Underscore in named group matching

[DSLituiev]

I am trying to match a named group and running into a behaviour that does not seem to be properly documented.

filnames = c("a","b", "c")

pattern_regex <- (?<my_variable>[a-zA_\\-]+)"

str_match(filnames, pattern_regex)

Error in stri_match_first_regex(string, pattern, opts_regex = opts(pattern)) : 
  Invalid capture group name. (U_REGEX_INVALID_CAPTURE_GROUP_NAME, context= ...

There is no documentation that says underscores are unsupported, and given it's a common practice in other languages, like python re, I assumed it should have worked. The error message is not helpful either

[gagolews]

Please see the documentation of the underlying stringi package:

https://stringi.gagolewski.com/rapi/about_search_regex.html:

(?<name>...): Named capture group, where name (enclosed within the angle brackets) is a sequence like [A-Za-z][A-Za-z0-9]*

[hadley]

Thanks @gagolews!