Use svcs to fill in arguments of a function call or a type (unregistered) instantiation.

[jbasko]

Can I use svcs to inject dependencies in callables based on annotations as I am trying to in the following example:

import pytest
import svcs


@pytest.fixture()
def registry():
    return svcs.Registry()


@pytest.fixture()
def container(registry):
    return svcs.Container(registry=registry)


def test_can_call_function_with_deps_injected(registry, container):
    def doubles_int(x: int):
        return x * 2

    registry.register_value(int, 5)
    assert container.get(doubles_int)() == 10

Similarly, when I create an instance of an unregistered type which depends on some registered stuff, from a DI framework I would expect a utility which injects it so that I don't have to explicitly request them from the container. Is there a thing like that in svcs?

[hynek]

Are you asking for some kind of container.call_and_inject(f) that introspects the signature of f and then, according to their types presumably, runs the appropriate container.get() and passes the results as arguments?

[jbasko]

Yes, exactly. But now I've read a bit more, I see that you recommend incant for that.

[hynek]

True, it might be a fun exercise to implement it on top of svcs tho. I think @Tinche even did it once.

[hynek]

I think #94 might be an interesting compromise?

[jbasko]

Kind of, it could be a usable building block. Thanks.

I would not want to register every function, and also I would expect that this does not cache the results (so, not singletons), and that it does not expect all arguments to be injectables (instead, some can be passed at the time when one calls inspect_and_get). I was after inspect_and_call, but I would expect something like inspect_and_get to be available as well.