Split with a multicharacter regex pattern and keep delimiters - regex

Question

I have next string and regex for splitting it:
val str = "this is #[loc] sparta"
val regex = "((?<=( #\\[\\w{3,100}\\] ))|(?=( #\\[\\w{3,100}\\] )))"
print(str.split(Regex(regex)))
//print - [this is, #[loc] , sparta]
Works fine. But in develop I did not realize when in #[***] block must be a not only text (\w) - he have and "-" and numbers (UUID), and my correct blocks is -
val str = "this is #[loc_75acca83-a39b-4df1-8c3c-b690df00db62]"
and in this case regex don't work.
How to change this part - "\w{3,100}" for new requirements?
I try change to any - "\.{3,100}" - not work

Answer 1

To fix your issue, you may replace your regex with
val regex = """((?<=( #\[[^\]\[]{3,100}] ))|(?=( #\[[^\]\[]{3,100}] )))"""
The \w can be replaced with [^\]\[] that matches any char but [ and ].
Note the use of a raw string literal, """...""", that allows the use of a single backslash as a regex escape.
See the Kotlin online demo.
Alternatively, you may use the following method to split and keep delimiters:
private fun splitKeepDelims(s: String, rx: Regex, keep_empty: Boolean = true) : MutableList<String> {
var res = mutableListOf<String>() // Declare the mutable list var
var start = 0 // Define var for substring start pos
rx.findAll(s).forEach { // Looking for matches
val substr_before = s.substring(start, it.range.first()) // // Substring before match start
if (substr_before.length > 0 || keep_empty) {
res.add(substr_before) // Adding substring before match start
}
res.add(it.value) // Adding match
start = it.range.last()+1 // Updating start pos of next substring before match
}
if ( start != s.length ) res.add(s.substring(start)) // Adding text after last match if any
return res
}
Then, just use it like
val str = "this is #[loc_75acca83-a39b-4df1-8c3c-b690df00db62] sparta"
val regex = """#\[[\]\[]+]""".toRegex()
print(splitKeepDelims(str, regex))
// => [this is , #[loc_75acca83-a39b-4df1-8c3c-b690df00db62], sparta]
See the Kotlin demo.
The \[[^\]\[]+] pattern matches
\[ - a [ char
[^\]\[]+ - 1+ chars other than [ and ]
] - a ] char.