I received a very confusing error from Mojo::JSON while my app was trying
to parse a newly added config file using JSONConfig. While I have figured
it out, it raises a point worth mentioning, and possibly improving.
The error message was
> Can't load application from file "/home/ubuntu/Origin/bin/origin": Can't
> parse config "/home/ubuntu/Origin/origin.json": Malformed JSON: Expected
> string while parsing object at line 6, offset 24 at
> /home/ubuntu/perl5/perlbrew/perls/perl-5.20.0/lib/site_perl/5.20.0/Mojolicious/Plugin/JSONConfig.pm
>
> line 10.
>
So, there's a problem on line 6, character 24. But, here's what the config
file was:
origin.json:
1 {
2 "databases": {
3 "MODAPS": "Foo",
4 "ACPS" : "Bar"
5 },
6 %#Server secret, should be unique to each config.
7 %#See http://mojolicious.org/perldoc/Mojolicious#secrets
8 "secrets": "<%= $app->moniker %>",
9 }
Line 6, character 24 is the 'o' in 'should' on a comment line. What? Even
if I suppose it's disregarding comment lines, the 'p' in 'app' still looks
OK. What's more, changing line 8, even to a static string of the moniker,
still had no effect.
I finally modified Mojo::JSON::_throw, to have it show me the actual error
context as follows:
sub _throw {
# Leading whitespace
/\G[\x20\x09\x0a\x0d]*/gc;
# Context
my $context = 'Malformed JSON: ' . shift;
if (m/\G\z/gc) { $context .= ' before end of data' }
else {
my @lines = split "\n", substr($_, 0, pos);
my $popped;
$context .= ' at line ' . @lines . ', offset ' . length($popped = pop
@lines || '') . $popped;
}
die "$context\n";
}
This now gave me the error
> Can't load application from file "/home/ubuntu/Origin/bin/origin": Can't
> parse config "/home/ubuntu/Origin/origin.json
> ": Malformed JSON: Expected string while parsing object at line 6, offset
> 24 "secrets": "origin", at
> /home/ubuntu/perl5/perlbrew/perls/perl-5.20.0/lib/site_perl/5.20.0/Mo
> jolicious/Plugin/JSONConfig.pm line 10.
>
At this point it became clear the issue was the trailing comma on line 8 of
the config file that I'd completely overlooked.
Sri, et al, I'd like to suggest adding in the actual contextual line in
_throw, similar to my quick hack, to help clarify exactly where a parsing
error is coming from when comments and embedded perl are in play in the
.json.
Best,
-Randall
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