[ruby-core:109344] [Ruby master Misc#18942] String splitting handling of empty fields is incorrect or insufficiently documented

Issue #18942 has been updated by scub8040 (Saverio M.).


austin (Austin Ziegler) wrote in #note-1:
> scub8040 (Saverio M.) wrote:
> > There are other cases though, which I think are either incorrectly handled, or at least, they should documented.
> 
> This is neither a behaviour bug nor a documentation bug.

Uh, ok! Thanks.

----------------------------------------
Misc #18942: String splitting handling of empty fields is incorrect or insufficiently documented
https://bugs.ruby-lang.org/issues/18942#change-98486

* Author: scub8040 (Saverio M.)
* Status: Open
* Priority: Normal
----------------------------------------
Hello!

The string splitting needs to deal with some edge cases when it comes to empty strings/fields, for example, an emptry string always returns an empty array.

There are other cases though, which I think are either incorrectly handled, or at least, they should documented.

The main case is a string exclusively composed of separators, e.g.:

```
"|||".split "|" # => []
```

Semantically speaking, such splitting does make sense, as an empty field is still a field. As the above example shows though, this returns an empty array (following the explained logic, it should return 4 empty strings).

IMO, this is incorrect. If for any reason this isn't, this should be documented though, as it's not obvious behavior (I've referred to this page: https://ruby-doc.org/core-3.0.0/String.html#method-i-split).

Things get even more obscure, when there are non-empty fields:

```
"||a|".split "|" # => ["", "", "a"]
```

This result is definitely inconsistent with both logics explained above:

- if empty fields should be treated as effective fields, the function should return ["", "", "a", ""]
- if empty fields should be ignored, it should return ["a"]

Considering this second case, I think that the function is buggy; there's no reason to treat differently the empty fields on the left of a non-empty field, from the ones on the right.

Even if this behavior is considered correct, I think it's very valuable to document such cases, as they're not intuitive, especially the second.



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