what unexpected is expected to do with circular structures, the docs don't say anything about this. |
salomvary
changed the title
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Hmm, yeah, we don't guard against circularity in the right hand-side of It works fine with a circular subject: const expect = require('unexpected');
const circular = {};
circular.a = circular;
expect(circular, 'to satisfy', {a: {a: {a:{}}}}); // :+1:
expect(circular, 'to satisfy', {a: {a: {b:{}}}});We can probably fix this, but I'm wondering what your use case is? 🤔 |
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Hi @papandreou, thanks for the quick response! I am honored to be the first person throwing a circular structure on the right side of an expectation ;) My use case was verifying a piece of code that was doing something like this: const form = new FormData()
form.append('some', 'value')
fetch('some/url', {method: 'post', body: form})using an expectation roughly like: const expectedForm = new FormData()
expectedForm.append('some', 'value')
expect(fetchOptions, 'to satisfy', {method: 'post', body: expectedForm})Turns out FormData is internally implemented in a circular way (at least in jsdom), entries having a reference to the FormData instance or something like that. (This was unknown to me.) As someone not particularly familiar with unexpected and contributing to a codebase with it already in place, I expected this assertion to either work or shout at me for FormData not being supported. Shouting at me would have not surprised me, I understand supporting any type all the supported JS engines have built in is not feasible. As this might be a usage edge case fixing should also not be urgent. I did poke around in the source but saw no obvious fix (but have never seen unexpected "from inside" before). Also, now that I understand what the problem is I can come up with other ways of verifying behavior in my use case. |
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We don't support this in in |
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Upssy, you can't get at the fields. Let me brew something up for you. |
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Try to add the following type to unexpected: expect.addType({
name: 'FormData',
base: 'wrapperObject',
identify(value) {
return value && value instanceof FormData;
},
prefix: (output, value) => output.jsFunctionName('FormData').text('('),
suffix: (output, value) => output.text(')'),
unwrap: form => {
const result = {};
Array.from(form.entries()).forEach(([key, value]) => {
if (typeof result[key] === 'undefined') {
result[key] = value;
} else if (typeof result[key] === 'string') {
result[key] = [result[key], value];
} else {
result[key].push(value);
}
});
return result;
}
});Then something like this: const a = new FormData();
a.append('foo', 'bar');
a.append('foo', 'quz');
a.append('bar', 'baz');
expect(a, 'to satisfy', {
foo: ['bar', 'qux'],
bar: 'baz'
});will fail with a diff like this:
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You can also simplify it to just return the entries as an array if the order matters to you. |
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@sunesimonsen That looks quite neat, thanks for the suggestion. 👍
If there is an easy fix to avoid "Maximum call stack size exceeded" and fail with a helpful message on circular data, that would be nice. |
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@salomvary I agree that it would be a good idea to detect circular data or the right hand side of the to satisfy assertion. |
Given this added to test/unexpected.spec.js:
npx jest -- test/unexpected.spec.json the latestmasterof this repo fails with an exception:Using Node.js v12.14.1.
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