Re: Trying to understand this ctxlua error

[Wolfgang Schuster <wolfgang.schuster.lists@gmail.com>]

Gerben Wierda schrieb am 06.04.2020 um 00:41:
> I got this error after I had changed some lua code:
> 
> tex error       > tex error on line 272 in file archimate-lua.new: ! 
> Undefined control sequence
> 
>          warnIfVerbose( "Breaking off the processing of node %s\nNo
>        l...eak                                                          
>            xsi:type", node)
> \luat_start_lua_code_indeed ...ormalexpanded {\endgroup \noexpand 
> \directlua {#1
>                                                                          
>          }}
> l.272 \stopluacode
> 
> 
> 
> <empty file>
> 
> 
> The control sequence at the end of the top line of your error message 
> was never
> \def'ed. You can just continue as I'll forget about whatever was undefined.
> 
> I have been looking at that code for over two hours, not seeing anything 
> wrong with it. But I’ve now finally found the culprit and I still do not 
> get it.
> 
> The culprit was:
> 
>            warnIfVerbose( "Breaking off the processing of %s\n No 
> elementRef", node)
> 
> The problem goes away when I use:
> 
>            warnIfVerbose( "Breaking off the processing of %s\nNo 
> elementRef", node)
> 
> (I don’t want the line after the node is printed to begin with a space).
> 
> But the lack of space between \n and N kills lua (apparently). For 
> completeness (as string.format and texio.write_nl are also in play):
> 
> function warnWithLabelIfVerbose( str, ... )
>    if verboseProgram then
>      texio.write_nl( str .. string.format(...))
>    end
> end
> 
> function warnIfVerbose( ... )
>    warnWithLabelIfVerbose("-----> ", ...)
> end
> 
> Is this a lua bug? A ConTeXt bug? Expected behaviour? And if so, why is 
> reported that on line 272 (where \stopluacode is) is the error? Or is 
> the error message indeed helpful and do I just lack the know how to 
> interpret it?

ConTeXt expands TeX commands in a luacode-environment
and when you have \n followed by text you create a new
command with starts with \n but since it isn't defined
you get a error message.

In the example below the commented block produces
the same error message as you get.

\starttext

%\startluacode
%print("text\ntext")
%\stopluacode

\startluacode
print("text\n text")
\stopluacode

\stoptext

Wolfgang
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