Allow to add drivers to a driver chain

[bakura10]

In my specific case, each driver needs to have a reference to the metadata factory, and to create the metadata factory I need... the driver chain. So I'm stuck. Adding this method add a bit of flexibility to the DriverChain.

[bakura10]

Thanks, tell me when you tag :).

[schmittjoh]

Hm yeah, we don't have terribly many changes yet :)

btw, I'm thinking about whether it would make sense to add a MetadataFactoryAware interface so that the factory injects itself into drivers if necessary. This would stream-line the construction of the objects.

However, before we would do that I'd like to learn a bit more why you inject the metadata factory. I presume you want to recursively load metadata?

[bakura10]

Exactly. I may have multiple drivers, and when a driver create an object it may needs to get the data from the factory and merge data.

[schmittjoh]

Ah, I see. Is the code open-source, so that I could take a look at it?

[bakura10]

Yes it is.

The driver: https://github.com/zf-fr/zfr-rest/blob/voltaire/src/ZfrRest/Resource/Metadata/Driver/AnnotationDriver.php#L65

And the factory used to create it: https://github.com/zf-fr/zfr-rest/blob/voltaire/src/ZfrRest/Factory/ResourceMetadataFactoryFactory.php#L55

[bakura10]

Hi @schmittjoh ,

After implementing my custom factory, I encounter an annoying problem, and I have no idea about how to solve it. I have a nice circular dependency problem here: https://github.com/zf-fr/zfr-rest/blob/voltaire/src/ZfrRest/Resource/Metadata/Driver/AnnotationDriver.php#L109

Basically, this happens when using a bi-directional associations between two resources. I load the resource metadata for resource A, that loads metadata for resource B, which itself loads metadata for resource A and... problem!

I can't avoid the bi-directional here, because mapping can be overridden by an association. Do you have any idea about how I could solve this issue?

[schmittjoh]

What result would you expect? Do you have an example where I can see where this metadata is coming from, i.e. the annotated objects?

[bakura10]

Yes, annotated objects.

I have made a simple failing tests:

• Entity A: https://github.com/zf-fr/zfr-rest/blob/voltaire/tests/ZfrRestTest/Resource/Metadata/Driver/AnnotationAsset/CircularA.php
• Entity B: https://github.com/zf-fr/zfr-rest/blob/voltaire/tests/ZfrRestTest/Resource/Metadata/Driver/AnnotationAsset/CircularB.php

and the failing test: https://github.com/zf-fr/zfr-rest/blob/voltaire/tests/ZfrRestTest/Resource/Metadata/Driver/AnnotationDriverFunctionalTest.php#L103

Basically, when there is an association, the mapping defines on the association must override mappins define globally on the associated resource. Not sure if it makes sense :o.

[schmittjoh]

What I could think of is that you defer the resolution of that metadata. Basically, instead of trying to load the metadata right away in the driver, you would simply add a note to the class metadata that an association still needs to be resolved.

Then, you could wrap the MetadataFactory with your own implementation which would check all loaded metadata whether they contain associations which need to be resolved, and resolve them then. I think this would also be a cleaner implementation as the resolution would not have to be implemented in each driver (if you for example have an annotation driver, a yaml driver, etc.).

Would that work?

[bakura10]

The custom metadata factory seems the best solution! I'll try that :).

[bakura10]

Haaa this is not currently possible because MetadataFactory is final :/. I'm going to make a PR.