On Sat, Dec 14, 2019 at 10:31:20PM +0100, Hans Hagen wrote:
> On 12/14/2019 5:43 PM, Rudolf Bahr wrote:
> > 
> > Hello All,
> > 
> > In:
> > LuaMetaTeX, Version 2.03.3
> > ConTeXt  ver: 2019.12.12 19:35 MKIV beta  fmt: 2019.12.12  int: english/english
> > I get the following error message:
> > 
> > tex error       > error not related to input file:
> > tex error       >   tex: ! Emergency stop
> > tex error       >   lua: ?
> > tex error       >   mps: -
> >
> > In LuaTeX ... I get a "*" instead of the error message above.
> > And again my program does all what it should, but a grey pdf-page too.
> >
> > Sorry, no MWE available.


On Sat, Dec 14, 2019 at 07:27:34PM +0100, Otared Kavian wrote:
> 
> Since I have also suffered somewhat from the cryptic (and often useless…) error messages, I understand your frustration :-)
> Now, maybe if you do 
> 	context --directives="system.showerror" myfile.tex
> then you get a file named « myfile-status.html » which is more helpful.


On Sat, Dec 14, 2019 at 10:31:20PM +0100, Hans Hagen wrote:
>
> normally an * means: waiting for input .... and no message is then involved
> as in principle there is no real error, apart from waiting for input


Otared and Hans, thank you for your answers and Otared especially for your
sympathy! :-)

In the meantime I could get rid of "! Emergency stop" and "*" by changing
a \def-command which calls a luacode subprogram; see further down in my MWE.

My program run now looks essentially better, but "--directives="system.showerror" 
and "<my program>-status.html" still report an error: "! Undefined control sequence"
without telling which control sequence is undefined. How reliable is this error
message? I don't know of control sequences in luacode or what does this error message
mean?

Here is a MWE which shows my program structure. Sorry, this MWE works really :-)
During my attempts to find the error I got for a short time the message: "Invalid
\starttext ... \stoptext structure" which I don't understand.

--------------------------------------------------- MWE -------------------------------
\def\projectpath{/home/sam/trip-2019/}

\startluacode
   userdata = userdata or {}
   u = userdata

   function u.table_save ( tab, file )
      local tab   = tab
      local file  = file

      dofile ("table_save_u_table_load.lua")
      table.save(tab, file)
   end


   function u.Init ( col )

      local col  = col 
      local ppth = tokens.getters.macro("projectpath")
      local xO   = tokens.getters.macro("xO")
      local yO   = tokens.getters.macro("yO")

      local I = {}	-- Table of initial values
      I ["projectpath"] = ppth
      I ["column"]      = {}
      I ["column"][col] = {}
      I ["column"][col]["layerpos"] = {}
      I ["column"][col]["layerpos"] ["xO"] = xO
      I ["column"][col]["layerpos"] ["yO"] = yO

      u.table_save(I,"I-Table.lua") 
   end
   
\stopluacode

%\def\Init #1 {\ctxlua {u.Init ([==[#1]==]) }}% --the blanks produced my "! Emergency stop"
\def\Init#1{\ctxlua{u.Init([==[#1]==])}}%       --in this form the command works 

\starttext
   \def\Column{A}%
   \def\xO{0}%  in pt
   \def\yO{20}% in pt

   \Init{\Column}%%
\stoptext
---------------------------------------------------------------------------------------
For those possibly interested in running this MWE I append "table_save_u_table_load.lua",
a lua program to save and reload lua tables, found in the lua homepage. Anyway, the
resulting flattened table "I" is here:

return {
-- Table: {1}
{
   ["column"]={2},
   ["projectpath"]="/home/sam/trip-2019/",
},
-- Table: {2}
{
   ["A"]={3},
},
-- Table: {3}
{
   ["layerpos"]={4},
},
-- Table: {4}
{
   ["yO"]="20",
   ["xO"]="0",
},
}



I think nobody will be able to help me in this case, I myself have to try again and 
again to finally find the error. If so, this would be the nicest christmas gift to me :-)

Best regards,

Rudolf