# [NTG-context] Trying to understand this ctxlua error

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?

G

(Took me three hours, this one. Just removing that space that happened with
some other changes was the culprit. Totally unexpected for me.)
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