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https://github.com/simonw/datasette/issues/878#issuecomment-970624197 https://api.github.com/repos/simonw/datasette/issues/878 970624197 IC_kwDOBm6k_c452ozF 9599 2021-11-16T19:49:05Z 2021-11-16T19:49:05Z OWNER Here's the latest version of my weird dependency injection async class: ```python import inspect class AsyncMeta(type): def __new__(cls, name, bases, attrs): # Decorate any items that are 'async def' methods _registry = {} new_attrs = {"_registry": _registry} for key, value in attrs.items(): if inspect.iscoroutinefunction(value) and not value.__name__ == "resolve": new_attrs[key] = make_method(value) _registry[key] = new_attrs[key] else: new_attrs[key] = value # Topological sort of _registry by parameter dependencies graph = { key: { p for p in inspect.signature(method).parameters.keys() if p != "self" and not p.startswith("_") } for key, method in _registry.items() } new_attrs["_graph"] = graph return super().__new__(cls, name, bases, new_attrs) def make_method(method): @wraps(method) async def inner(self, **kwargs): parameters = inspect.signature(method).parameters.keys() # Any parameters not provided by kwargs are resolved from registry to_resolve = [p for p in parameters if p not in kwargs and p != "self"] missing = [p for p in to_resolve if p not in self._registry] assert ( not missing ), "The following DI parameters could not be found in the registry: {}".format( missing ) results = {} results.update(kwargs) results.update(await self.resolve(to_resolve)) return await method(self, **results) return inner bad = [0] class AsyncBase(metaclass=AsyncMeta): async def resolve(self, names): print(" resolve({})".format(names)) results = {} # Resolve them in the correct order ts = TopologicalSorter() ts2 = TopologicalSorter() print(" names = ", names) print(" self._graph = ", self._graph) for name in names: if self._graph[name]: ts.add(name, *self._graph[name]) ts2.add(name, *self._graph[name]) print(" static_order =", tuple(ts2.static_order())) ts.prepare() while ts.is_active(): print(" is_active, i = ", bad[0]) bad[0] += 1 if bad[0] > 20: print(" Infinite loop?") break nodes = ts.get_ready() print(" Do nodes:", nodes) awaitables = [self._registry[name](self, **{ k: v for k, v in results.items() if k in self._graph[name] }) for name in nodes] print(" awaitables: ", awaitables) awaitable_results = await asyncio.gather(*awaitables) results.update({ p[0].__name__: p[1] for p in zip(awaitables, awaitable_results) }) print(results) for node in nodes: ts.done(node) return results ``` Example usage: ```python class Foo(AsyncBase): async def graa(self, boff): print("graa") return 5 async def boff(self): print("boff") return 8 async def other(self, boff, graa): print("other") return 5 + boff + graa foo = Foo() await foo.other() ``` Output: ``` resolve(['boff', 'graa']) names = ['boff', 'graa'] self._graph = {'graa': {'boff'}, 'boff': set(), 'other': {'graa', 'boff'}} static_order = ('boff', 'graa') is_active, i = 0 Do nodes: ('boff',) awaitables: [<coroutine object Foo.boff at 0x10bd81a40>] resolve([]) names = [] self._graph = {'graa': {'boff'}, 'boff': set(), 'other': {'graa', 'boff'}} static_order = () boff {'boff': 8} is_active, i = 1 Do nodes: ('graa',) awaitables: [<coroutine object Foo.graa at 0x10d66b340>] resolve([]) names = [] self._graph = {'graa': {'boff'}, 'boff': set(), 'other': {'graa', 'boff'}} static_order = () graa {'boff': 8, 'graa': 5} other 18 ``` {"total_count": 0, "+1": 0, "-1": 0, "laugh": 0, "hooray": 0, "confused": 0, "heart": 0, "rocket": 0, "eyes": 0} 648435885