per-fact empty card deletion, and delete hook

anki/collection.py

@@ -391,6 +391,10 @@ select id from notes where id in %s and id not in (select nid from cards)""" %
                      ids2str(nids))
         self._remNotes(nids)
 
+    def remEmptyCards(self, ids):
+        if runFilter("remEmptyCards", len(ids), True):
+            self.remCards(ids)
+
     # Field checksums and sorting fields
     ##########################################################################
 

anki/models.py

@@ -348,7 +348,7 @@ select id from notes where mid = ?)""" % " ".join(map),
 
     def _syncTemplates(self, m):
         rem = self.col.genCards(self.nids(m))
-        self.col.remCards(rem)
+        self.col.remEmptyCards(rem)
 
     # Model changing
     ##########################################################################

anki/notes.py

@@ -157,4 +157,5 @@ insert or replace into notes values (?,?,?,?,?,?,?,?,?,?,?,?)""",
     def _postFlush(self):
         # generate missing cards
         if not self.newlyAdded:
-            self.col.genCards([self.id])
+            ids = self.col.genCards([self.id])
+            self.col.remEmptyCards(ids)

tests/test_cards.py

@@ -5,6 +5,7 @@ from anki.db import DB
 from anki.consts import *
 from anki.utils import hexifyID
 from tests.shared import getEmptyDeck
+from anki.hooks import addHook, remHook
 
 def test_previewCards():
     deck = getEmptyDeck()
@@ -75,6 +76,18 @@ def test_genrem():
     mm.save(m, templates=True)
     assert len(f.cards()) == 1
     # if we add to the note, a card should be automatically generated
+    f.load()
     f['Back'] = "1"
     f.flush()
     assert len(f.cards()) == 2
+    # deleteion calls a hook to let the user abort the delete. let's abort it:
+    def abort(val, *args):
+        return False
+    addHook("remEmptyCards", abort)
+    f['Back'] = ""
+    f.flush()
+    assert len(f.cards()) == 2
+    # if there's no filter, or it returns true, the cards get deleted
+    remHook("remEmptyCards", abort)
+    f.flush()
+    assert len(f.cards()) == 1