fix: various DI improvements

fragments/449.bugfix.md

@@ -0,0 +1,5 @@
+- Improved container hierarchical dependency resolution process.
+- Add significantly more `DEBUG` logging throughout the DI pipeline.
+- `DependencyInjectionManager.enter_context` now needs to be called for every context you wish to enter; it will no longer enter the default context automatically.
+- `DependencyInjectionManager.enter_context` now searches the existing container hierarchy to find an existing container for the passed context before trying to create a new one.
+- `DependencyInjectionManager.enter_context` now returns a no-op container implementation instead of `None` if DI is disabled globally.

lightbulb/client.py

@@ -946,9 +946,11 @@
     async def _execute_autocomplete_context(
         self, context: context_.AutocompleteContext[t.Any], autocomplete_provider: options_.AutocompleteProvider[t.Any]
     ) -> None:
-        async with self.di.enter_context(di_.Contexts.AUTOCOMPLETE) as container:
-            if container is not None:  # type: ignore[reportUnnecessaryComparison]
-                container.add_value(context_.AutocompleteContext, context)
+        async with (
+            self.di.enter_context(di_.Contexts.DEFAULT),
+            self.di.enter_context(di_.Contexts.AUTOCOMPLETE) as container,
+        ):
+            container.add_value(context_.AutocompleteContext, context)
 
             try:
                 await autocomplete_provider(context)
@@ -1015,10 +1017,12 @@
     async def _execute_command_context(self, context: context_.Context) -> None:
         pipeline = execution.ExecutionPipeline(context, self.execution_step_order)
 
-        async with self.di.enter_context(di_.Contexts.COMMAND) as container:
-            if container is not None:  # type: ignore[reportUnnecessaryComparison]
-                container.add_value(context_.Context, context)
-                container.add_value(execution.ExecutionPipeline, pipeline)
+        async with (
+            self.di.enter_context(di_.Contexts.DEFAULT),
+            self.di.enter_context(di_.Contexts.COMMAND) as container,
+        ):
+            container.add_value(context_.Context, context)
+            container.add_value(execution.ExecutionPipeline, pipeline)
 
             try:
                 await pipeline._run()

lightbulb/di/container.py

@@ -22,6 +22,7 @@
 
 __all__ = ["Container"]
 
+import logging
 import typing as t
 
 import networkx as nx
@@ -35,9 +36,11 @@
     import types
     from collections.abc import Callable
 
+    from lightbulb.di import solver
     from lightbulb.internal import types as lb_types
 
 T = t.TypeVar("T")
+LOGGER = logging.getLogger(__name__)
 
 
 class Container:
@@ -49,33 +52,22 @@ class Container:
         parent: The parent container. Defaults to None.
     """
 
-    __slots__ = ("_closed", "_graph", "_instances", "_parent", "_registry")
+    __slots__ = ("_closed", "_graph", "_instances", "_parent", "_registry", "_tag")
 
-    def __init__(self, registry: registry_.Registry, *, parent: Container | None = None) -> None:
+    def __init__(
+        self, registry: registry_.Registry, *, parent: Container | None = None, tag: solver.Context | None = None
+    ) -> None:
         self._registry = registry
         self._registry._freeze(self)
+
         self._parent = parent
+        self._tag = tag
 
         self._closed = False
 
-        self._graph: nx.DiGraph[str] = nx.DiGraph(self._parent._graph) if self._parent is not None else nx.DiGraph()
+        self._graph: nx.DiGraph[str] = nx.DiGraph(self._registry._graph)
         self._instances: dict[str, t.Any] = {}
 
-        # Add our registry entries to the graphs
-        for node, node_data in self._registry._graph.nodes.items():
-            new_node_data = dict(node_data)
-
-            # Set the origin container if this is a concrete dependency instead of a transient one
-            if node_data.get("factory") is not None:
-                new_node_data["container"] = self
-
-            # If we are overriding a previously defined dependency with our own
-            if node in self._graph and node_data.get("factory") is not None:
-                self._graph.remove_edges_from(list(self._graph.out_edges(node)))
-
-            self._graph.add_node(node, **new_node_data)
-        self._graph.add_edges_from(self._registry._graph.edges)
-
         self.add_value(Container, self)
 
     async def __aenter__(self) -> Container:
@@ -152,23 +144,25 @@ def add_value(
 
         if dependency_id in self._graph:
             self._graph.remove_edges_from(list(self._graph.out_edges(dependency_id)))
-        self._graph.add_node(dependency_id, container=self, teardown=teardown)
+        self._graph.add_node(dependency_id, factory=lambda: None, teardown=teardown)
 
     async def _get(self, dependency_id: str) -> t.Any:
         if self._closed:
             raise exceptions.ContainerClosedException
 
         # TODO - look into whether locking is necessary - how likely are we to have race conditions
 
-        data = self._graph.nodes.get(dependency_id)
-        if data is None or data.get("container") is None:
-            raise exceptions.DependencyNotSatisfiableException(
-                f"could not create dependency {dependency_id!r} - not provided by this or a parent container"
-            )
+        if (existing := self._instances.get(dependency_id)) is not None:
+            return existing
 
-        existing_dependency = data["container"]._instances.get(dependency_id)
-        if existing_dependency is not None:
-            return existing_dependency
+        if (data := self._graph.nodes.get(dependency_id)) is None or data.get("factory") is None:
+            if self._parent is None:
+                raise exceptions.DependencyNotSatisfiableException(
+                    f"cannot create dependency {dependency_id!r} - not provided by this or a parent container"
+                )
+
+            LOGGER.debug("dependency %r not provided by this container - checking parent", dependency_id)
+            return await self._parent._get(dependency_id)
 
         # TODO - look into caching individual dependency creation order globally
         #      - may speed up using subsequent containers (i.e. for each command)
@@ -177,47 +171,38 @@ async def _get(self, dependency_id: str) -> t.Any:
         assert isinstance(subgraph, nx.DiGraph)
 
         try:
-            creation_order = reversed(list(nx.topological_sort(subgraph)))
+            creation_order = list(reversed(list(nx.topological_sort(subgraph))))
         except nx.NetworkXUnfeasible:
             raise exceptions.CircularDependencyException(
                 f"cannot provide {dependency_id!r} - circular dependency found during creation"
             )
 
+        LOGGER.debug("dependency %r depends on %s", dependency_id, creation_order[:-1])
         for dep_id in creation_order:
-            if (container := self._graph.nodes[dep_id].get("container")) is None:
-                raise exceptions.DependencyNotSatisfiableException(
-                    f"could not create dependency {dep_id!r} - not provided by this or a parent container"
-                )
-
             # We already have the dependency we need
-            if dep_id in container._instances:
+            if dep_id in self._instances:
                 continue
 
             node_data = self._graph.nodes[dep_id]
-            # Check that we actually know how to create the dependency - this should have been caught earlier
-            # by checking that node["container"] was present - but just in case, we check for the factory
             if node_data.get("factory") is None:
                 raise exceptions.DependencyNotSatisfiableException(
                     f"could not create dependency {dep_id!r} - do not know how to instantiate"
                 )
 
-            # Get the dependencies for this dependency from the container this dependency was defined in.
-            # This prevents 'scope promotion' - a dependency from the parent container requiring one from the
-            # child container, and hence the lifecycle of the child dependency being extended to
-            # that of the parent.
             sub_dependencies: dict[str, t.Any] = {}
             try:
+                LOGGER.debug("checking sub-dependencies for %r", dep_id)
                 for sub_dependency_id, param_name in node_data["factory_params"].items():
-                    sub_dependencies[param_name] = await node_data["container"]._get(sub_dependency_id)
+                    sub_dependencies[param_name] = await self._get(sub_dependency_id)
             except exceptions.DependencyNotSatisfiableException as e:
                 raise exceptions.DependencyNotSatisfiableException(
                     f"could not create dependency {dep_id!r} - failed creating sub-dependency"
                 ) from e
 
             # Cache the created dependency in the correct container to ensure the correct lifecycle
-            container._instances[dep_id] = await utils.maybe_await(node_data["factory"](**sub_dependencies))
+            self._instances[dep_id] = await utils.maybe_await(node_data["factory"](**sub_dependencies))
 
-        return self._graph.nodes[dependency_id]["container"]._instances[dependency_id]
+        return self._instances[dependency_id]
 
     async def get(self, typ: type[T]) -> T:
         """

lightbulb/di/solver.py

@@ -43,10 +43,6 @@
 import os
 import sys
 import typing as t
-from collections.abc import AsyncIterator
-from collections.abc import Awaitable
-from collections.abc import Callable
-from collections.abc import Coroutine
 
 from lightbulb import utils
 from lightbulb.di import container
@@ -55,11 +51,16 @@
 from lightbulb.internal import marker
 
 if t.TYPE_CHECKING:
-    from lightbulb.internal import types
+    from collections.abc import AsyncIterator
+    from collections.abc import Awaitable
+    from collections.abc import Callable
+    from collections.abc import Coroutine
+
+    from lightbulb.internal import types as lb_types
 
 P = t.ParamSpec("P")
 R = t.TypeVar("R")
-AsyncFnT = t.TypeVar("AsyncFnT", bound=Callable[..., Coroutine[t.Any, t.Any, t.Any]])
+T = t.TypeVar("T")
 
 DI_ENABLED: t.Final[bool] = os.environ.get("LIGHTBULB_DI_DISABLED", "false").lower() != "true"
 DI_CONTAINER: contextvars.ContextVar[container.Container | None] = contextvars.ContextVar(
@@ -132,6 +133,32 @@ class Contexts:
 }
 
 
+class _NoOpContainer(container.Container):
+    __slots__ = ()
+
+    def add_factory(
+        self,
+        typ: type[T],
+        factory: Callable[..., lb_types.MaybeAwaitable[T]],
+        *,
+        teardown: Callable[[T], lb_types.MaybeAwaitable[None]] | None = None,
+    ) -> None: ...
+
+    def add_value(
+        self,
+        typ: type[T],
+        value: T,
+        *,
+        teardown: Callable[[T], lb_types.MaybeAwaitable[None]] | None = None,
+    ) -> None: ...
+
+    def _get(self, dependency_id: str) -> t.Any:
+        raise exceptions.DependencyNotSatisfiableException("dependency injection is globally disabled")
+
+
+_NOOP_CONTAINER = _NoOpContainer(registry.Registry(), tag=Contexts.DEFAULT)
+
+
 class DependencyInjectionManager:
     """Class which contains dependency injection functionality."""
 
@@ -167,9 +194,8 @@ async def enter_context(self, context: Context = Contexts.DEFAULT, /) -> AsyncIt
         Context manager that ensures a dependency injection context is available for the nested operations.
 
         Args:
-            context: The context to enter. If you are trying to enter a non-default (:obj:`~DiContext.DEFAULT`) context,
-                the default context will be entered first to ensure its dependencies are available. Defaults to
-                :obj:`~DiContext.DEFAULT`.
+            context: The context to enter. If a container for the given context already exists, it will be returned
+                and a new container will not be created.
 
         Yields:
             :obj:`~lightbulb.di.container.Container`: The container that has been entered.
@@ -179,50 +205,74 @@ async def enter_context(self, context: Context = Contexts.DEFAULT, /) -> AsyncIt
             .. code-block:: python
 
                 # Enter a specific context ('client' is your lightbulb.Client instance)
-                with client.di.enter_context(lightbulb.di.DiContext.COMMAND):
+                async with client.di.enter_context(lightbulb.di.Contexts.COMMAND):
                     await some_function_that_needs_dependencies()
 
+        Note:
+            If you want to enter multiple contexts - i.e. a command context that requires the default context to
+            be available first - you should call this once for each context that is needed.
+
+            .. code-block:: python
+
+                async with (
+                    client.di.enter_context(lightbulb.di.Contexts.DEFAULT),
+                    client.di.enter_context(lightbulb.di.Contexts.COMMAND)
+                ):
+                    ...
+
         Warning:
             If you have disabled dependency injection using the ``LIGHTBULB_DI_DISABLED`` environment variable,
             this method will do nothing and the context manager will return :obj:`None`. Most users will never
             have to worry about this, but it is something to consider. The type-hint does not reflect this
             to prevent your type-checker complaining about not checking for :obj:`None`.
         """
         if not DI_ENABLED:
-            # I'm not sure how to deal with this - but I definitely don't want to hint the return type
-            # as optional because that adds annoying assertions further down the line for users
-            #
-            # I think I should just account for this internally within the library and document the
-            # behaviour - chances are almost all users will never come across this
-            yield None  # type: ignore
+            # Return a container that will never register dependencies and cannot have dependencies
+            # retrieved from it - it will always raise an error if someone tries to use DI while it is
+            # globally disabled.
+            yield _NOOP_CONTAINER
             return
 
-        initial_token, initial = None, DI_CONTAINER.get(None)
-        if initial is None:
-            if self._default_container is None:
-                self._default_container = container.Container(self._registries[Contexts.DEFAULT])
-                self._default_container.add_value(DefaultContainer, self._default_container)
+        LOGGER.debug("attempting to enter context %r", context)
+
+        new_container: container.Container | None = None
+        created: bool = False
+
+        token, value = None, DI_CONTAINER.get(None)
+        if value is not None:
+            LOGGER.debug("searching for existing container for context %r", context)
+            this = value
+            while this:
+                if this._tag == context:
+                    new_container = this
+                    LOGGER.debug("existing container found for context %r", context)
+                    break
 
-            initial_token = DI_CONTAINER.set(self._default_container)
+                this = this._parent
 
-        ctx_token: contextvars.Token[container.Container | None] | None = None
-        if context != Contexts.DEFAULT:
-            new_container = container.Container(self._registries[context], parent=DI_CONTAINER.get())
+        if new_container is None:
+            LOGGER.debug("creating new container for context %r", context)
+
+            new_container = container.Container(self._registries[context], parent=value, tag=context)
             new_container.add_value(_CONTAINER_TYPE_BY_CONTEXT[context], new_container)
-            ctx_token = DI_CONTAINER.set(new_container)
+
+            if context == Contexts.DEFAULT:
+                self._default_container = new_container
+
+            created = True
+
+        token = DI_CONTAINER.set(new_container)
+        LOGGER.debug("entered context %r", context)
 
         try:
-            if (ct := DI_CONTAINER.get(None)) is not None:
-                if ct is self.default_container:
-                    yield ct
-                else:
-                    async with ct:
-                        yield ct
+            if new_container is self._default_container or not created:
+                yield new_container
+            else:
+                async with new_container:
+                    yield new_container
         finally:
-            if ctx_token is not None:
-                DI_CONTAINER.reset(ctx_token)
-            if initial_token is not None:
-                DI_CONTAINER.reset(initial_token)
+            DI_CONTAINER.reset(token)
+            LOGGER.debug("cleared context %r", context)
 
     async def close(self) -> None:
         """
@@ -237,7 +287,7 @@ async def close(self) -> None:
             self._default_container = None
 
 
-CANNOT_INJECT = object()
+CANNOT_INJECT: t.Final[t.Any] = marker.Marker("CANNOT_INJECT")
 
 
 def _parse_injectable_params(func: Callable[..., t.Any]) -> tuple[list[tuple[str, t.Any]], dict[str, t.Any]]:
@@ -336,14 +386,19 @@ async def __call__(self, *args: t.Any, **kwargs: t.Any) -> t.Any:
             if di_container is None:
                 raise exceptions.DependencyNotSatisfiableException("no DI context is available")
 
+            LOGGER.debug("requesting dependency for type %r", type)
             new_kwargs[name] = await di_container.get(type)
 
+        if len(new_kwargs) > len(kwargs):
+            func_name = ((self._self.__class__.__name__ + ".") if self._self else "") + self._func.__name__
+            LOGGER.debug("calling function %r with resolved dependencies", func_name)
+
         if self._self is not None:
             return await utils.maybe_await(self._func(self._self, *args, **new_kwargs))
         return await utils.maybe_await(self._func(*args, **new_kwargs))
 
 
-def with_di(func: Callable[P, types.MaybeAwaitable[R]]) -> Callable[P, Coroutine[t.Any, t.Any, R]]:
+def with_di(func: Callable[P, lb_types.MaybeAwaitable[R]]) -> Callable[P, Coroutine[t.Any, t.Any, R]]:
     """
     Decorator that enables dependency injection on the decorated function. If dependency injection
     has been disabled globally then this function does nothing and simply returns the object that was passed in.