refactoring: ♻️ scope.py

injection/_core/scope.py

@@ -1,12 +1,13 @@
 from __future__ import annotations
 
+import itertools
 from abc import ABC, abstractmethod
 from collections import defaultdict
-from collections.abc import AsyncIterator, Iterator, MutableMapping
+from collections.abc import AsyncIterator, Iterator, Mapping, MutableMapping
 from contextlib import AsyncExitStack, ExitStack, asynccontextmanager, contextmanager
 from contextvars import ContextVar
 from dataclasses import dataclass, field
-from types import TracebackType
+from types import EllipsisType, TracebackType
 from typing import (
     Any,
     AsyncContextManager,
@@ -15,6 +16,7 @@
     NoReturn,
     Protocol,
     Self,
+    overload,
     runtime_checkable,
 )
 
@@ -26,32 +28,43 @@
 )
 
 
-@dataclass(repr=False, slots=True)
-class _ScopeState:
-    # Shouldn't be instantiated outside `__SCOPES`.
+@runtime_checkable
+class ScopeState(Protocol):
+    __slots__ = ()
+
+    @property
+    @abstractmethod
+    def active_scopes(self) -> Iterator[Scope]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def bind(self, scope: Scope) -> ContextManager[None]:
+        raise NotImplementedError
+
+    @abstractmethod
+    def get_scope(self) -> Scope | None:
+        raise NotImplementedError
+
+
+@dataclass(repr=False, frozen=True, slots=True)
+class _ContextualScopeState(ScopeState):
+    # Shouldn't be instantiated outside `__CONTEXTUAL_SCOPES`.
 
     __context_var: ContextVar[Scope] = field(
         default_factory=lambda: ContextVar(f"scope@{new_short_key()}"),
         init=False,
     )
-    __default: Scope | None = field(
-        default=None,
-        init=False,
-    )
     __references: set[Scope] = field(
         default_factory=set,
         init=False,
     )
 
     @property
     def active_scopes(self) -> Iterator[Scope]:
-        yield from self.__references
-
-        if default := self.__default:
-            yield default
+        return iter(self.__references)
 
     @contextmanager
-    def bind_contextual_scope(self, scope: Scope) -> Iterator[None]:
+    def bind(self, scope: Scope) -> Iterator[None]:
         self.__references.add(scope)
         token = self.__context_var.set(scope)
 
@@ -61,26 +74,38 @@ def bind_contextual_scope(self, scope: Scope) -> Iterator[None]:
             self.__context_var.reset(token)
             self.__references.remove(scope)
 
-    @contextmanager
-    def bind_shared_scope(self, scope: Scope) -> Iterator[None]:
-        if next(self.active_scopes, None):
-            raise ScopeError(
-                "A shared scope can't be defined when one or more contextual scopes "
-                "are defined on the same name."
-            )
+    def get_scope(self) -> Scope | None:
+        return self.__context_var.get(None)
+
+
+@dataclass(repr=False, slots=True)
+class _SharedScopeState(ScopeState):
+    __scope: Scope | None = field(default=None)
+
+    @property
+    def active_scopes(self) -> Iterator[Scope]:
+        if scope := self.__scope:
+            yield scope
 
-        self.__default = scope
+    @contextmanager
+    def bind(self, scope: Scope) -> Iterator[None]:
+        self.__scope = scope
 
         try:
             yield
         finally:
-            self.__default = None
+            self.__scope = None
 
     def get_scope(self) -> Scope | None:
-        return self.__context_var.get(self.__default)
+        return self.__scope
 
 
-__SCOPES: Final[defaultdict[str, _ScopeState]] = defaultdict(_ScopeState)
+__CONTEXTUAL_SCOPES: Final[Mapping[str, ScopeState]] = defaultdict(
+    _ContextualScopeState,
+)
+__SHARED_SCOPES: Final[Mapping[str, ScopeState]] = defaultdict(
+    _SharedScopeState,
+)
 
 
 @asynccontextmanager
@@ -98,36 +123,52 @@ def define_scope(name: str, *, shared: bool = False) -> Iterator[None]:
 
 
 def get_active_scopes(name: str) -> tuple[Scope, ...]:
-    state = __SCOPES.get(name)
+    active_scopes = (
+        state.active_scopes
+        for states in (__CONTEXTUAL_SCOPES, __SHARED_SCOPES)
+        if (state := states.get(name))
+    )
+    return tuple(itertools.chain.from_iterable(active_scopes))
+
 
-    if state is None:
-        return ()
+@overload
+def get_scope(name: str, default: EllipsisType = ...) -> Scope: ...
 
-    return tuple(state.active_scopes)
 
+@overload
+def get_scope[T](name: str, default: T) -> Scope | T: ...
 
-def get_scope(name: str) -> Scope:
-    state = __SCOPES.get(name)
 
-    if state is None or (scope := state.get_scope()) is None:
+def get_scope(name, default=...):  # type: ignore[no-untyped-def]
+    for states in (__CONTEXTUAL_SCOPES, __SHARED_SCOPES):
+        state = states.get(name)
+        if state and (scope := state.get_scope()):
+            return scope
+
+    if default is Ellipsis:
         raise ScopeUndefinedError(
             f"Scope `{name}` isn't defined in the current context."
         )
 
-    return scope
+    return default
 
 
 @contextmanager
 def _bind_scope(name: str, scope: Scope, shared: bool) -> Iterator[None]:
-    state = __SCOPES[name]
+    if shared:
+        is_already_defined = bool(get_active_scopes(name))
+        state = __SHARED_SCOPES[name]
+
+    else:
+        is_already_defined = bool(get_scope(name, default=None))
+        state = __CONTEXTUAL_SCOPES[name]
 
-    if state.get_scope():
+    if is_already_defined:
         raise ScopeAlreadyDefinedError(
             f"Scope `{name}` is already defined in the current context."
         )
 
-    strategy = state.bind_shared_scope if shared else state.bind_contextual_scope
-    with strategy(scope):
+    with state.bind(scope):
         yield