[Question about add-on development] How to use popup to display the details of exceptions in background task?

[L.M.Sherlock]

When the python code raises an exception in the main thread, a popup will show the details about the exception:

But when I move the task into background, the error will be silent. The progress bar gets stuck:

Are there any methods to use popup to display the details of exceptions in background task?

[abdo]

It appears you’re trying to call GUI code inside the background task (.setChecked). This can result in Anki hanging/crashing.

The currently recommended approach is to use CollectionOp/QueryOp to run background tasks. See Background Operations - Writing Anki Add-ons for an example. You can add a failure handler and call showWarning/tooltip inside it.

[L.M.Sherlock]

But I didn’t call GUI code. The popup of error is called by Anki itself.

[abdo]

I mean the menu_auto_disperse.setCheked line in your screenshot (If that’s called in the background). Can you post a code example?

[L.M.Sherlock]

The Error is just a example of popup. It is not the error happened in my background task.

[L.M.Sherlock]

For example, if I raise ValueException in the background task.

[L.M.Sherlock]

open-spaced-repetition/fsrs4anki-helper/blob/8abb058529fff1ca722325cf92b3a5979200fd23/reschedule.py#L277

What if fsrs.due_cnt_perday_from_first_day[due_before] raise a indexError?

[abdo]

My guess is that the progress dialog is getting stuck because mw.progress.finish() is not getting called when an exception occurs. I recommend removing the on_finish functions and putting the code in the on_done handler of mw.taskman.run_in_background() instead:

diff --git a/disperse_siblings.py b/disperse_siblings.py
index d6035a4..c52e1a4 100644
--- a/disperse_siblings.py
+++ b/disperse_siblings.py
@@ -76,7 +76,13 @@ def disperse(siblings):
     return best_due_dates
 
 def disperse_siblings(did, filter_flag=False, filtered_nid_string="", text_from_reschedule=""):
-    mw.taskman.run_in_background(lambda: disperse_siblings_backgroud(did, filter_flag, filtered_nid_string, text_from_reschedule))  
+    def on_done(future):
+        mw.progress.finish()
+        tooltip(future.result())
+        mw.col.reset()
+        mw.reset()
+
+    mw.taskman.run_in_background(lambda: disperse_siblings_backgroud(did, filter_flag, filtered_nid_string, text_from_reschedule), on_done)
 
 def disperse_siblings_backgroud(did, filter_flag=False, filtered_nid_string="", text_from_reschedule=""):
     custom_scheduler = check_fsrs4anki(mw.col.all_config())
@@ -126,13 +132,6 @@ def disperse_siblings_backgroud(did, filter_flag=False, filtered_nid_string="",

     finished_text = f"{text_from_reschedule +', ' if text_from_reschedule != '' else ''}{card_cnt} cards in {note_cnt} notes dispersed."

-    def on_finish():
-        tooltip(finished_text)
-        mw.progress.finish()
-        mw.col.reset()
-        mw.reset()
-
-    mw.taskman.run_on_main(on_finish)
     return finished_text

 # https://stackoverflow.com/questions/68180974/given-n-points-where-each-point-has-its-own-range-adjust-all-points-to-maximize      
diff --git a/reschedule.py b/reschedule.py
index ae91c9c..b12e908 100644
--- a/reschedule.py
+++ b/reschedule.py
@@ -101,17 +101,21 @@ class FSRS:
 def reschedule(did, recent=False, filter_flag=False, filtered_cids={}, filtered_nid_string=""):

     def on_done(future):
+        mw.progress.finish()
         tooltip(future.result())
+        mw.col.reset()
+        mw.reset()
+

     if filter_flag and len(filtered_cids) > 0:
-        fut = mw.taskman.run_in_background(lambda: reschedule_background(did, recent, filter_flag, filtered_cids))
+        fut = mw.taskman.run_in_background(lambda: reschedule_background(did, recent, filter_flag, filtered_cids), on_done)
         config = Config()
         config.load()
         if config.auto_disperse:
             text = fut.result()
             fut = mw.taskman.run_in_background(lambda: disperse_siblings_backgroud(did, filter_flag, filtered_nid_string, text_from_reschedule=text), on_done)
     else:
-        fut = mw.taskman.run_in_background(lambda: reschedule_background(did, recent, filter_flag, filtered_cids))
+        fut = mw.taskman.run_in_background(lambda: reschedule_background(did, recent, filter_flag, filtered_cids), on_done)

     return fut

@@ -287,11 +291,4 @@ def reschedule_background(did, recent=False, filter_flag=False, filtered_cids={}

     finished_text = f"{cnt} cards rescheduled"

-    def on_finish():
-        tooltip(finished_text)
-        mw.progress.finish()
-        mw.col.reset()
-        mw.reset()
-    
-    mw.taskman.run_on_main(on_finish)
     return finished_text

An important thing to notice is that mw.progress.finish() should be called before future.result() to ensure the progress dialog is proerly closed if an exception occurs.

[L.M.Sherlock]

Thank you very much!