Since everyone deploys minified/combined wads of JS goo, debugging errors in the field can be a bitch. The idea behind sourcemaps is to provide a way for web developers to debug their code once deployed. Sourcemaps provide a compact index into the minified source that lets you map the file/line/col given to you in a JS runtime error thrown by your minified JS back into the real file/line/col in your source code.
A decent albeit dated tutorial can be found here: https://www.html5rocks.com/en/tutorials/developertools/sourcemaps/
The use case for this module is a server-side component in Perl that
receives JS runtime error information somehow from a web application's
JS front end. You generally have the source map available on the
server already but there is a discover function in JS::SourceMap
that will search JS code for a pointer to its source map as per
convention. You'll have to fetch the URL that discover finds
yourself, though.
This module is inspired by https://github.com/mattrobenolt/python-sourcemap It hews fairly closely to that implementation. I brought over all of the same test inputs (t/fixtures) and all of the tests that made sense (no iterators in Perl).
Module github repo: https://github.com/StAlphonsos/perl-sourcemap Feel free to open issues there if you find them. The module is also available on CPAN.
It's the usual deal:
$ perl Makefile.PL
$ make
$ make test
$ [ `uname` != OpenBSD ] && alias doas=sudo # doesn't everyone do this?
$ doas make install
Please read the JS::SourceMap POD, but in a nutshell:
#!/usr/bin/perl
# args: mapfile line col
# output: line col sourcefile
use JS::SourceMap;
$map = JS::SourceMap::load(shift(@ARGV)) or die "bad map";
$token = $map->lookup(@ARGV) or die "line/col out of bounds";
print sprintf("%d %d %s\n",$token->src_line,$token->src_col,$token->src);
The web is a scary place. Enjoy.