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gcanti
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 |
- Because that's the behaviour of
String.prototype.split. -
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
Checked out with test case by split from purescript-strings:
assertEqual
{ actual: S.split (Pattern "") ""
, expected: []
}
- Because that's the behaviour of
String.prototype.split.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.
When playing around with this case it becomes even more crazy. When we generalize the problem to input = separator we should actually return ['', ''] 😉
'a'.split('a') === ['', '']
''.split('') === [] // why?
It seems to be an edge case, but if when there is no higher intent for [''] we should go for [].
:trollface: https://github.com/denysdovhan/wtfjs#split-a-string-by-a-space