Error with equaltiy comparisions with Fraction context after changing context

[somiaj]

Consider the following example problem.

DOCUMENT();
loadMacros(qw(PGstandard.pl contextFraction.pl PGML.pl));

Context('Fraction')->variables->are(c => 'Real');
$x = Formula("4c");
Context('Numeric');
$test = $x == 0 ? 'Yes' : 'No';
TEXT($test);
ENDDOCUMENT();

This problem produces the following error on 2.20.

ERRORS from evaluating PG file:
Can't call method "can" on an undefined value at line 395 of [PG]/macros/contexts/contextExtensions.pl
   from within context::Extensions::Super::super called at line 784 of [PG]/macros/contexts/contextFraction.pl
   from within context::Fraction::Parser::Number::new called at line 629 of [PG]/lib/Parser.pm
   from within Parser::Num called at line 159 of [PG]/lib/Parser.pm
   from within Parser::parse called at line 54 of [PG]/lib/Parser.pm
   from within Parser::new called at line 19 of [PG]/lib/Value/Formula.pm
   from within Value::Formula::new called at line 173 of [PG]/lib/Value/Formula.pm
   from within Value::Formula::compare called at line 851 of [PG]/lib/Value.pm
   from within Value::binOp called at line 865 of [PG]/lib/Value.pm
   from within Value::_compare called at line 7 of undefined

Removing the Context('Numeric') line causes the problem to work correctly. I caught this in a problem in which I changed the context to Matrix, so it seems the issue arises when changing the current context.

[somiaj]

I think I can fix my problem by extending the Matrix context to work with fractions correctly, but this might be a more general problem that might need fixed.

[dpvc]

OK, I tracked this down. The $x == 0 requires turning 0 into a Formula object, and it should be use the context that $x was created in to do that. It turns out that the Fraction context's replacement for Parser::Number (which is what the 0 will produce) doesn't properly pass on the needed context when it calls Parser::Number, so it creates the number in the current context (Numeric in this case) rather than the Fraction context. That leads to context::Extensions::Super::super not finding the needed data about the extension, since it is stored in the Fraction context, not the Numeric one.

The fix is not hard. Replace

pg/macros/contexts/contextFraction.pl

Line 784 in c86400b

my $num = &{ $self->super('new') }($self, @_);

with

       my $num  = &{ $self->super('new', $_[0]->context) }($self, @_);

and that should do it.

[somiaj]

@dpvc thanks, that did the trick and I'll make a PR.

[somiaj]

Fixed in #1338.