Report error explicitly if card activities file is empty

core/card/card_activity_deserializer.go

@@ -2,6 +2,7 @@ package card
 
 import (
 	"bytes"
+	"fmt"
 	"time"
 
 	"github.com/gottenheim/ariadne/libraries/config"
@@ -11,7 +12,7 @@ func DeserializeCardActivityChain(activitiesBinary []byte) (CardActivity, error)
 	cfg, err := config.FromYamlReader(bytes.NewReader(activitiesBinary))
 
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("Failed to read card activities: %v", err)
 	}
 
 	cardActivitiesModel := &CardActivitiesModel{}

details/fs_repo/answered_card_emitter.go

@@ -2,6 +2,7 @@ package fs_repo
 
 import (
 	"context"
+	"fmt"
 	"io"
 	"os"
 	"path/filepath"
@@ -48,7 +49,7 @@ func (e *fileCardEmitter) Run(ctx context.Context, output chan<- card.BriefCard)
 		cardActivities, err := e.cardRepo.ReadCardActivities(cardDir)
 
 		if err != nil {
-			return err
+			return fmt.Errorf("failed to read activities for card %v", cardDir)
 		}
 
 		section, entry := e.cardRepo.GetCardPathSection(cardDir), e.cardRepo.GetCardPathEntry(cardDir)

use_cases/study_cards_session.go

@@ -24,7 +24,5 @@ func NewStudyCardsSession(timeSource datetime.TimeSource, cardRepo card.CardRepo
 func (s *StudyCardsSession) Run(cardEmitter pipeline.Emitter[card.BriefCard], config *study.DailyCardsConfig) error {
 	session := study.NewSession(s.timeSource, s.cardRepo, s.userInteractor)
 
-	session.Run(config, cardEmitter)
-
-	return nil
+	return session.Run(config, cardEmitter)
 }