refactor: Polymorphism instead of inspection

Author: davidparsson

injector/__init__.py

@@ -344,12 +344,18 @@ def __repr__(self) -> str:
 class MultiBinder(Provider, Generic[T]):
     """Provide a list of instances via other Providers."""
 
+    __metaclass__ = ABCMeta
+
     _multi_bindings: List['Binding']
 
     def __init__(self, parent: 'Binder') -> None:
         self._multi_bindings = []
         self._binder = Binder(parent.injector, auto_bind=False, parent=parent)
 
+    @abstractmethod
+    def multbind(self, interface: type, to: Any, scope: Union['ScopeDecorator', Type['Scope'], None]) -> None:
+        raise NotImplementedError
+
     def append(self, provider: Provider[T], scope: Type['Scope']) -> None:
         # HACK: generate a pseudo-type for this element in the list.
         # This is needed for scopes to work properly. Some, like the Singleton scope,
@@ -372,6 +378,21 @@ class MultiBindProvider(MultiBinder[List[T]]):
     """Used by :meth:`Binder.multibind` to flatten results of providers that
     return sequences."""
 
+    def multibind(
+        self, interface: type, to: Any, scope: Union['ScopeDecorator', Type['Scope'], None]
+    ) -> None:
+        try:
+            element_type = get_args(_punch_through_alias(interface))[0]
+        except IndexError:
+            raise InvalidInterface(f"Use typing.List[T] or list[T] to specify the element type of the list")
+        if isinstance(to, list):
+            for element in to:
+                element_binding = self._binder.create_binding(element_type, element, scope)
+                self.append(element_binding.provider, element_binding.scope)
+        else:
+            element_binding = self._binder.create_binding(interface, to, scope)
+            self.append(element_binding.provider, element_binding.scope)
+
     def get(self, injector: 'Injector') -> List[T]:
         result: List[T] = []
         for provider in self.get_scoped_providers(injector):
@@ -383,6 +404,23 @@ def get(self, injector: 'Injector') -> List[T]:
 class MapBindProvider(MultiBinder[Dict[str, T]]):
     """A provider for map bindings."""
 
+    def multibind(
+        self, interface: type, to: Any, scope: Union['ScopeDecorator', Type['Scope'], None]
+    ) -> None:
+        try:
+            value_type = get_args(_punch_through_alias(interface))[1]
+        except IndexError:
+            raise InvalidInterface(
+                f"Use typing.Dict[K, V] or dict[K, V] to specify the value type of the dict"
+            )
+        if isinstance(to, dict):
+            for key, value in to.items():
+                element_binding = self._binder.create_binding(value_type, value, scope)
+                self.append(KeyValueProvider(key, element_binding.provider), element_binding.scope)
+        else:
+            element_binding = self._binder.create_binding(interface, to, scope)
+            self.append(element_binding.provider, element_binding.scope)
+
     def get(self, injector: 'Injector') -> Dict[str, T]:
         map: Dict[str, T] = {}
         for provider in self.get_scoped_providers(injector):
@@ -549,29 +587,7 @@ def multibind(
         :param scope: Optional Scope in which to bind.
         """
         multi_binder = self._get_multi_binder(interface)
-        if isinstance(multi_binder, MultiBindProvider) and isinstance(to, list):
-            try:
-                element_type = get_args(_punch_through_alias(interface))[0]
-            except IndexError:
-                raise InvalidInterface(
-                    f"Use typing.List[T] or list[T] to specify the element type of the list"
-                )
-            for element in to:
-                element_binding = self.create_binding(element_type, element, scope)
-                multi_binder.append(element_binding.provider, element_binding.scope)
-        elif isinstance(multi_binder, MapBindProvider) and isinstance(to, dict):
-            try:
-                value_type = get_args(_punch_through_alias(interface))[1]
-            except IndexError:
-                raise InvalidInterface(
-                    f"Use typing.Dict[K, V] or dict[K, V] to specify the value type of the dict"
-                )
-            for key, value in to.items():
-                element_binding = self.create_binding(value_type, value, scope)
-                multi_binder.append(KeyValueProvider(key, element_binding.provider), element_binding.scope)
-        else:
-            element_binding = self.create_binding(interface, to, scope)
-            multi_binder.append(element_binding.provider, element_binding.scope)
+        multi_binder.multibind(interface, to, scope)
 
     def _get_multi_binder(self, interface: type) -> MultiBinder:
         multi_binder: MultiBinder