[Dbix-class] Maybe a Regression? Without a primary key, prefetches fail.

[J. Shirley]

I'm not sure if this counts as a regression, but it was for me :)

I have a class which is defined as:

package MyApp::Schema::StupidJoinTable;

use strict;
use warnings;

use base 'DBIx::Class';

__PACKAGE__->load_components("Core");

__PACKAGE__->table("stupid_join_table");
__PACKAGE__->add_columns(
    "stupid_id",
    {
        data_type       => "integer",
        default_value   => undef,
        is_nullable     => 0,
        size            => 11
    },
    "stupider_id",
    {
        data_type       => "integer",
        default_value   => undef,
        is_nullable     => 0,
        size            => 11
    },
);

__PACKAGE__->belongs_to( 'thing_1', 'MyApp::Schema::Thing', 'stupid_id');
__PACKAGE__->belongs_to( 'thing_2', 'MyApp::Schema::Thing2', 'stupider_id');

1;


Now, if I attempt to prefetch this relationship, I get this error
thrown (from DBIx/Class/Row.pm, line 1138):
      $class->throw_exception("Implicit prefetch (via select/columns)
not supported with accessor 'multi'");

The reason is that without ->set_primary_key(...) in this result
definition, the query on type is an empty array.

So, $prefetch->{$pre} is simply an empty array (the line "if (ref
$prefetch->{$pre}[0] eq 'ARRAY')").


This behavior is not changed if I explicitly define the columns on the
relationships (eg., { 'foreign.stupid_id' => 'self.stupid_id' })

I'm still running 0.08115 in production, so it is working there, but
this came up on my tests as a failure.  The fix for me is just adding
in the primary keys as they should be, but it seemed like an odd
behavior.

If it's a bug, I'm happy to at least commit a failing test case :)

Thanks,
-Jay