no-incorrect-deep-equal

📝 Disallow deepEqual/deepStrictEqual (and their notDeep* variants) when comparing with primitives.

💼 This rule is enabled in the following configs: ✅ recommended, ☑️ unopinionated.

🔧 This rule is automatically fixable by the --fix CLI option.

deepEqual and deepStrictEqual (and their notDeep* variants) perform deep structural comparison, which is unnecessary and misleading when one of the arguments is a primitive value. A primitive has no structure to recurse into, so strict equality is the correct and simpler assertion.

This rule reports deepEqual, deepStrictEqual, notDeepEqual, and notDeepStrictEqual calls where either argument is a primitive literal. It autofixes by replacing the method name with the strict equality equivalent.

Deep method	Replacement
deepEqual	equal
deepStrictEqual	strictEqual
notDeepEqual	notEqual
notDeepStrictEqual	notStrictEqual

Examples

import assert from 'node:assert';

// ❌
assert.deepEqual(actual, 'expected string');
assert.deepStrictEqual(42, actual);
assert.notDeepEqual(actual, null);

// ✅
assert.equal(actual, 'expected string');
assert.strictEqual(42, actual);
assert.notEqual(actual, null);

// ✅ (non-primitives — deep comparison is appropriate)
assert.deepEqual(actual, {key: 'value'});
assert.deepStrictEqual(actual, [1, 2, 3]);