Silverstripe-framework: belongs_many_many when though list used for many_many

[priyashantha]

Affected Version

4.1.0

Description

Although developer guide says you can use $belongs_many_many relationship for many_many_through lists as you used to, it looks like you can't.

When I do it as in the documentation (adding/updating relation classes with FQNs) it always complaining "belongs_many_many relation {$parentClass}.{$component} points to {$specification} without matching many_many"

Steps to Reproduce

If you set up an example like in the documentation but update relation classes with FQNs then you'll simply notice this issue.

PRs:

• [ ] https://github.com/silverstripe/silverstripe-framework/pull/8140

[priyashantha]

Oops.. I just noticed that the fix is in the master branch when I was going to submit a PR. So it'd be pretty nice if we could get a release with this fix as latest release doesn't contain that update?

[dhensby]

@priyashantha do you have a link to the PR where the fix was added?

[priyashantha]

@dhensby Sorry. I don't know a link for a PR. I think you got me wrong. I just wanted to submit a PR as I was in 4.1.0. But when I come to the file https://github.com/silverstripe/silverstripe-framework/blob/master/src/ORM/DataObjectSchema.php#L1015 the fix was there. So no needed to add any PR.

[priyashantha]

@dhensby I think this is not an issue anymore. But it'd be awesome if we'd have a release with that fix soon :)

[dhensby]

OK - that line you linked to was introduce by https://github.com/silverstripe/silverstripe-framework/pull/7928 and that's been merged into 4 so will make the 4.2.0 release, whenever that is...

If there's an existing bug in 4.1 with this, it may be worth backporting

[priyashantha]

Yup. In latest 4.1.0 release the DataObjectSchema::getManyManyInverseRelationship() looks:

protected function getManyManyInverseRelationship($childClass, $parentClass)
    {
        $otherManyMany = Config::inst()->get($childClass, 'many_many', Config::UNINHERITED);
        if (!$otherManyMany) {
            return null;
        }
        foreach ($otherManyMany as $inverseComponentName => $nextClass) {
            if ($nextClass === $parentClass) {
                return $inverseComponentName;
            }
        }
        return null;
    }

which hasn't handle the through list.

[kinglozzer]

Looks like this was fixed as part of a new feature, but @tractorcow’s suggestion here sounds like it could be suitable for a patch release if it fixes the issue https://github.com/silverstripe/silverstripe-framework/issues/7911#issuecomment-370600840

[Valandur]

I'm not sure if this is related to this issue, if not I will open a new one.

In the docs it's stated that polymorphic many_many through relations are possible, but when trying the code sample (using SS 4.1.1) provided there I get the error

[Emergency] Uncaught InvalidArgumentException: many_many through relation SomeObject.Tags from references a polymorphic field TagMapping::Parent which is not supported

Do I have to enable this experimental feature somehow, or is this also something that's coming in 4.2.0?

[dhensby]

I think polymorphic many_many_through is in 4.x only (4.2) at the moment.

[tractorcow]

Yes we can backport the fix; It'll re-enable belongs_many_many with many_many_through in 4.1. As suggested we'll just port back this code https://github.com/silverstripe/silverstripe-framework/blob/master/src/ORM/DataObjectSchema.php#L1014-L1020

No we can't fix it for polymorphic belongs_many_many though; Its currently impossible without massive refactoring. Unidirectional many_many through should work with polymorphic fine however.

Polymorphic many_many through is 4.2 only.

I hope that helps :D

[priyashantha]

@tractorcow That's awesome news. If this issue could be updated after backport done that be awesome. Thanks.

[tractorcow]

Fix at https://github.com/silverstripe/silverstripe-framework/pull/8140

[kinglozzer]

Closed by https://github.com/silverstripe/silverstripe-framework/pull/8140#event-1665766660