normal note types now generate a dummy card if required

In the cloze deletion case, we already created a dummy card 0 when
no cloze deletions were found. This change makes normal note types
behave the same way - if no cards would be generated, a dummy card
0 is added to allow the note to be added.

This also applies when modifying note types - it is now possible
to delete card templates even if some notes only use that template,
as a dummy card 0 will be generated for notes that end up with no
cards left.

rslib/src/backend/mod.rs

@@ -78,7 +78,6 @@ fn anki_error_to_proto_error(err: AnkiError, i18n: &I18n) -> pb::BackendError {
         AnkiError::SchemaChange => V::InvalidInput(pb::Empty {}),
         AnkiError::JSONError { info } => V::JsonError(info),
         AnkiError::ProtoError { info } => V::ProtoError(info),
-        AnkiError::NoCardsGenerated => todo!(),
     };
 
     pb::BackendError {

rslib/src/err.rs

@@ -48,9 +48,6 @@ pub enum AnkiError {
 
     #[fail(display = "Operation modifies schema, but schema not marked modified.")]
     SchemaChange,
-
-    #[fail(display = "No cards generated.")]
-    NoCardsGenerated,
 }
 
 // error helpers

rslib/src/notes.rs

@@ -142,13 +142,8 @@ impl Collection {
 
     pub(crate) fn add_note_inner(&mut self, ctx: &CardGenContext, note: &mut Note) -> Result<()> {
         note.prepare_for_update(&ctx.notetype, ctx.usn)?;
-        let cards = ctx.new_cards_required(note, Default::default());
-        if cards.is_empty() {
-            return Err(AnkiError::NoCardsGenerated);
-        }
-        // add note first, as we need the allocated ID for the cards
         self.storage.add_note(note)?;
-        self.add_generated_cards(ctx, note.id, &cards)
+        self.generate_cards_for_new_note(ctx, note)
     }
 
     pub fn update_note(&mut self, note: &mut Note) -> Result<()> {
@@ -177,12 +172,7 @@ impl Collection {
 #[cfg(test)]
 mod test {
     use super::{anki_base91, field_checksum};
-    use crate::{
-        collection::open_test_collection,
-        decks::DeckID,
-        err::{AnkiError, Result},
-        search::SortMode,
-    };
+    use crate::{collection::open_test_collection, decks::DeckID, err::Result};
 
     #[test]
     fn test_base91() {
@@ -200,35 +190,43 @@ mod test {
     }
 
     #[test]
-    fn adding() -> Result<()> {
+    fn adding_cards() -> Result<()> {
         let mut col = open_test_collection();
-        let nt = col.get_notetype_by_name("basic")?.unwrap();
+        let nt = col
+            .get_notetype_by_name("basic (and reversed card)")?
+            .unwrap();
 
         let mut note = nt.new_note();
-        assert_eq!(col.add_note(&mut note), Err(AnkiError::NoCardsGenerated));
-
-        note.fields[1] = "foo".into();
-        assert_eq!(col.add_note(&mut note), Err(AnkiError::NoCardsGenerated));
-
-        note.fields[0] = "bar".into();
+        // if no cards are generated, 1 card is added
         col.add_note(&mut note).unwrap();
+        let existing = col.storage.existing_cards_for_note(note.id)?;
+        assert_eq!(existing.len(), 1);
+        assert_eq!(existing[0].ord, 0);
 
-        assert_eq!(
-            col.search_cards(&format!("nid:{}", note.id), SortMode::NoOrder)
-                .unwrap()
-                .len(),
-            1
-        );
+        // nothing changes if the first field is filled
+        note.fields[0] = "test".into();
+        col.update_note(&mut note).unwrap();
+        let existing = col.storage.existing_cards_for_note(note.id)?;
+        assert_eq!(existing.len(), 1);
+        assert_eq!(existing[0].ord, 0);
 
+        // second field causes another card to be generated
+        note.fields[1] = "test".into();
+        col.update_note(&mut note).unwrap();
+        let existing = col.storage.existing_cards_for_note(note.id)?;
+        assert_eq!(existing.len(), 2);
+        assert_eq!(existing[1].ord, 1);
+
+        // cloze cards also generate card 0 if no clozes are found
         let nt = col.get_notetype_by_name("cloze")?.unwrap();
         let mut note = nt.new_note();
-        // cloze cards without any cloze deletions are allowed
         col.add_note(&mut note).unwrap();
         let existing = col.storage.existing_cards_for_note(note.id)?;
         assert_eq!(existing.len(), 1);
         assert_eq!(existing[0].ord, 0);
         assert_eq!(existing[0].original_deck_id, DeckID(1));
 
+        // and generate cards for any cloze deletions
         note.fields[0] = "{{c1::foo}} {{c2::bar}} {{c3::baz}} {{c0::quux}} {{c501::over}}".into();
         col.update_note(&mut note)?;
         let existing = col.storage.existing_cards_for_note(note.id)?;

rslib/src/notetype/cardgen.rs

@@ -86,9 +86,20 @@ impl CardGenContext<'_> {
         existing: &[AlreadyGeneratedCardInfo],
     ) -> Vec<CardToGenerate> {
         let extracted = extract_data_from_existing_cards(existing);
-        match self.notetype.config.kind() {
+        let cards = match self.notetype.config.kind() {
             NoteTypeKind::Normal => self.new_cards_required_normal(note, &extracted),
             NoteTypeKind::Cloze => self.new_cards_required_cloze(note, &extracted),
+        };
+        if extracted.existing_ords.is_empty() && cards.is_empty() {
+            // if there are no existing cards and no cards will be generated,
+            // we add card 0 to ensure the note always has at least one card
+            vec![CardToGenerate {
+                ord: 0,
+                did: extracted.deck_id,
+                due: extracted.due,
+            }]
+        } else {
+            cards
         }
     }
 
@@ -128,8 +139,7 @@ impl CardGenContext<'_> {
         for field in note.fields() {
             add_cloze_numbers_in_string(field, &mut set);
         }
-        let cards: Vec<_> = set
-            .into_iter()
+        set.into_iter()
             .filter_map(|cloze_ord| {
                 let card_ord = cloze_ord.saturating_sub(1).min(499);
                 if extracted.existing_ords.contains(&(card_ord as u32)) {
@@ -142,17 +152,7 @@ impl CardGenContext<'_> {
                     })
                 }
             })
-            .collect();
-        if cards.is_empty() && extracted.existing_ords.is_empty() {
-            // if no cloze deletions are found, we add a card with ord 0
-            vec![CardToGenerate {
-                ord: 0,
-                did: extracted.deck_id,
-                due: extracted.due,
-            }]
-        } else {
-            cards
-        }
+            .collect()
     }
 }
 
@@ -200,12 +200,33 @@ pub(crate) fn extract_data_from_existing_cards(
 }
 
 impl Collection {
+    pub(crate) fn generate_cards_for_new_note(
+        &mut self,
+        ctx: &CardGenContext,
+        note: &Note,
+    ) -> Result<()> {
+        self.generate_cards_for_note(ctx, note, false)
+    }
+
     pub(crate) fn generate_cards_for_existing_note(
         &mut self,
         ctx: &CardGenContext,
         note: &Note,
     ) -> Result<()> {
-        let existing = self.storage.existing_cards_for_note(note.id)?;
+        self.generate_cards_for_note(ctx, note, true)
+    }
+
+    fn generate_cards_for_note(
+        &mut self,
+        ctx: &CardGenContext,
+        note: &Note,
+        check_existing: bool,
+    ) -> Result<()> {
+        let existing = if check_existing {
+            self.storage.existing_cards_for_note(note.id)?
+        } else {
+            vec![]
+        };
         let cards = ctx.new_cards_required(note, &existing);
         if cards.is_empty() {
             return Ok(());
@@ -225,7 +246,7 @@ impl Collection {
                 continue;
             }
             let note = self.storage.get_note(nid)?.unwrap();
-            self.generate_cards_for_existing_note(ctx, &note)?;
+            self.generate_cards_for_note(ctx, &note, true)?;
         }
 
         Ok(())

rslib/src/notetype/mod.rs

@@ -166,12 +166,19 @@ impl NoteType {
         self.templates.push(CardTemplate::new(name, qfmt, afmt));
     }
 
-    pub(crate) fn prepare_for_adding(&mut self) {
+    pub(crate) fn prepare_for_adding(&mut self) -> Result<()> {
         // defaults to 0
         self.config.target_deck_id = 1;
+        if self.fields.is_empty() {
+            return Err(AnkiError::invalid_input("1 field required"));
+        }
+        if self.templates.is_empty() {
+            return Err(AnkiError::invalid_input("1 template required"));
+        }
         self.normalize_names();
         self.ensure_names_unique();
         self.update_requirements();
+        Ok(())
     }
 
     pub fn new_note(&self) -> Note {

rslib/src/notetype/schemachange.rs

@@ -240,5 +240,4 @@ mod test {
     }
 }
 
-
 // fixme: make sure we don't orphan notes

rslib/src/notetype/stock.rs

@@ -58,7 +58,7 @@ pub(crate) fn basic(i18n: &I18n) -> NoteType {
             fieldref(back),
         ),
     );
-    nt.prepare_for_adding();
+    nt.prepare_for_adding().unwrap();
     nt
 }
 
@@ -74,7 +74,7 @@ pub(crate) fn basic_typing(i18n: &I18n) -> NoteType {
         fieldref(front),
         back
     );
-    nt.prepare_for_adding();
+    nt.prepare_for_adding().unwrap();
     nt
 }
 
@@ -92,7 +92,7 @@ pub(crate) fn basic_forward_reverse(i18n: &I18n) -> NoteType {
             fieldref(front),
         ),
     );
-    nt.prepare_for_adding();
+    nt.prepare_for_adding().unwrap();
     nt
 }
 
@@ -103,7 +103,7 @@ pub(crate) fn basic_optional_reverse(i18n: &I18n) -> NoteType {
     nt.add_field(addrev.as_ref());
     let tmpl = &mut nt.templates[1].config;
     tmpl.q_format = format!("{{{{#{}}}}}{}{{{{/{}}}}}", addrev, tmpl.q_format, addrev);
-    nt.prepare_for_adding();
+    nt.prepare_for_adding().unwrap();
     nt
 }
 
@@ -124,6 +124,6 @@ pub(crate) fn cloze(i18n: &I18n) -> NoteType {
  color: lightblue;
 }
 ";
-    nt.prepare_for_adding();
+    nt.prepare_for_adding().unwrap();
     nt
 }