block module: item-outside-list error is not correctly setup

[u-fischer]

If one use an \item outside a list one get the error message

! Undefined control sequence.
<argument> \__block_item_instance:n 

If one define the command

\DocumentMetadata{testphase={block}}
\documentclass{article}
\begin{document}

\ExplSyntaxOn
\def\__block_item_instance:n{}
\ExplSyntaxOff

\item 

\end{document}

the message changes to

! LaTeX Error: Unknown message 'item-in-nonlist' for module '__block'.

[car222222]

That final message is very strangely worded!

But something like that should be the principal message.

[FrankMittelbach]

@car222222 It is not strangely worded, it is just not the message you expect seeing. The above LaTeX error says that some L3 layer message is not found (probably misnamed), it is not saying anything about \item in the wrong place.

[car222222]

Yes, OK. I see now why it looks strange. Maybe it is OK for what it is.

[u-fischer]

@FrankMittelbach I would suggest to change the test and message to

      \cs_if_free:NTF \@@_item_instance:n %%FMi?
        %{ \msg_error:nnn { @@ } { item-in-nonlist } { \item[{#1}] } }
        { 
          \@latex@error{Lonely~\string\item--perhaps~a~missing~
           list~environment}\@ehc
        }   

This would give the standard error:

! LaTeX Error: Lonely \item--perhaps a missing list environment.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              

l.181 \item x
             xx

OK?

[car222222]

That suggested message, whilst very amusing, is somewhat too vague . . . or not?

[u-fischer]

That is the standard message you get since 30 years or so. I simply copied it from latex.ltx.

[car222222]

OK with me!

[FrankMittelbach]

That suggested message, whilst very amusing, is somewhat too vague . . . or not?

actually you might be the one who invented it :-) or I or David at the time matching perhaps a missing \item with a smile

[davidcarlisle]

That suggested message, whilst very amusing, is somewhat too vague . . . or not?

actually you might be the one who invented it :-) or I or David at the time matching perhaps a missing \item with a smile

or Rainer:-)

% \changes{LaTeX2.09}{1991/11/04}
%         {(RmS) added default definition for \cs{makelabel},
%               to produce an error message.}

[FrankMittelbach]

or Rainer ... but we have all been guilty of agreeing to this message (and I still think it is a nice and matching one).

[car222222]

No guilt needed!