refactor(WorkerManager): use attribute getters for type narrowing

questionpy_server/worker/runtime/manager.py

@@ -27,7 +27,6 @@
     LoadQPyPackage,
     MessageIds,
     MessageToServer,
-    MessageToWorker,
     ScoreAttempt,
     StartAttempt,
     ViewAttempt,
@@ -51,12 +50,12 @@ def register_on_request_callback(self, callback: OnRequestCallback) -> None:
 
 class WorkerManager:
     def __init__(self, server_connection: WorkerToServerConnection):
-        self.worker_type: str | None = None
+        self._worker_type: str | None = None
         self.server_connection: WorkerToServerConnection = server_connection
         self.limits: WorkerResourceLimits | None = None
         self.loaded_packages: dict[str, ImportablePackage] = {}
         self.main_package: ImportablePackage | None = None
-        self.question_type: BaseQuestionType | None = None
+        self._question_type: BaseQuestionType | None = None
         self.message_dispatch: dict[MessageIds, Callable[[Any], MessageToServer]] = {
             LoadQPyPackage.message_id: self.on_msg_load_qpy_package,
             GetQPyPackageManifest.message_id: self.on_msg_get_qpy_package_manifest,
@@ -74,7 +73,7 @@ def bootstrap(self) -> None:
             msg = f"'{InitWorker.__name__}' message expected, '{type(init_msg).__name__}' received"
             raise WorkerNotInitializedError(msg)
 
-        self.worker_type = init_msg.worker_type
+        self._worker_type = init_msg.worker_type
         self.limits = init_msg.limits
         if self.limits:
             # Limit memory usage.
@@ -96,12 +95,6 @@ def loop(self) -> None:
             self.server_connection.send_message(response)
 
     def on_msg_load_qpy_package(self, msg: LoadQPyPackage) -> MessageToServer:
-        self._require_init(msg)
-
-        if not self.worker_type:
-            errmsg = "'worker_type' is not set."
-            raise RuntimeError(errmsg)
-
         package = load_package(msg.location)
         package.setup_imports()
         self.loaded_packages[str(msg.location)] = package
@@ -121,37 +114,21 @@ def on_msg_load_qpy_package(self, msg: LoadQPyPackage) -> MessageToServer:
                 raise PackageInitFailedError(msg)
 
             self.main_package = package
-            self.question_type = qtype
+            self._question_type = qtype
 
         return LoadQPyPackage.Response()
 
     def on_msg_get_qpy_package_manifest(self, msg: GetQPyPackageManifest) -> MessageToServer:
-        self._require_init(msg)
-
         package = self.loaded_packages[msg.path]
         return GetQPyPackageManifest.Response(manifest=package.manifest)
 
     def on_msg_get_options_form_definition(self, msg: GetOptionsForm) -> MessageToServer:
-        self._require_init(msg)
-        self._require_main_package_loaded(msg)
-
-        if not self.question_type:
-            errmsg = "'question_type' is not set."
-            raise RuntimeError(errmsg)
-
         with self._with_request_user(msg.request_user):
             definition, form_data = self.question_type.get_options_form(msg.question_state)
 
             return GetOptionsForm.Response(definition=definition, form_data=form_data)
 
     def on_msg_create_question_from_options(self, msg: CreateQuestionFromOptions) -> CreateQuestionFromOptions.Response:
-        self._require_init(msg)
-        self._require_main_package_loaded(msg)
-
-        if not self.question_type:
-            errmsg = "'question_type' is not set."
-            raise RuntimeError(errmsg)
-
         with self._with_request_user(msg.request_user):
             question = self.question_type.create_question_from_options(msg.question_state, msg.form_data)
 
@@ -160,26 +137,12 @@ def on_msg_create_question_from_options(self, msg: CreateQuestionFromOptions) ->
             )
 
     def on_msg_start_attempt(self, msg: StartAttempt) -> StartAttempt.Response:
-        self._require_init(msg)
-        self._require_main_package_loaded(msg)
-
-        if not self.question_type:
-            errmsg = "'question_type' is not set."
-            raise RuntimeError(errmsg)
-
         with self._with_request_user(msg.request_user):
             question = self.question_type.create_question_from_state(msg.question_state)
             attempt = question.start_attempt(msg.variant)
             return StartAttempt.Response(attempt_state=attempt.export_attempt_state(), attempt_model=attempt.export())
 
     def on_msg_view_attempt(self, msg: ViewAttempt) -> ViewAttempt.Response:
-        self._require_init(msg)
-        self._require_main_package_loaded(msg)
-
-        if not self.question_type:
-            errmsg = "'question_type' is not set."
-            raise RuntimeError(errmsg)
-
         with self._with_request_user(msg.request_user):
             question = self.question_type.create_question_from_state(msg.question_state)
             attempt = question.get_attempt(
@@ -195,13 +158,6 @@ def on_msg_view_attempt(self, msg: ViewAttempt) -> ViewAttempt.Response:
             return ViewAttempt.Response(attempt_model=attempt.export())
 
     def on_msg_score_attempt(self, msg: ScoreAttempt) -> ScoreAttempt.Response:
-        self._require_init(msg)
-        self._require_main_package_loaded(msg)
-
-        if not self.question_type:
-            errmsg = "'question_type' is not set."
-            raise RuntimeError(errmsg)
-
         with self._with_request_user(msg.request_user):
             question = self.question_type.create_question_from_state(msg.question_state)
             attempt = question.get_attempt(
@@ -210,15 +166,19 @@ def on_msg_score_attempt(self, msg: ScoreAttempt) -> ScoreAttempt.Response:
             scored_model = attempt.export_scored_attempt()
             return ScoreAttempt.Response(attempt_scored_model=scored_model)
 
-    def _require_init(self, msg: MessageToWorker) -> None:
-        if not self.worker_type:
-            errmsg = f"'{InitWorker.__name__}' message expected, '{type(msg).__name__}' received"
+    @property
+    def worker_type(self) -> str:
+        if not self._worker_type:
+            errmsg = "'{InitWorker.__name__}' message expected"
             raise WorkerNotInitializedError(errmsg)
+        return self._worker_type
 
-    def _require_main_package_loaded(self, msg: MessageToWorker) -> None:
-        if not (self.main_package and self.loaded_packages and self.question_type):
-            errmsg = f"'{LoadQPyPackage.__name__}(main=True)' message expected, '{type(msg).__name__}' received"
+    @property
+    def question_type(self) -> BaseQuestionType:
+        if not self._question_type:
+            errmsg = f"'{LoadQPyPackage.__name__}(main=True)' message expected"
             raise MainPackageNotLoadedError(errmsg)
+        return self._question_type
 
     @contextmanager
     def _with_request_user(self, request_user: RequestUser) -> Generator[None, None, None]: