div fences are capped at 80 characters

[zkamvar]

Problem

As reported in carpentries/workbench#62, if someone writes a closing div fence that is more than 80 characters wide, they encounter an error of a missing div tag.

I can construct a reproducible example that demonstrates this pattern with 91 closing colons:

:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: instructor

test

:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

tmp <- withr::local_tempfile()
open <- paste(paste(rep(":", 80), collapse = ""), "instructor")
close <- paste(rep(":", 91), collapse = "")
writeLines(c(open, "\ntest\n", close), tmp)
pegboard::Episode$new(tmp)$label_divs()
#> ✖ A section (div) tag mis-match was detected.
#> ✖ There are not enough close tags (0) for the number of open tags (2).
#> Error: Missing close section (div) tag in /tmp/RtmpBS9YrF/file8e3174daa911.
#> Here is a list of all the tags in the file:
#> /tmp/RtmpBS9YrF/file8e3174daa911:1   | tag: instructor
#> /tmp/RtmpBS9YrF/file8e3174daa911:5   | tag: :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

^{Created on 2023-06-29 with reprex v2.0.2}

Explanation

The reason for this is because the regex (yes, we use regex for this 😨) caps the number of colons at 80 (important part is [:]{3,80}$):

pegboard/R/div.R

Lines 658 to 660 in 3b06f45

	div_close_regex <- function() {
	"(^ *?[<][/]div[>] *?\n?$|^[:]{3,80}$)"
	}

Note, however that this cap is NOT present in the opening div regex (which is even more horrifying than the previous; so much so that it needs 20 lines of explanation) (important part is [:]{3,}):

pegboard/R/div.R

Line 655 in 3b06f45

trimws(sub('^(.+?class[=]["\']|[:]{3,}?\\s*?[{]?\\s*?[.]?)([-a-zA-Z0-9]+).*(["\'].+?|.*?[}]?[:]*?)$', '\\2', div))