This is follow up to:

• PR [DI] Reference tagged services in config
• post New in Symfony 3.4: Simpler injection of tagged services

It is the same, just instead of tags, it uses directly types.

Let's say we have 2 classes:

• ResolverCollector - one services
• SingleResolverInterface - many services

We want to collect all services of SingleResolverInterface and pass them to ResolverCollector (ctor or via method is not relevant).

The similar way Commands to Console\Application, but for own class and without tags.

Right now we have to create CollectorCompilerPass similar to this:

final class CollectorCompilerPass implements CompilerPassInterface
{
    public function process(ContainerBuilder $containerBuilder): void
    {
        $collectorDefinition = $containerBuilder->get(ResolverCollector::class);

        foreach ($containerBuilder->getDefinitions() as $name => $definition) {
            if (! is_a($definition->getClass(), SingleResolverInterface::class, true)) {
                 continue;
            }

            $collectorDefinition->addMethodCall('addSingleResolver', [new Reference($name)]);
        }
    }
}

Negatives

• bundle must exists
• or must be registered in Kernel with interface
• it's not right in config, kind of hidden configuration
• requires split configuration in PHP

Desired state

• config only
• 1 place to setup to collect services from container x not just current one like _defaults and instanceof does
• not 2 places: config + PHP (Kernel, CompilerPass or Extension)

From Bundle to Config

Since Symfony 3.4/4.0 goes more and more bundle-less and moves to config:

services:
    ResolverCollector:
        calls:        
            - ['addSingleResolvers', [!tagged single_resolver]]

This would the best solution then:

services:
    ResolverCollector:
        calls:
            - ['addSingleResolvers', [!typed SingleResolverInterface]]

How to achieve that? Could similar code from [DI] Reference tagged services in config PR work?