Refactor wiring module

src/dependency_injector/wiring.py

@@ -136,26 +136,10 @@ class ProvidersMap:
             try:
                 provider = getattr(provider, segment)
             except AttributeError:
-                return
+                return None
 
-        if isinstance(modifier, TypeModifier):
-            provider = provider.as_(modifier.type_)
-        elif isinstance(modifier, RequiredModifier):
-            provider = provider.required()
-            if modifier.type_modifier:
-                provider = provider.as_(modifier.type_modifier.type_)
-        elif isinstance(modifier, InvariantModifier):
-            invariant_segment = self._resolve_string_id(modifier.id)
-            provider = provider[invariant_segment]
-        elif isinstance(modifier, ProvidedInstance):
-            provider = provider.provided
-            for type_, value in modifier.segments:
-                if type_ == ProvidedInstance.TYPE_ATTRIBUTE:
-                    provider = getattr(provider, value)
-                elif type_ == ProvidedInstance.TYPE_ITEM:
-                    provider = provider[value]
-                elif type_ == ProvidedInstance.TYPE_CALL:
-                    provider = provider.call()
+        if modifier:
+            provider = modifier.modify(provider, providers_map=self)
         return provider
 
     def _resolve_provided_instance(
@@ -230,7 +214,7 @@ class ProvidersMap:
         try:
             return self._map[original]
         except KeyError:
-            pass
+            return None
 
     @classmethod
     def _create_providers_map(
@@ -563,13 +547,19 @@ def _is_declarative_container(instance: Any) -> bool:
 
 
 class Modifier:
-    ...
+
+    def modify(self, provider: providers.ConfigurationOption, providers_map: ProvidersMap) -> providers.Provider:
+        ...
 
 
 class TypeModifier(Modifier):
+
     def __init__(self, type_: Type):
         self.type_ = type_
 
+    def modify(self, provider: providers.ConfigurationOption, providers_map: ProvidersMap) -> providers.Provider:
+        return provider.as_(self.type_)
+
 
 def as_int() -> TypeModifier:
     """Return int type modifier."""
@@ -587,6 +577,7 @@ def as_(type_: Type) -> TypeModifier:
 
 
 class RequiredModifier(Modifier):
+
     def __init__(self):
         self.type_modifier = None
 
@@ -604,6 +595,12 @@ class RequiredModifier(Modifier):
         self.type_modifier = TypeModifier(type_)
         return self
 
+    def modify(self, provider: providers.ConfigurationOption, providers_map: ProvidersMap) -> providers.Provider:
+        provider = provider.required()
+        if self.type_modifier:
+            provider = provider.as_(self.type_modifier.type_)
+        return provider
+
 
 def required() -> RequiredModifier:
     """Return required modifier."""
@@ -611,9 +608,14 @@ def required() -> RequiredModifier:
 
 
 class InvariantModifier(Modifier):
+
     def __init__(self, id: str) -> None:
         self.id = id
 
+    def modify(self, provider: providers.ConfigurationOption, providers_map: ProvidersMap) -> providers.Provider:
+        invariant_segment = providers_map.resolve_provider(self.id)
+        return provider[invariant_segment]
+
 
 def invariant(id: str) -> InvariantModifier:
     """Return invariant modifier."""
@@ -641,6 +643,17 @@ class ProvidedInstance(Modifier):
         self.segments.append((self.TYPE_CALL, None))
         return self
 
+    def modify(self, provider: providers.ConfigurationOption, providers_map: ProvidersMap) -> providers.Provider:
+        provider = provider.provided
+        for type_, value in self.segments:
+            if type_ == ProvidedInstance.TYPE_ATTRIBUTE:
+                provider = getattr(provider, value)
+            elif type_ == ProvidedInstance.TYPE_ITEM:
+                provider = provider[value]
+            elif type_ == ProvidedInstance.TYPE_CALL:
+                provider = provider.call()
+        return provider
+
 
 def provided() -> ProvidedInstance:
     """Return provided instance modifier."""