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Incorrect result from isDeepStrictEqual on two different Sets #61386
Description
Version
22.21.1
Platform
Microsoft Windows NT 10.0.19045.0 x64
Subsystem
util
What steps will reproduce the bug?
The problem can be seen in a quick REPL session:
Welcome to Node.js v22.21.1.
Type ".help" for more information.
> a = new Set([0, new Set([1, 2, 3]), new Set([4, 5, 6])])
Set(3) { 0, Set(3) { 1, 2, 3 }, Set(3) { 4, 5, 6 } }
> b = new Set([0, new Set([1, new Set([2, 3]), new Set([20, 30])]), new Set([4, new Set([5, 6]), new Set([50, 60])])])
Set(3) {
0,
Set(3) { 1, Set(2) { 2, 3 }, Set(2) { 20, 30 } },
Set(3) { 4, Set(2) { 5, 6 }, Set(2) { 50, 60 } }
}
> require('util').isDeepStrictEqual(a, b)
true
How often does it reproduce? Is there a required condition?
Interestingly, require('util').isDeepStrictEqual(b, a) returns false, as expected. Which indicates that isDeepStrictEqual is not symmetrical.
What is the expected behavior? Why is that the expected behavior?
The result should be false.
What do you see instead?
I'm seeing true.
Additional information
No response
Activity
ljharb commentedon Jan 14, 2026
I wouldn't expect any of those to return true, personally -
new Set([1, 2])andnew Set([1, new Set(2)])aren't the same.DoubleClickPreferred commentedon Jan 14, 2026
With these two inputs, isDeepStrictEqual works as expected:
It looks like the bug happens with deeper sets.
ljharb commentedon Jan 14, 2026
I mean it's clearly a bug - but "strict deep equal" shouldn't be equating
new Set(xs)withxsin the first place.BridgeAR commentedon Jan 15, 2026
This is a case specific to mixed primitive / object cases. I will open a fix tomorrow, I identified the issue in the code. It also applies the same to maps.
assert,util: fix deep comparison for sets and maps with mixed types
assert,util: fix deep comparison for sets and maps with mixed types
assert,util: fix deep comparison for sets and maps with mixed types
assert,util: fix deep comparison for sets and maps with mixed types
assert,util: fix deep comparison for sets and maps with mixed types
assert,util: fix deep comparison for sets and maps with mixed types
assert,util: fix deep comparison for sets and maps with mixed types
assert,util: fix deep comparison for sets and maps with mixed types
assert,util: fix deep comparison for sets and maps with mixed types