Consider using doubling for escaping in `.literal = TRUE`

[gaborcsardi]

I am wondering if .literal = TRUE should still allow double delimiters for escaping. I.e. this currently fails:

❯ glue::glue("{'{'}", .literal = TRUE)
Error in glue_data(.x = NULL, ..., .sep = .sep, .envir = .envir, .open = .open,  :
  Expecting '}'

and AFAICT there is no easy way of writing a (non well formed) literal brace in a glue string, apart from using substitution:

❯ glue::glue("{'{{'}", .literal = TRUE)
Error in glue_data(.x = NULL, ..., .sep = .sep, .envir = .envir, .open = .open,  :
  Expecting '}'

As you might suspect this affects cli, because cli uses doubling as escaping currently, so it cannot switch to .literal = TRUE. On the other hand .literal = TRUE would be much better for the cases when people include literal quotes in the string, e.g. https://github.com/r-lib/cli/issues/370

If doubling is still accepted for escaping, then .literal = TRUE does not break cli, and I think it is also beneficial in general to be able to escape the delimiter.

[jennybc]

Can you point me to some of the cli revdep failures that inspired this? I realize you've given minimal examples above, but some even more realistic ones would be helpful for tackling this. So what sort of glue expressions are we talking about?

[gaborcsardi]

It is this from rlang:

mark_emph("{foo {}")
#> [1] "{.emph {\"{foo {}\"}}"

cli::format_message(mark_emph("{foo {}"))
#> Error in glue_data(.x = NULL, ..., .sep = .sep, .envir = .envir, .open = .open,  :
#>   Expecting '}'

But I am not concerned about the revdep failures too much. I am more concerned that with .literal = TRUE we cannot write (non well-formed) brace literals any more.

[hadley]

Closing since it looks like you handled this in cli.