[xsl] XSLT 2.0: Saxon et. al.: Tracking XML source line numbers

[Justin Johansson <procode@xxxxxxxxxx>]

Hello all,

My last question for today, and thanks to all for your patience with, and
responses to, this newcomer to your list.

Saxon has an XSLT extension function saxon:line-number($node) which returns
the line number associated with a node in the XML source tree (though you
need to use the -l option to enable line number tracking and perhaps other
XSLT processors have a similar such function.  However, is there any way
that one can achieve the same functionality as C's #line directive with an
XSLT processor, even if it an XSLT extension, and tell the processor that
line and file numbers for errors and warning associated with particular
source node actually relate to another place earlier in chain of pipeline
XML/XSLT processing.

The background and rationale for this question is as follows:

C and C++ preprocessors have long had the ability for the programmer to
modify the file name and line numbers for which the compiler outputs errors
and warnings associated with source code.

Quoting Visual Studio C++ help
<quote>
The #line directive lets you modify the line numbers and, optionally, the
file name in the compiler output for errors and warnings. 
#line [ number ["file_name"] | hidden | default ]
</quote>

Apparently some other languages, e.g. Perl, have a similar facility but
what about XSLT?

A use case is the YACC processor from the C world.  This processor takes as
input a BNF-like description of the grammar for particular language, say,
cplusplus.y, and produces as output a file, cplusplus.c, which contains C
source code for constructing a parser for the given language.  When a
warning or error occurs in compiling cplusplus.c, the C compiler associates
the same with a line number in cplusplus.y instead of cplusplus.c.

It would be useful to achieve a similar thing in XSLT to make the debugging
of automatically generated stylesheets easier.

In response to my post on Jeni Tennison's blog re auto generating XSLT
stylesheets,

	http://www.jenitennison.com/blog/node/13#comments ,

Jeni rightfully pointed out the problem of debugging such auto generated
stylesheets.

	http://www.jenitennison.com/blog/node/13#comment-4040

Thanks to all in advance for the tips and tricks,


Justin Johansson
Freelance XML / XSLT / XQuery Developer
Australia

procode(at)tpg(dot)com(dot)au