fix: catch possible pickling errors (#118)

### Summary of Changes

Catch pickling errors in two other locations where they might occur.

---------

Co-authored-by: megalinter-bot <129584137+megalinter-bot@users.noreply.github.com>

src/safeds_runner/cli/_cli.py

@@ -42,6 +42,8 @@ def _get_args() -> argparse.Namespace:  # pragma: no cover
     return parser.parse_args()
 
 
-def _add_start_subparser(subparsers: argparse._SubParsersAction) -> None:  # pragma: no cover
+def _add_start_subparser(
+    subparsers: argparse._SubParsersAction,
+) -> None:  # pragma: no cover
     parser = subparsers.add_parser(Commands.START, help="start the Safe-DS Runner server")
     parser.add_argument("-p", "--port", type=int, default=5000, help="the port to use")

src/safeds_runner/memoization/_memoization_map.py

@@ -181,7 +181,18 @@ def memoized_function_call(
         memoizable_value = _wrap_value_to_shared_memory(computed_value)
         if self.max_size is not None:
             self.ensure_capacity(_get_size_of_value(memoized_value))
-        self._map_values[key] = memoizable_value
+
+        try:
+            self._map_values[key] = memoizable_value
+        # Pickling may raise AttributeError in combination with multiprocessing
+        except AttributeError as exception:
+            # Fallback to returning computed value, but inform user about this failure
+            logging.exception(
+                "Could not store value for function %s.",
+                fully_qualified_function_name,
+                exc_info=exception,
+            )
+            return computed_value
 
         self._update_stats_on_miss(
             fully_qualified_function_name,

src/safeds_runner/memoization/_memoization_stats.py

@@ -40,7 +40,13 @@ def update_on_hit(self, access_timestamp: int, lookup_time: int) -> None:
         self.access_timestamps.append(access_timestamp)
         self.lookup_times.append(lookup_time)
 
-    def update_on_miss(self, access_timestamp: int, lookup_time: int, computation_time: int, memory_size: int) -> None:
+    def update_on_miss(
+        self,
+        access_timestamp: int,
+        lookup_time: int,
+        computation_time: int,
+        memory_size: int,
+    ) -> None:
         """
         Update the memoization stats on a cache miss.
 

src/safeds_runner/memoization/_memoization_utils.py

@@ -424,7 +424,11 @@ def _create_memoization_key(
         A memoization key, which contains the lists converted to tuples
     """
     arguments = [*positional_arguments, *keyword_arguments.values()]
-    return fully_qualified_function_name, _make_hashable(arguments), _make_hashable(hidden_arguments)
+    return (
+        fully_qualified_function_name,
+        _make_hashable(arguments),
+        _make_hashable(hidden_arguments),
+    )
 
 
 def _wrap_value_to_shared_memory(

src/safeds_runner/server/_json_encoder.py

@@ -49,6 +49,9 @@ def default(self, o: Any) -> Any:
             }
         elif isinstance(o, Image):
             # Send images together with their format, by default images are encoded only as PNG
-            return {"format": "png", "bytes": str(base64.encodebytes(o._repr_png_()), "utf-8")}
+            return {
+                "format": "png",
+                "bytes": str(base64.encodebytes(o._repr_png_()), "utf-8"),
+            }
         else:
             return json.JSONEncoder.default(self, o)

src/safeds_runner/server/_messages.py

@@ -233,7 +233,10 @@ def create_placeholder_value(placeholder_query: QueryMessageData, type_: str, va
 
     message: dict[str, Any] = {"name": placeholder_query.name, "type": type_}
     # Start Index >= 0
-    start_index = max(placeholder_query.window.begin if placeholder_query.window.begin is not None else 0, 0)
+    start_index = max(
+        placeholder_query.window.begin if placeholder_query.window.begin is not None else 0,
+        0,
+    )
     # Length >= 0
     length = max(placeholder_query.window.size, 0) if placeholder_query.window.size is not None else None
     if isinstance(value, safeds.data.labeled.containers.TabularDataset):
@@ -244,7 +247,11 @@ def create_placeholder_value(placeholder_query: QueryMessageData, type_: str, va
     ):
         max_index = value.number_of_rows
         value = value.slice_rows(start=start_index, length=length)
-        window_information: dict[str, int] = {"begin": start_index, "size": value.number_of_rows, "max": max_index}
+        window_information: dict[str, int] = {
+            "begin": start_index,
+            "size": value.number_of_rows,
+            "max": max_index,
+        }
         message["window"] = window_information
     message["value"] = value
     return message
@@ -281,7 +288,9 @@ def create_runtime_progress_done() -> str:
     return "done"
 
 
-def parse_validate_message(message: str) -> tuple[Message | None, str | None, str | None]:
+def parse_validate_message(
+    message: str,
+) -> tuple[Message | None, str | None, str | None]:
     """
     Validate the basic structure of a received message string and return a parsed message object.
 
@@ -300,14 +309,30 @@ def parse_validate_message(message: str) -> tuple[Message | None, str | None, st
     except json.JSONDecodeError:
         return None, f"Invalid message received: {message}", "Invalid Message: not JSON"
     if "type" not in message_dict:
-        return None, f"No message type specified in: {message}", "Invalid Message: no type"
+        return (
+            None,
+            f"No message type specified in: {message}",
+            "Invalid Message: no type",
+        )
     elif "id" not in message_dict:
         return None, f"No message id specified in: {message}", "Invalid Message: no id"
     elif "data" not in message_dict:
-        return None, f"No message data specified in: {message}", "Invalid Message: no data"
+        return (
+            None,
+            f"No message data specified in: {message}",
+            "Invalid Message: no data",
+        )
     elif not isinstance(message_dict["type"], str):
-        return None, f"Message type is not a string: {message}", "Invalid Message: invalid type"
+        return (
+            None,
+            f"Message type is not a string: {message}",
+            "Invalid Message: invalid type",
+        )
     elif not isinstance(message_dict["id"], str):
-        return None, f"Message id is not a string: {message}", "Invalid Message: invalid id"
+        return (
+            None,
+            f"Message id is not a string: {message}",
+            "Invalid Message: invalid id",
+        )
     else:
         return Message(**message_dict), None, None

src/safeds_runner/server/_pipeline_manager.py

@@ -151,7 +151,10 @@ def _send_message(self, message_type: str, value: dict[Any, Any] | str) -> None:
 
     def _send_exception(self, exception: BaseException) -> None:
         backtrace = get_backtrace_info(exception)
-        self._send_message(message_type_runtime_error, create_runtime_error_description(exception.__str__(), backtrace))
+        self._send_message(
+            message_type_runtime_error,
+            create_runtime_error_description(exception.__str__(), backtrace),
+        )
 
     def save_placeholder(self, placeholder_name: str, value: Any) -> None:
         """
@@ -177,7 +180,19 @@ def save_placeholder(self, placeholder_name: str, value: Any) -> None:
             and _has_explicit_identity_memory(value)
         ):
             value = ExplicitIdentityWrapper.existing(value)
-        self._placeholder_map[placeholder_name] = value
+
+        try:
+            self._placeholder_map[placeholder_name] = value
+        # Pickling may raise AttributeError in combination with multiprocessing
+        except AttributeError as exception:  # pragma: no cover
+            # Don't crash, but inform user about this failure
+            logging.exception(
+                "Could not store value for placeholder %s.",
+                placeholder_name,
+                exc_info=exception,
+            )
+            return
+
         self._send_message(
             message_type_placeholder_type,
             create_placeholder_description(placeholder_name, placeholder_type),

src/safeds_runner/server/_process_manager.py

@@ -40,7 +40,11 @@ def _message_queue(self) -> Queue[Message]:
 
     @cached_property
     def _message_queue_thread(self) -> threading.Thread:
-        return threading.Thread(daemon=True, target=self._consume_queue_messages, args=[asyncio.get_event_loop()])
+        return threading.Thread(
+            daemon=True,
+            target=self._consume_queue_messages,
+            args=[asyncio.get_event_loop()],
+        )
 
     @cached_property
     def _process_pool(self) -> ProcessPoolExecutor:
@@ -147,7 +151,7 @@ def _warmup_worker() -> None:
 
     from safeds.data.tabular.containers import Table  # pragma: no cover
 
-    Table({"a": [1]}).get_column("a").plot_histogram()  # pragma: no cover
+    Table({"a": [1]}).get_column("a").plot.histogram()  # pragma: no cover
 
 
 _State: TypeAlias = Literal["initial", "started", "shutdown"]