builtin,js: implement JS string.split_any

[juan-db]

Implement string.split_any for the JS backend.

This PR fixes #21440.

[JalonSolov]

In the string 2345, there is nothing after the 5, therefore nothing to split. The only splits would be between 2 and 3, 3 and 4, and 4 and 5.

The only thing after the 5, is the NUL at the end, which is not a "real" character.

[JalonSolov]

Doing it like this is just as bad as the Go utils.TrimSplit() function... if you call that on an empty string, it does NOT return an empty array... it returns an array with one element, and that element is ''.

[juan-db]

In the string 2345, there is nothing after the 5, therefore nothing to split. The only splits would be between 2 and 3, 3 and 4, and 4 and 5.

The only thing after the 5, is the NUL at the end, which is not a "real" character.

What is the V version splitting in the 1213.split_any('1') case then to give ['', '2', '3']? Nothing precedes the first character in the string.

[JalonSolov]

It split with 1 as the delimiter. Since there was only an "empty string" before the first delimiter, that's all it gave.

Same as ';2;3'.split_any(';')

[juan-db]

I understand that reasoning, but it feels like that's more driven by implementation result than actual intention.

The most common use case I know for split is for CSV values. In these cases, you expect it to split the string every time it encounters the delimiter.

E.g. if you had the following CSV:

person,start,end,role,earnings,manager
john,2015,,founder,1USD,

you'd want to reliably and conveniently extract each field.

split_any is a more niche version so I don't really know what the most common use case for it would be over regular split, but either way I believe the behavior should be consistent.

[JalonSolov]

The difference is in the description of split_any...

Split a string using the chars in the delimiter string as delimiters chars.

Meaning, you can include several different delimiters, and it will split on all of them.

println('12;34:56^78,'.split_any(';:^,'))

output is

['12', '34', '56', '78']

Obviously contrived, but suppose you had a timestamp in a log file, and wanted to split the pieces... with split_any you could split them all in one call, instead of separate calls with each different separator, and trying to figure it out from there...

println('[2024-05-31_19:39:23] This is the log message.'.split_any('[-_:]'))

output is

['', '2024', '05', '31', '19', '39', '23', ' This is the log message.']

... and in this case, I'd have to agree... the '' as the first entry looks like a bug to me.

[juan-db]

I'm not sure how to proceed in this case because the suggested behavior is contrary to all my experiences with other languages and isn't consistent with the regular split behavior where it overlaps in concept.

In rough pseudocode, this seems like the correct simplified example to me.

output := []
buffer := ''

for c in str:
    if c == delim
        // *any* time we encounter delimiter, *split the string*
        output << buffer
        buffer = ''
    else
        buffer += c

output << buffer // make sure everything after the last delimiter is included

// for the suggested solution, instead of the above, we would have to handle
// the end of the string as a special case
/*
if buffer.len != 0 {
    output << buffer
}
*/

return output

[juan-db]

I don't hold much authority here, so I think either someone needs to decide it's more important to keep the existing V behavior, or we need more input on what the expected behavior should be.

[JalonSolov]

The expected behavior is that all backends should produce exactly the same results.

If anything is changed, then all backends should be changed so that the above statement is still true.

[spytheman]

Here is a plan of action:

1. Make the JS version match the V version, so that the existing PR can be merged, without breaking existing code
2. Make another PR, that changes the behavior of both the pure V and the JS versions to what you think is a more useful behavior (that would be a breaking change, but it will be caught by the CI, and we can test and discuss it extensively there).

[spytheman]

Excellent work.