App deps check

src/cpl-application/cpl/application/abc/application_abc.py

@@ -22,8 +22,16 @@ class ApplicationABC(ABC):
     """
 
     @abstractmethod
-    def __init__(self, services: ServiceProviderABC):
+    def __init__(self, services: ServiceProviderABC, required_modules: list[str | object] = None):
         self._services = services
+        self._required_modules = [
+            x.__name__ if not isinstance(x, str) else x
+            for x in required_modules
+        ] if required_modules else []
+
+    @property
+    def required_modules(self) -> list[str]:
+        return self._required_modules
 
     @classmethod
     def extend(cls, name: str | Callable, func: Callable[[Self], Self]):

src/cpl-application/cpl/application/application_builder.py

@@ -6,6 +6,7 @@ from cpl.application.abc.application_extension_abc import ApplicationExtensionAB
 from cpl.application.abc.startup_abc import StartupABC
 from cpl.application.abc.startup_extension_abc import StartupExtensionABC
 from cpl.application.host import Host
+from cpl.core.errors import dependency_error
 from cpl.dependency.service_collection import ServiceCollection
 
 TApp = TypeVar("TApp", bound=ApplicationABC)
@@ -35,6 +36,18 @@ class ApplicationBuilder(Generic[TApp]):
     def service_provider(self):
         return self._services.build()
 
+    def validate_app_required_modules(self, app: ApplicationABC):
+        for module in app.required_modules:
+            if module in self._services.loaded_modules:
+                continue
+
+            dependency_error(
+                module,
+                ImportError(
+                    f"Required module '{module}' for application '{app.__class__.__name__}' is not loaded. Load using 'add_module({module})' method."
+                ),
+            )
+
     def with_startup(self, startup: Type[StartupABC]) -> "ApplicationBuilder":
         self._startup = startup
         return self
@@ -62,4 +75,6 @@ class ApplicationBuilder(Generic[TApp]):
         for extension in self._app_extensions:
             Host.run(extension.run, self.service_provider)
 
-        return self._app(self.service_provider)
+        app = self._app(self.service_provider)
+        self.validate_app_required_modules(app)
+        return app