R: Regex to match more than one pipe occurrence - r

Question

I have a dataset in which I paste values in a dplyr chain and collapse with the pipe character (e.g. " | "). If any of the values in the dataset are blank, I just get recurring pipe characters in the pasted list.
Some of the values look like this, for example:
badstring = "| | | | | | GHOULSBY,SCROGGINS | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | CAT,JOHNSON | | | | | | | | | | | | BURGLAR,PALA | | | | | | | | |"
I want to match all the pipes that occur more than once and delete them, so that just the names appear like so:
correctstring = "| GHOULSBY,SCROGGINS | CAT,JOHNSON | |BURGLAR,PALA |"
I tried the following, but to no avail:
mutate(names = gsub('[\\|]{2,}', '', name_list))

Answer 1

The difficulty in this question is in formulating a regex which can selectively remove every pipe, except the ones we want to remain as actual separators between terms. We can match on the following pattern:
\|\s+(?=\|)
and then replace just empty string. This pattern will remove any pipe (and any following whitespace) so long as what follows is another pipe. A removal would not occur when a pipe is followed by an actual term, or when it is followed by the end of the string.
badstring = "| | | | | | GHOULSBY,SCROGGINS | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | CAT,JOHNSON | | | | | | | | | | | | BURGLAR,PALA | | | | | | | | |"
result <- gsub("\\|\\s+(?=\\|)", "", badstring, perl=TRUE)
result
[1] "| GHOULSBY,SCROGGINS | CAT,JOHNSON | BURGLAR,PALA |"
Demo
Edit:
If you expect to have inputs like | | | which are devoid of any terms, and you would expect empty string as the output, then my solution would fail. I don't see an obvious way to modify the above regex, but you can handle this case with one more call to sub:
result <- sub("^\\|$", "", result)
We also might be able to modify the original pattern to use an alternation covering all cases:
result <- gsub("\\|\\s+(?=\\|)|(?:^\\|$)", "", badstring, perl=TRUE)