fix csv update, avoid existing file with empty file

Signed-off-by: r2k1 <yokree@gmail.com>

pkg/costmodel/csv_export.go

@@ -96,18 +96,18 @@ func (e *csvExporter) Update(ctx context.Context) error {
 }
 
 func (e *csvExporter) updateExportCSV(ctx context.Context, previousExportTmp *os.File, allocationDates map[time.Time]struct{}, result *os.File) error {
-	csvDates, err := e.loadDates(previousExportTmp)
+	previousDates, err := e.loadDates(previousExportTmp)
 	if err != nil {
 		return err
 	}
 
-	for date := range csvDates {
+	for date := range previousDates {
 		delete(allocationDates, date)
 	}
 
 	if len(allocationDates) == 0 {
 		log.Info("export file in cloud storage already contain data for all dates, skipping update")
-		return nil
+		return errNoData
 	}
 
 	newExportTmp, err := os.CreateTemp("", "opencost-new-export-*.csv")

pkg/costmodel/csv_export_test.go

@@ -121,7 +121,7 @@ func Test_UpdateCSV(t *testing.T) {
 			},
 		}
 		err := UpdateCSV(context.TODO(), storage, model)
-		require.NoError(t, err)
+		require.Equal(t, err, errNoData)
 		assert.Equal(t, string(storage.Data), data)
 		assert.Len(t, model.ComputeAllocationCalls(), 0)
 	})