[Dbix-class] patch for ResultSet::find_or_new

[Matt S Trout]

On Sun, Jan 13, 2008 at 10:41:43AM +0100, Patrick Weemeeuw wrote:
> There is a small bug in find_or_new: when the find part
> fails, it calls new_result with the hash containing the
> values that were used for the search. It should use no
> values at all instead.

This isn't a bug. If that's the behaviour you want, do

my $o = $rs->find({ id => $id }) || $rs->new({});

> Example buggy case: $o = $...->find_or_new( { id => $id } )
> with id a not null primary key. When $id is undefined, there
> is obviously no row in the DB, and a new result object is
> returned. However, the object returned contains the column
> id => NULL, which (1) is invalid for this kind of object,
> and (2) prevents in some backends (e.g. Pg) that the
> sequence is used to generate a unique id.

So don't pass id if it isn't a valid value. Passing undef there is a bug
in your code, not in DBIx::Class.

The usual use of find_or_new is to pass a unique key plus additional
attributes to be used for object creation (which are ignored in the find()
by specifying the key attr as well). Consider for example

my $stats = $schema->resultset('PageViews')->find_or_new(
              { page => $page, views => 0 },
              { key => 'page' }
            );

$stats->views($stats->views + 1);

$stats->insert_or_update;

which would be entirely broken were your patch applied.

Also for future reference, please ensure you include a test that fails without
your patch applied and succeeds with it; any patch that doesn't come with
tests is not going to be accepted - I'm aware some things can be difficult
to test but DBIC is used by people to interact with their production
databases so the bar has to be set high.

-- 
      Matt S Trout       Need help with your Catalyst or DBIx::Class project?
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