Using quantifiers in look-arounds (R/stringr) - r

Question

I'd like to extract the name John Doe from the following string:
str <- 'Name: | |John Doe |'
I can do:
library(stringr)
str_extract(str,'(?<=Name: \\| \\|).*(?= \\|)')
[1] "John Doe"
But that involves typing a lot of spaces, and it doesn't work well when the number of spaces is not fixed. But when I try to use a quantifier (+), I get an error:
str_extract(str,'(?<=Name: \\| +\\|).*(?= +\\|)')
Error in stri_extract_first_regex(string, pattern, opts_regex = opts(pattern)) :
Look-Behind pattern matches must have a bounded maximum length. (U_REGEX_LOOK_BEHIND_LIMIT, context=`(?<=Name: \| +\|).*(?= +\|)`)
The same goes for other variants:
str_extract(str,'(?<=Name: \\|\\s+\\|).*(?=\\s+\\|)')
str_extract(str,'(?<=Name: \\|\\s{1,}\\|).*(?=\\s{1,}\\|)')
Is there a solution to this?

Answer 1

How about:
First we remove Name
Then we replace all special characters with space
and finally str_squish it
Library(stringr)
str_squish(str_replace_all( str_remove(str, "Name"), "[^[:alnum:]]", " "))
[1] "John Doe"

Answer 2

Another solution using base R:
sub("Name: \\|\\s+\\|(.*\\S)\\s+\\|", "\\1", str)
# [1] "John Doe"

Answer 3

You might also use the \K to keep what is matched so far out of the regex match.
Name: \|\h+\|\K.*?(?=\h+\|)
Explanation
Name: \| match Name: |
\h+\| Match 1+ spaces and |
\K Forget what is matched so far
.*? Match as least as possible chars
(?=\h+\|) Positive lookahead, assert 1+ more spaces to the right followed by |
See a regex demo and a R demo.
Example
str <- 'Name: | |John Doe |'
regmatches(str, regexpr("Name: \\|\\h+\\|\\K.*?(?=\\h+\\|)", str, perl=T))
Output
[1] "John Doe"