<boolean> in l3keys

[jlaurens]

In l3prg <boolean> stands for "boolean variable" contrary to l3keys where <boolean> stands for "boolean value" (see .set_bool:N documentation)

Suggestion

Replace <boolean> with <boolean value> in l3keys (conforming to the error message below).
Moreover, in .set_bool:N, true and false really mean the strings "true" and "false" and not the booleans.
Adding quotes would help a lot.

A bug in an error message

MWE:

\documentclass{article}
\ExplSyntaxOn
\keys_define:nn { my } {
  key .bool_set:N = \g__my_bool,
  key .initial:n = \c_true_bool,
}
\keys_set:nn {my} {}
\ExplSyntaxOff
\begin{document}
ABC
\end{document}

The error message reads

! LaTeX3 error: Key '' accepts boolean values only.

The 'key' is missed. For .default:n instead of .initial:n, the 'key' is properly catched.

Suggestion: \bool_to_str:N and \bool_to_str:n would be welcome

It would simplify the use of <booleans> as <boolean values>.

key .initial:x = \bool_if:nTF {<boolean expression>} {true} {false}

would be replaced with

key .initial:x = \bool_to_str:n {<boolean expression>}

[blefloch]

I'm starting to make in an upcoming pull request most of the changes you suggested in various issues. I've added \bool_to_str:N and c and n analogues.

In l3prg <boolean> stands for "boolean variable" contrary to l3keys where <boolean> stands for "boolean value" (see .set_bool:N documentation)

No, in both cases <boolean> is a boolean variable like \l_foobar_bool. I've changed five occurrences to boolean value in l3keys to insist on that (and for consistency with other variable types in this file). I've added quotes as suggested around true and false.

bug in an error message

Thanks, it seems more general so I've logged it at #1013.

[blefloch]

Sorry for the noise, I'll close it with a commit comment, this way it will get closed once the pull request is merged.