How to Determine the Current File Name and Line Number in the ConTeXt Source?

From: Tad Ashlock <taashlo@cyberdude.com>
To: ntg-context@ntg.nl
Subject: How to Determine the Current File Name and Line Number in the ConTeXt Source?
Date: Wed, 01 Jul 2009 05:01:10 -0600	[thread overview]
Message-ID: <4A4B41F6.2040005@cyberdude.com> (raw)

Is there a convenient way within a Lua block to determine the current 
file name and line number of the source file being processed by ConTeXt?

For example: (test.tex)
---------------------------------
\def\ShowLineNumber{%
    \ctxlua{print('current line number:', tex.current_line_number())
               print('current file:', tex.current_file_name())}}
\starttext
a line
\ShowLineNumber
another line

\ShowLineNumber
\stoptext
---------------------------------

With the following displayed:
---------------------------------
current line number: 6
current file: test.tex
current line number: 9
current file: test.tex
---------------------------------

I've considered hooking into the open_read_file callback and tracking 
the file name and line number (via reader) myself.  But that seems a bit 
heavy handed if the file name and line number information are available 
more directly.  And since that information is needed for error 
reporting, I'm thinking there's a good chance it is accessible.

(Just in case you're interested, the purpose of this is to be able to 
assemble code segments during the ConTeXt processing into external files 
with #line directives ala the C preprocessor.  That way if the 
subsequent compilation of the external file results in an error, the 
error message can refer back to the line of code in the ConTeXt source 
file.  This is part of the literate programming module that Kevin 
Robbins has been describing in another thread.)

Thanks,
Tad
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