Why does `string.split` return non-empty array when given an empty string?

🐛 Bug report

Current Behavior

String.prototype.split:

''.split('') // => []

fp-ts:

pipe('', string.split('')) // => ['']

Expected behavior

I would expect [] from string.split, so it matches String.prototype.split but also because I think that behaviour makes more sense.

It seems like this was done intentionally: https://github.com/gcanti/fp-ts/commit/7d1887de8b704b6dc86a29964c33f6ca8decb41a#diff-bbade37cef19cf470364082a01329d9fbf208a96862818d50ea97602767d7a48R130

What was the reasoning for this change?

Reproducible example

See above.

Suggested solution(s)

Additional context

Your environment

Which versions of fp-ts are affected by this issue? Did this work in previous versions of fp-ts?

Software	Version(s)
fp-ts
TypeScript

[imcotton]

:trollface: https://github.com/denysdovhan/wtfjs#split-a-string-by-a-space

[enricopolanski]

1. Because that’s the behaviour of String.prototype.split.
2. pipe('ab', string.split('')) returns ['a', 'b'], which suggests that a '' separator will split each character, but if '' is the input, there are no characters to split

I don’t see why is that relevant what the native api does. 🤷

I think we’re reframing the classical question of “does the empty set contains itself”. I think both of the choices are okay and it’s more of a design question than a bug.