Investigate a non-class-based version

[simonw]

I'm thinking about using this with Datasette plugins, which aren't well suited to the current class-based mechanism because plugins may want to register their own additional dependency injection functions.

[simonw]

This would need to have a separate registry object. Here's a potential design:

# Register three functions
registry = AsyncRegistry(func1, func2, func3)
# Add another function later on
registry.register(func4)
# Resolve the result:
result = await registry.resolve(func1, arg=x)

That .resolve() method could accept either a function that has already been registered OR a string function name.

[simonw]

Since functions are no longer being directly coupled to one particular registry (in their class) I could skip the bit where the method itself is rewritten by the decorator to work magically. That's actually potential usability improvement since it's less surprising.

[simonw]

Initial rough prototype:

from functools import wraps
import inspect
import graphlib
import asyncio

class AsyncRegistry:
    def __init__(self, *fns):
        self._registry = {}
        self._graph = None
        for fn in fns:
            self.register(fn)
    
    def register(self, fn):
        self._registry[fn.__name__] = fn
        # Clear _graph cache:
        self._graph = None
    
    @property
    def graph(self):
        if self._graph is None:
            self._graph = {
                key: {
                    p
                    for p in inspect.signature(fn).parameters.keys()
                    if not p.startswith("_")
                }
                for key, fn in self._registry.items()
            }
        return self._graph

    async def resolve(self, fn):
        try:
            name = fn.__name__
        except AttributeError:
            name = fn
        return (await self.resolve_multi([name]))[name]
    
    async def resolve_multi(self, names, results=None):
        if results is None:
            results = {}

        # Come up with an execution plan, just for these nodes
        ts = graphlib.TopologicalSorter()
        to_do = set(names)
        done = set()
        while to_do:
            item = to_do.pop()
            dependencies = self.graph.get(item) or set()
            ts.add(item, *dependencies)
            done.add(item)
            # Add any not-done dependencies to the queue
            to_do.update({k for k in dependencies if k not in done})

        ts.prepare()
        plan = []
        while ts.is_active():
            node_group = ts.get_ready()
            plan.append(node_group)
            ts.done(*node_group)

        #instance._log(
        #    "Resolving {} in {}>".format(names, repr(instance).split(" object at ")[0])
        #)

        for node_group in plan:
            awaitable_names = [name for name in node_group if name in self._registry]
            # instance._log("  Run {}".format(awaitable_names))
            awaitables = [
                self._registry[name](
                    **{k: v for k, v in results.items() if k in self.graph[name]},
                )
                for name in awaitable_names
            ]
            awaitable_results = await asyncio.gather(*awaitables)
            results.update(dict(zip(awaitable_names, awaitable_results)))

        print("results:", results)
        return results

    
def _make_fn(fn, registry):
    parameters = inspect.signature(fn).parameters

    @wraps(fn)
    async def inner(**kwargs):
        # Any parameters not provided by kwargs are resolved from registry
        to_resolve = [
            p
            for p in parameters
            # Not already provided
            if p not in kwargs
            # Doesn't have a default value
            and parameters[p].default is inspect._empty
        ]
        missing = [p for p in to_resolve if p not in registry]
        assert (
            not missing
        ), "The following DI parameters could not be found in the registry: {}".format(
            missing
        )

        results = {}
        results.update(kwargs)
        if to_resolve:
            resolved_parameters = await resolve(registry, to_resolve, results)
            results.update(resolved_parameters)
        return await method(
            self, **{k: v for k, v in results.items() if k in parameters}
        )

    return inner

[simonw]

Got this working in a branch. Updated documentation is here: https://github.com/simonw/asyncinject/blob/ed8fbbdef513ff8385f91cc345226439deab6515/README.md