Abort request when PackageList gets deleted

This is a consequence of lazy loading and the re-loading we do when the Marketplace window gets closed. This solves a crash with reproduction steps:
1. Open the Marketplace.
2. Quickly close the Marketplace.
3. Quickly re-open the Marketplace.
4. The API responds to the request made by the first opening of the Marketplace.

This crashed because when the Marketplace first opened, it made a request to the API with the HttpRequestManager. This request takes a while to respond to. If you close and re-open the Marketplace, the PackageList gets destroyed and a new one gets made. The HttpRequestManager eventually gets a response and wants to call the callback of the first PackageList, but that one got destroyed in the Qt engine so it'll throw an error saying that the object doesn't exist any more.

Contributes to issue CURA-8557.

plugins/Marketplace/PackageList.py

@@ -2,6 +2,7 @@
 # Cura is released under the terms of the LGPLv3 or higher.
 
 from PyQt5.QtCore import pyqtProperty, pyqtSignal, pyqtSlot, Qt
+from PyQt5.QtNetwork import QNetworkReply
 from typing import Optional, TYPE_CHECKING
 
 from cura.CuraApplication import CuraApplication
@@ -9,7 +10,7 @@ from cura.UltimakerCloud.UltimakerCloudScope import UltimakerCloudScope  # To ma
 from UM.i18n import i18nCatalog
 from UM.Logger import Logger
 from UM.Qt.ListModel import ListModel
-from UM.TaskManagement.HttpRequestManager import HttpRequestManager  # To request the package list from the API.
+from UM.TaskManagement.HttpRequestManager import HttpRequestManager, HttpRequestData  # To request the package list from the API.
 from UM.TaskManagement.HttpRequestScope import JsonDecoratorScope  # To request JSON responses from the API.
 
 from . import Marketplace   # To get the list of packages. Imported this way to prevent circular imports.
@@ -17,7 +18,6 @@ from .PackageModel import PackageModel  # The contents of this list.
 
 if TYPE_CHECKING:
     from PyQt5.QtCore import QObject
-    from PyQt5.QtNetwork import QNetworkReply
 
 catalog = i18nCatalog("cura")
 
@@ -37,7 +37,7 @@ class PackageList(ListModel):
     def __init__(self, parent: "QObject" = None) -> None:
         super().__init__(parent)
 
-        self._is_loading = True
+        self._ongoing_request: Optional[HttpRequestData] = None
         self._scope = JsonDecoratorScope(UltimakerCloudScope(CuraApplication.getInstance()))
         self._error_message = ""
 
@@ -46,6 +46,13 @@ class PackageList(ListModel):
 
         self.addRoleName(self.PackageRole, "package")
 
+    def __del__(self) -> None:
+        """
+        When deleting this object, abort the request so that we don't get a callback from it later on a deleted C++
+        object.
+        """
+        self.abortRequest()
+
     @pyqtSlot()
     def request(self) -> None:
         """
@@ -53,16 +60,21 @@ class PackageList(ListModel):
 
         When the request is done, the list will get updated with the new package models.
         """
-        self.setIsLoading(True)
         self.setErrorMessage("")  # Clear any previous errors.
 
         http = HttpRequestManager.getInstance()
-        http.get(
+        self._ongoing_request = http.get(
             self._request_url,
             scope = self._scope,
             callback = self._parseResponse,
             error_callback = self._onError
         )
+        self.isLoadingChanged.emit()
+
+    @pyqtSlot()
+    def abortRequest(self) -> None:
+        HttpRequestManager.getInstance().abortRequest(self._ongoing_request)
+        self._ongoing_request = None
 
     def reset(self) -> None:
         self.clear()
@@ -70,18 +82,13 @@ class PackageList(ListModel):
 
     isLoadingChanged = pyqtSignal()
 
-    def setIsLoading(self, is_loading: bool) -> None:
-        if is_loading != self._is_loading:
-            self._is_loading = is_loading
-            self.isLoadingChanged.emit()
-
-    @pyqtProperty(bool, notify = isLoadingChanged, fset = setIsLoading)
+    @pyqtProperty(bool, notify = isLoadingChanged)
     def isLoading(self) -> bool:
         """
         Gives whether the list is currently loading the first page or loading more pages.
         :return: ``True`` if the list is downloading, or ``False`` if not downloading.
         """
-        return self._is_loading
+        return self._ongoing_request is not None
 
     hasMoreChanged = pyqtSignal()
 
@@ -155,13 +162,20 @@ class PackageList(ListModel):
 
         self._request_url = response_data["links"].get("next", "")  # Use empty string to signify that there is no next page.
         self.hasMoreChanged.emit()
-        self.setIsLoading(False)
+        self._ongoing_request = None
+        self.isLoadingChanged.emit()
 
-    def _onError(self, reply: "QNetworkReply", error: Optional["QNetworkReply.NetworkError"]) -> None:
+    def _onError(self, reply: "QNetworkReply", error: Optional[QNetworkReply.NetworkError]) -> None:
         """
         Handles networking and server errors when requesting the list of packages.
         :param reply: The reply with packages. This will most likely be incomplete and should be ignored.
         :param error: The error status of the request.
         """
-        Logger.error(f"Could not reach Marketplace server.")
+        if error == QNetworkReply.NetworkError.OperationCanceledError:
+            Logger.error("Cancelled request for packages.")
+            self._ongoing_request = None
+            return  # Don't show an error about this to the user.
+        Logger.error("Could not reach Marketplace server.")
         self.setErrorMessage(catalog.i18nc("@info:error", "Could not reach Marketplace."))
+        self._ongoing_request = None
+        self.isLoadingChanged.emit()