Bug #92818 for Moose: Misleading error "class name X does not match class->name Y"

Fri Feb 07 13:33:15 2014 POPEL [...] cpan.org - Ticket created

Subject:

Misleading error "class name X does not match class->name Y"

The real cause of the error is a missing required attribute. In a simple case, Moose outputs a reasonable error message: $ perl -e 'package C1; use Moose; has x => (is=>qw(rw),required=>1); package main; my $obj=C1->new' Attribute (x) is required at [...]/Moose/Exception.pm line 38 [...] However, in a slightly more complicated case, Moose outputs a completely misleading error: $ perl -e 'package C1; use Moose; has x => (is=>qw(rw),required=>1); package C2; use Moose; extends "C1"; package main; my $obj=C2->new' class_name (C2) does not match class->name (C1) at [...]/Moose/Exception.pm line 38 [...] Debugging such a message is really annoying (esp. if you just get the error traceback from a user without having access to his computer). I think it is a regression, but I am not able now to install an older Moose to check it. BTW: is there some trick how to do this (e.g. with perlbrew & backpan)?

Fri Feb 07 13:59:45 2014 ether [...] cpan.org - Correspondence added

Didn't you already file this as https://rt.cpan.org/Ticket/Display.html?id=92770 ? You didn't report what Moose version you were using, but I think if you try with 2.1204 you will find things significantly improved.

Fri Feb 07 13:59:46 2014 The RT System itself - Status changed from 'new' to 'open'

Fri Feb 07 16:14:52 2014 POPEL [...] cpan.org - Correspondence added

On Fri Feb 07 13:59:45 2014, ETHER wrote: Show quoted text

> Didn't you already file this as > https://rt.cpan.org/Ticket/Display.html?id=92770 ?

No, that was another problem which is solved now (thanks). however, this problem is still here in Moose 2.1204. Just try it perl -e 'package C1; use Moose; has x => (is=>qw(rw),required=>1); package C2; use Moose; extends "C1"; package main; my $obj=C2->new' The expected error message is "Attribute (x) is required". The current error message is "class_name (C2) does not match class->name (C1)", which makes no sense to me. Show quoted text

> You didn't report what Moose version you were using,

I filled "Broken in"=2.1204. (I know it is broken also in some previous versions. I updated to the newest version of Moose before reporting this problem.) Martin Popel

Sat Feb 08 13:04:42 2014 ether [...] cpan.org - Correspondence added

The 'AttributeIsRequired' error is there, but it's farther down in the stack trace, because the exception heirarchy itself runs into problems and then generates a 'ClassNamesDoNotMatch' exception on itself. The stack trace is correct in 2.1005. The second exception is at line 80 of Moose::Exception::AttributeIsRequired: if( $self->has_attribute_name && $self->has_attribute && ( $self->attribute->name ne $self->attribute_name ) ) { throw_exception( AttributeNamesDoNotMatch => attribute_name => $self->attribute_name, attribute => $self->attribute ); It looks like there's a bug lurking here in the exception system; digging further...

Sat Feb 08 15:22:35 2014 ether [...] cpan.org - Correspondence added

Actually it's the "class names do not match" exception that we're hitting in lib/Moose/Exception/AttributeIsRequired.pm -- because the attribute actually lives on C1, but we encountered the problem when dealing with C2. The problem is this code: sub _build_class { my $self = shift; if( $self->has_attribute ) { return $self->attribute->associated_class; } elsif( $self->is_class_name_set ) { return Class::MOP::class_of( $self->class_name ); } }; In this case, we're lifting the class name off of the attribute (C1) and comparing it to the class name of the instance (C2), then complaining that they don't match. I don't think this is the right thing to do - in the exception, we should always refer to the class name of the instance, not the class name where the attribute originated (unless we use *both* of them in the error message, which we don't). Cabal, what say ye?

Wed May 14 10:32:55 2014 ether [...] cpan.org - Correspondence added

This is fixed in 2.1206, being released today.

Wed May 14 10:32:57 2014 ether [...] cpan.org - Status changed from 'open' to 'resolved'

Wed May 14 20:51:54 2014 ether [...] cpan.org - Fixed in 2.1206 added