Pluralization with empty last alternative produces the wrong output

[rundel]

I have a slightly odd use case where I was trying to "pluralize" the verb exist and ran into the an issue where {?s/} is being treated as {?s}.

vars = c("X")
cli::cli_text("{vars} exist{?s/}")
#> X exist
cli::cli_text("{vars} exist{?s}") 
#> X exist

vars = c("X","Y")
cli::cli_text("{vars} exist{?s/}")
#> X and Y exists
cli::cli_text("{vars} exist{?s}") 
#> X and Y exists

it seems like this may be a more general issue with a trailing empty alternative:

vars = c()
cli::cli_text("{vars} word{?A/B/C}") # Ok
#> wordA
cli::cli_text("{vars} word{?/B/C}")  # Ok
#> word
cli::cli_text("{vars} word{?A//C}")  # Ok
#> wordA
cli::cli_text("{vars} word{?A/B/}")  # Wrong
#> wordB

vars = c("X")
cli::cli_text("{vars} word{?A/B/C}") # Ok
#> X wordB
cli::cli_text("{vars} word{?/B/C}")  # Ok
#> X wordB
cli::cli_text("{vars} word{?A//C}")  # Ok
#> X word
cli::cli_text("{vars} word{?A/B/}")  # Wrong
#> X wordA

vars = c("X","Y")
cli::cli_text("{vars} word{?A/B/C}") # Ok
#> X and Y wordC
cli::cli_text("{vars} word{?/B/C}")  # Ok
#> X and Y wordC
cli::cli_text("{vars} word{?A//C}")  # Ok
#> X and Y wordC
cli::cli_text("{vars} word{?A/B/}")  # Wrong
#> X and Y wordB

[gaborcsardi]

Seems like a bug indeed. A (not very elegant) workaround for now is

> cli::cli_text("{letters[1]} {?exists/exist}")
a exists
> cli::cli_text("{letters[1:3]} {?exists/exist}")
a, b, and c exist

[gaborcsardi]

This is because I did not expect strsplit() to drop that last empty string:

> strsplit("A/B/", "/", fixed = TRUE)[[1]]
[1] "A" "B"