Merge pull request #12 from BradLewis/develop

Adding optional arguments and better error messaging.

examples/flask/flask_inject_create_app.py

@@ -27,7 +27,7 @@ def __init__(self, db_service: IDatabaseService):
 
     def get_by_id(self, id: int):
         query = "SELECT * FROM users WHERE id = ?"
-        result = self._db_serive.run_query(query, id)
+        result = self._db_service.run_query(query, id)
         return {"name": "test name", "id": id}
 
 

simple_injection/service_collection.py

@@ -59,6 +59,12 @@ def __init__(
         self.implementations: List[Union[Type[T], T]] = list()
 
 
+class ServiceResolutionError(Exception):
+    def __init__(self, message, errors, service):
+        super().__init__(message, errors)
+        self.service = service
+
+
 class ServiceCollection:
     def __init__(self):
         self._service_collection: Dict[Type[T], _ContainerService] = dict()
@@ -200,14 +206,29 @@ def resolve(self, service_to_resolve: Type[T]) -> T:
         Returns:
             T: An instance of the resolved service.
         """
-        container_service = self._service_collection[service_to_resolve]
-        if container_service.multiple_implementations:
-            return self._resolve_multiple(container_service)
-        if container_service.service_lifetime == ServiceLifetime.INSTANCE:
-            return self._resolve_instance(container_service)
-        if container_service.service_lifetime == ServiceLifetime.SINGLETON:
-            return self._resolve_singleton(container_service)
-        return self._resolve_annotations(container_service)
+        if self._is_optional(service_to_resolve):
+            return self._handle_optional(service_to_resolve)
+        if service_to_resolve not in self._service_collection:
+            raise ValueError(
+                f"Service {service_to_resolve} not found in the collection. Ensure {service_to_resolve} has been added to the collection."
+            )
+        try:
+            container_service = self._service_collection[service_to_resolve]
+            if container_service.multiple_implementations:
+                return self._resolve_multiple(container_service)
+            if container_service.service_lifetime == ServiceLifetime.INSTANCE:
+                return self._resolve_instance(container_service)
+            if container_service.service_lifetime == ServiceLifetime.SINGLETON:
+                return self._resolve_singleton(container_service)
+            return self._resolve_annotations(container_service)
+        except ServiceResolutionError as e:
+            raise e
+        except Exception as e:
+            raise ServiceResolutionError(
+                f"Exception occurred trying to resolve {service_to_resolve}",
+                e,
+                service_to_resolve,
+            )
 
     def _resolve_multiple(self, container_service: _ContainerService):
         services_to_resolve = container_service.implementations
@@ -249,6 +270,13 @@ def _resolve_args(self, container_service: _ContainerService):
             args.append(arg)
         return container_service.service_implementation(*args)
 
+    def _handle_optional(self, service_to_resolve: Type[T]):
+        to_resolve = service_to_resolve.__args__[0]
+        if to_resolve in self._service_collection:
+            return self.resolve(to_resolve)
+        else:
+            return None
+
     def _create_list_service(self, service_to_add):
         service = self._service_collection[service_to_add]
         self.add(
@@ -262,3 +290,11 @@ def _create_list_service(self, service_to_add):
         self._service_collection[List[service_to_add]].implementations.append(
             service.service_implementation
         )
+
+    def _is_optional(self, service_to_resolve: Type[T]):
+        if not hasattr(service_to_resolve, "__args__"):
+            return False
+        args = service_to_resolve.__args__
+        if len(args) != 2:
+            return False
+        return args[-1] == type(None)

tests/test_exceptions.py

@@ -0,0 +1,26 @@
+from simple_injection.service_collection import ServiceResolutionError
+import pytest
+from tests.classes import A, B, C
+from simple_injection import ServiceCollection
+
+
+class D:
+    def __init__(self, b: B):
+        self._b = b
+
+
+def test_resolution_error():
+    collection = ServiceCollection()
+    collection.add_transient(B)
+
+    with pytest.raises(ServiceResolutionError):
+        collection.resolve(B)
+
+
+def test_nested_resolution_error():
+    collection = ServiceCollection()
+    collection.add_transient(D)
+    collection.add_transient(B)
+
+    with pytest.raises(ServiceResolutionError):
+        collection.resolve(D)

tests/test_optional.py

@@ -0,0 +1,48 @@
+from simple_injection import ServiceCollection
+from typing import Optional
+from tests.classes import A, B, C
+
+
+class HasOptional:
+    def __init__(self, a: A, b: Optional[B] = None):
+        self._a = a
+        self._b = b
+
+
+class HasOptionalWithDeps:
+    def __init__(self, a: A, c: Optional[C] = None):
+        self._a = a
+        self._c = c
+
+
+def test_optional_declared():
+    collection = ServiceCollection()
+    collection.add_transient(A)
+    collection.add_transient(B)
+    collection.add_transient(HasOptional)
+
+    has_optional = collection.resolve(HasOptional)
+    assert isinstance(has_optional._a, A)
+    assert isinstance(has_optional._b, B)
+
+
+def test_optional_not_declared():
+    collection = ServiceCollection()
+    collection.add_transient(A)
+    collection.add_transient(HasOptional)
+
+    has_optional = collection.resolve(HasOptional)
+    assert isinstance(has_optional._a, A)
+    assert has_optional._b is None
+
+
+def test_optional_with_dependencies():
+    collection = ServiceCollection()
+    collection.add_transient(A)
+    collection.add_transient(B)
+    collection.add_transient(C)
+    collection.add_transient(HasOptionalWithDeps)
+
+    has_optional_with_deps = collection.resolve(HasOptionalWithDeps)
+    assert isinstance(has_optional_with_deps._a, A)
+    assert isinstance(has_optional_with_deps._c, C)