Ping dependencies

[Tishka17]

Add separate decorator to provide ping functionality. It has no scope during declaration and can be used to run specific code declated in providers:

Declaration:

class Provider:
   @ping
   def foo(self) -> None:
         print("PING")
   @ping
   def bar(self, session: Session) -> None:
         session.execute(select(1))
         print("PING SESSION")

Usage:

container.ping()

That call will find all pings declared with current and parent scopes and request them

Discuss: should we unify this technic?

[Tishka17]

Discuss: auto calculation of scope based on dependencies vs explicit scope

[Forceres]

Discuss: auto calculation of scope based on dependencies vs explicit scope

Good discussion point, there is a boundary between code readability and developer experience. Auto calculation can be good convenient option (NestJS DI System has it), but it can be difficult to read dependency source from a lot of nested providers (modules)

[tuukkamustonen]

The description proposes API where you explicitly declare each ping. That's the most compatible way, certainly.

It could be nice if there was some introspection in play, too. Like if a dependency defines ping (or alike) method with certain arguments/annotations then it would be automatically registered/called.

class SomeClass:
    def ping(self):
         ...

Then you wouldn't have to explicitly define the ping each time.

Or @provide(ping=True) or @provide(ping="custom_method_name") though that would be bad for type safety.

Though, I don't think many dependencies need to define pings. Most likely just IO (database, cache, connections to other HTTP servers, etc). And in those cases you normally need to manually define/customize how the ping is done, anyway.

So, the proposed API would most likely suffice.