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assert.deepEqual assertion error depth limit #15696

Description

@caub

I think it would be better if the message of assert.deepEqual was not limited to a depth of 3, and could display the first difference between the objects, like some testing libraries do

const assert = require('assert');

assert.deepEqual({
	foo: {
		bar: {
			qux: {
				lolcat: {
					bip: {
						yup: 56
					}
				}
			}
		}
	}
}, {
	foo: {
		bar: {
			qux: {
				lolcat: {
					bip: {
						yup: 56.3
					}
				}
			}
		}
	}
})

// outputs:
// AssertionError [ERR_ASSERTION]: { foo: { bar: { qux: [Object] } } } deepEqual { foo: { bar: { qux: [Object] } } }

A simple implementation example:

const deepEq = (o1, o2) => {
	const keys1 = Object.keys(o1);
	const keys2 = Object.keys(o2);
	if (keys1.length !== keys2.length) {
		assert.deepEqual(o1, o2);
	}
	for (let i=0; i<keys1.length; i++) {
		const v1 = o1[keys1[i]], v2 = o2[keys1[i]];
		if (v1 && typeof v1 === 'object') {
			deepEq(v1, v2);
		} else {
			assert.equal(v1, v2);
		}
	}
};

The current implementation passes the entire objects in the Error, and .toString is limited in 3 in depth I guess

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