Annoying syntax highlighting of unclosed group at \cs:w

Question

So I was looking at my preamble, with Overleaf yelling at me for not putting a closing bracket after the piece of code attached below, which is strange, since that group is indeed closed. To confirm, I removed several commands until I realised that the problem arose on line 6 with \cs:w.

Any thoughts?

\ExplSyntaxOn
\NewDocumentCommand{\newenvcommand}{ m m } % #1 = env name, #2 = command name
{
    \cs_if_exist:cF { g_envc_#1_list_tl } { \tl_new:c { g_envc_#1_list_tl } }
    \tl_gput_right:cn { g_envc_#1_list_tl } { #2 }
    \exp_after:wN \newcommand \cs:w envc_#1_\cs_to_str:N #2 \cs_end:
}
\NewDocumentCommand{\checkenvcommands}{ }
{
    \cs_if_exist:cT { g_envc_\use:c {@currenvir} _list_tl }
    {
        \tl_map_inline:cn { g_envc_\use:c {@currenvir} _list_tl }
        {
            \cs_set_eq:Nc ##1 { envc_\use:c {@currenvir} _\cs_to_str:N ##1 }
        }
    }
}
\ExplSyntaxOff

Answer 1

(I'm on support staff at Overleaf.)

The code aspects have already been addressed in another answer. I'll focus on "Overleaf yelling at you" :-).

Overleaf uses chktex as the in-editor syntax checker. This works well for typical documents. But if you have certain TeX programming constructs in your code, chktex can report false positives, where valid code is flagged as an error.

You can use a few strategies to disable the syntax checker for problematic parts of your project:

1. You can disable code check entirely in the project settings (Overleaf menu on the upper left).
2. You can disable code check for a particular file by adding %%novalidate as the first line of the file.
3. You can disable code check for portions of a file by surrounding the lines to ignore with %%begin novalidate and %%end novalidate.

Source: Code Check on Overleaf

Answer 2

I don't know about Overleaf yelling at you. But you can surely avoid it by using better code:

\ExplSyntaxOn
\NewDocumentCommand{\newenvcommand}{ m m } % #1 = env name, #2 = command name
{
    \tl_if_exist:cF { g_envc_#1_list_tl } { \tl_new:c { g_envc_#1_list_tl } }
    \tl_gput_right:cn { g_envc_#1_list_tl } { #2 }
    \exp_args:Nc \newcommand { w envc_#1_\cs_to_str:N #2 }
}
\NewDocumentCommand{\checkenvcommands}{ }
{
    \tl_if_exist:cT { g_envc_\use:c {@currenvir} _list_tl }
    {
        \tl_map_inline:cn { g_envc_\use:c {@currenvir} _list_tl }
        {
            \cs_set_eq:Nc ##1 { envc_\use:c {@currenvir} _\cs_to_str:N ##1 }
        }
    }
}
\ExplSyntaxOff

With \exp_args:Nc, TeX will jump over the next token and make a control sequence name out of the tokens in the following braced group, which is the higher level expl3 counterpart of

\expandafter\newcommand\csname <tokens>\endcsname

in “old style” programming.

Note also \tl_if_exist:cF instead of \cs_if_exist:cF. You're checking a variable, not a function.