error if same person selected as cox + rower

src/model/logbook.rs

@@ -76,6 +76,7 @@ pub enum LogbookCreateError {
     ShipmasterAlreadyOnWater,
     RowerAlreadyOnWater(User),
     RowerCreateError(i64, String),
+    SamePersonShipmasterAndRower,
 }
 
 impl Logbook {
@@ -196,6 +197,10 @@ ORDER BY departure DESC
 
         for rower in &log.rowers {
             let user = User::find_by_id(db, *rower as i32).await.unwrap();
+            if *rower == log.shipmaster {
+                return Err(LogbookCreateError::SamePersonShipmasterAndRower);
+            }
+
             if user.on_water(db).await {
                 return Err(LogbookCreateError::RowerAlreadyOnWater(user));
             }
@@ -487,6 +492,30 @@ mod test {
         assert_eq!(res, Err(LogbookCreateError::ShipmasterAlreadyOnWater));
     }
 
+    #[sqlx::test]
+    fn test_create_same_person_cox_and_rower() {
+        let pool = testdb!();
+
+        let res = Logbook::create(
+            &pool,
+            LogToAdd {
+                boat_id: 3,
+                shipmaster: 5,
+                shipmaster_only_steering: false,
+                departure: "2128-05-20T12:00".into(),
+                arrival: None,
+                destination: None,
+                distance_in_km: None,
+                comments: None,
+                logtype: None,
+                rowers: vec![5],
+            },
+        )
+        .await;
+
+        assert_eq!(res, Err(LogbookCreateError::SamePersonShipmasterAndRower));
+    }
+
     #[sqlx::test]
     fn test_create_too_many_rowers() {
         let pool = testdb!();