[Feature Request] Get a registered dependency outside of route handlers as well

[guacs]

Is your feature request related to a problem? Please describe your use case.
I am trying to access a service that I have registered as a dependency in an event handler to a custom signal.

class MyService:
    
    def __init__(self, connection: DBConnection):
        self._connection = connection

@app.signal("some.dummy.event")
def dummy_event_handler(**context):
    app = Sanic.get_app("my-app")
    request = Request.get_current()
   
    dependency_callable = app.ext._injection_registry.get(dependency_type)
    # I'm not sure what the impact of using this request object is.
    # What if I'm calling this after the request that dispatched this event
    # has already been processed and the response was sent?
    service = await dependency_callable(request)
    ...

Describe the solution you'd like
It would be nice to get an API which takes in a type and attempts to get the dependency from the registry.

class MyService:
    ...

@app.signal("some.dummy.event")
def dummy_event_handler(**context):
    service = Sanic.get_app("my-app").ext.get_dependency(MyService)
    # do something with the service

[BDadmehr0]

Certainly! Here's an example of an API that takes a type and attempts to retrieve the corresponding dependency from the registry:

class DependencyRegistry:
    def __init__(self):
        self._registry = {}

    def register_dependency(self, dependency_type, dependency):
        self._registry[dependency_type] = dependency

    def get_dependency(self, dependency_type):
        return self._registry.get(dependency_type)


class MyService:
    def __init__(self, connection: DBConnection):
        self._connection = connection


app = Sanic("my-app")
registry = DependencyRegistry()


@app.route("/dependency/<dependency_type>")
async def get_dependency(request, dependency_type):
    dependency = registry.get_dependency(dependency_type)
    if dependency is None:
        return json({"error": "Dependency not found"}, status=404)
    return json({"dependency": str(dependency)})


@app.listener("before_server_start")
async def setup_registry(app, loop):
    # Register dependencies in the registry
    registry.register_dependency(DBConnection, "database_connection")


if __name__ == "__main__":
    app.run(host="0.0.0.0", port=8000)

In this example, we have a DependencyRegistry class that maintains a dictionary _registry for storing dependencies. It provides methods to register and retrieve dependencies.

The MyService class is just a placeholder representing a class that requires dependencies.

The Sanic app (app) is created with the name "my-app". We define a route /dependency/<dependency_type> that accepts a dependency_type parameter. When a GET request is made to this route, the API attempts to retrieve the corresponding dependency from the registry based on the provided dependency_type. If the dependency is found, it is returned in the response. Otherwise, a 404 error response is returned.

In the before_server_start listener, we can register dependencies in the registry. In this example, we register a DBConnection dependency with the value "database_connection".

You can modify and expand this example to suit your specific needs.

[guacs]

I'm sorry @BDadmehr0 , but I don't think your proposed solution is what I'm looking for. When I said API, I wasn't talking about an HTTP endpoint but in the more general sense. Also your DependencyRegistry doesn't handle resolving the dependencies required by the dependency I'm trying to get.

[BDadmehr0]

Sorry, but I can't think of any other solution