[processing] Don't hold on to algorithm instances for menu items

nyalldawson · nyalldawson · commit 1d62d106fbfa · 2018-05-31T15:28:12.000+10:00
Instead, only store references to the algorithm id string, and use this to retrieve algorithms when the actions are triggered. This avoids errors caused by the algorithm instances being removed, e.g. due to plugin removal or reload of providers (e.g. by opening options dialog). Fixes #19070
diff --git a/python/plugins/processing/gui/menus.py b/python/plugins/processing/gui/menus.py
@@ -189,9 +189,10 @@ def addAlgorithmEntry(alg, menuName, submenuName, actionText=None, icon=None, ad
             alg_title = QgsStringUtils.capitalize(alg.displayName(), QgsStringUtils.TitleCase)
         actionText = alg_title + QCoreApplication.translate('Processing', '…')
     action = QAction(icon or alg.icon(), actionText, iface.mainWindow())
-    action.setData(alg.id())
-    action.triggered.connect(lambda: _executeAlgorithm(alg))
-    action.setObjectName("mProcessingUserMenu_%s" % alg.id())
+    alg_id = alg.id()
+    action.setData(alg_id)
+    action.triggered.connect(lambda: _executeAlgorithm(alg_id))
+    action.setObjectName("mProcessingUserMenu_%s" % alg_id)
 
     if menuName:
         menu = getMenu(menuName, iface.mainWindow().menuBar())
@@ -225,11 +226,20 @@ def removeAlgorithmEntry(alg, menuName, submenuName, delButton=True):
                 algorithmsToolbar.removeAction(action)
 
 
-def _executeAlgorithm(alg):
+def _executeAlgorithm(alg_id):
+    alg = QgsApplication.processingRegistry().createAlgorithmById(alg_id)
+    if alg is None:
+        dlg = MessageDialog()
+        dlg.setTitle(Processing.tr('Missing Algorithm'))
+        dlg.setMessage(
+            Processing.tr('The algorithm "{}" is no longer available. (Perhaps a plugin was uninstalled?)').format(alg_id))
+        dlg.exec_()
+        return
+
     ok, message = alg.canExecute()
     if not ok:
         dlg = MessageDialog()
-        dlg.setTitle(Processing.tr('Missing dependency'))
+        dlg.setTitle(Processing.tr('Missing Dependency'))
         dlg.setMessage(
             Processing.tr('<h3>Missing dependency. This algorithm cannot '
                           'be run :-( </h3>\n{0}').format(message))
