CQRS Api Platform

/!\ WIP /!\

Maybe that one day this could be a bundle... Ideas from https://github.com/api-platform/core/issues/2729

Notes

This is an attempt to add CQRS on top of Api Platform.

It's using the symfony messenger component with two buses:

• QueryBus
• CommandBus (todo)

And removing most of the api platform's listeners by transforming them in middlewares.

Event listeners in api.xml (api-platform/core dependency) should be changed:

        <service id="api_platform.listener.request.read" class="App\EventListener\ReadListener">
            <argument type="service" id="App\Query\QueryBusInterface" />
            <argument type="service" id="api_platform.serializer.context_builder" />
            <argument type="service" id="api_platform.identifier.converter" />

            <tag name="kernel.event_listener" event="kernel.request" method="onKernelRequest" priority="4" />
        </service>

        <!-- this is TBD -->
        <service id="api_platform.listener.view.write" class="App\EventListener\WriteListener">
            <argument type="service" id="api_platform.data_persister" />
            <argument type="service" id="api_platform.iri_converter" on-invalid="null" />
            <argument type="service" id="api_platform.metadata.resource.metadata_factory" on-invalid="null" />

            <tag name="kernel.event_listener" event="kernel.view" method="onKernelView" priority="32" />
        </service>

In validator.xml for now:

        <service id="api_platform.listener.view.validate" class="App\EventListener\NoopListener">
            <argument type="service" id="api_platform.validator" />
            <argument type="service" id="api_platform.metadata.resource.metadata_factory" />

            <tag name="kernel.event_listener" event="kernel.view" method="onKernelView" priority="64" />
        </service>

        <service id="api_platform.listener.view.validate_query_parameters" class="App\EventListener\NoopListener" public="false">
            <argument type="service" id="api_platform.metadata.resource.metadata_factory" />
            <argument type="service" id="api_platform.filter_locator" />

            <tag name="kernel.event_listener" event="kernel.request" method="onKernelRequest" priority="16" />
        </service>

Todo:

• add context for data providers in the query
• support write through commands
• transform validator listeners as middlewares
• Maybe even remove the Serialize/Deserialize Listeners?
• Inputs should be dispatched as Queries/Commands
• For graphql there could be a Query and a Mutation bus
• do a compiler pass to remove api platform listeners
• transform into a bundle
• share