Stacktraces prevent Err instances being equal

[grodin]

This came up whilst writing tests. I wanted to assert that an Err instance was what I expected, using Vitest's expect/toEqual. That looks like:

expect(error).toEqual(Err(something))

and recursively compares error and Err(something) property by property.

This fails even when error is essentially identical to Err(something), because the _stack property isn't equal (and can't be).

The workaround is easy, just check and unwrap the Err, then compare the inner value, but it's a slight gotcha if you're not expecting it.

I think this and #77 suggest that maybe stacktrace capturing should be optional, though I'm not really sure what an ergonomic API for that would look like.

Thanks for maintaining this, btw. A Rust-like Result for TS is really useful!

[jstasiak]

Yeah that's a fair point, maybe a design decision we need to revisit.

We have a simple custom jest matcher that allows for expect(error).toEqualResult(Err(something)) but it's cumbersome (you need to remember to use it and it currently doesn't support all jest magic with something being a special matcher for example).