substringBeforeLast

fun String.substringBeforeLast(
    delimiter: Char,
    missingDelimiterValue: String = this
): String
(source)
fun String.substringBeforeLast(
    delimiter: String,
    missingDelimiterValue: String = this
): String
(source)

Returns a substring before the last occurrence of delimiter. If the string does not contain the delimiter, returns missingDelimiterValue which defaults to the original string.