Made sure apportionment works with non-consecutive list/candidate numbers (#2807)

Author: Lionqueen94

backend/apportionment/src/candidate_nomination/mod.rs

@@ -3,13 +3,12 @@ mod structs;
 use tracing::{debug, info};
 
 use self::structs::{Candidate, ListCandidateNomination, PreferenceThreshold};
-pub use structs::CandidateNominationResult;
-
 use super::{
     ApportionmentError, ApportionmentInput, CandidateVotesTrait, ListVotesTrait,
     fraction::Fraction,
-    structs::{CandidateNominationInputType, CandidateNumber, LARGE_COUNCIL_THRESHOLD},
+    structs::{CandidateNominationInputType, CandidateNumber, LARGE_COUNCIL_THRESHOLD, ListNumber},
 };
+pub use structs::CandidateNominationResult;
 
 /// Candidate nomination
 pub(crate) fn candidate_nomination<'a, T: ApportionmentInput>(
@@ -97,12 +96,16 @@ fn candidate_nomination_per_list<'a, T: ListVotesTrait>(
     seats: u32,
     list_votes: &'a [T],
     preference_threshold: Fraction,
-    total_seats: &[u32],
+    total_seats: &[(ListNumber, u32)],
 ) -> Result<Vec<ListCandidateNomination<'a, T::Cv>>, ApportionmentError> {
     let mut list_candidate_nomination: Vec<ListCandidateNomination<T::Cv>> = vec![];
-    for (index, list) in list_votes.iter().enumerate() {
-        let list_seats = total_seats[index];
-        let candidate_votes = list.candidate_votes();
+    for list in list_votes {
+        let (list_number, list_seats) = total_seats
+            .iter()
+            .find(|(number, _)| *number == list.number())
+            .expect("Total seats exists")
+            .to_owned();
+        let candidate_votes = &list.candidate_votes();
         let candidate_votes_meeting_preference_threshold =
             candidate_votes_meeting_preference_threshold(preference_threshold, candidate_votes);
         let preferential_candidate_nomination = preferential_candidate_nomination::<T::Cv>(
@@ -142,8 +145,8 @@ fn candidate_nomination_per_list<'a, T: ListVotesTrait>(
                 }
             };
 
-        list_candidate_nomination.push(ListCandidateNomination::<T::Cv> {
-            list_number: list.number(),
+        list_candidate_nomination.push(ListCandidateNomination {
+            list_number,
             list_seats,
             preferential_candidate_nomination,
             other_candidate_nomination,
@@ -267,8 +270,10 @@ mod tests {
         structs::ListNumber,
         test_helpers::{
             ApportionmentInputMock, CandidateVotesMock,
+            candidate_nomination_fixture_with_given_list_numbers_and_number_of_seats,
             candidate_nomination_fixture_with_given_number_of_seats,
             seat_assignment_fixture_with_given_candidate_votes,
+            seat_assignment_fixture_with_given_list_numbers_candidate_numbers_and_votes,
         },
     };
 
@@ -341,6 +346,124 @@ mod tests {
         (chosen_candidates, not_chosen_candidates)
     }
 
+    /// Candidate nomination with non-consecutive list and candidate numbers
+    ///
+    /// List seats: [(1, 8), (2, 3), (4, 2), (5, 1), (7, 1)]  
+    /// List 1: Preferential candidate nominations of candidates 1, 4, 3, 5 and 12 and other candidate nominations of candidates 7, 8 and 9  
+    /// List 2: Preferential candidate nomination of candidate 2 and 6 and other candidate nomination of candidates 3  
+    /// List 3: Preferential candidate nomination of candidate 1 and 4 and no other candidate nominations  
+    /// List 4: Preferential candidate nomination of candidate 1 and no other candidate nominations  
+    /// List 5: Preferential candidate nomination of candidate 3 and no other candidate nominations
+    #[test]
+    fn test_with_lt_19_seats_and_non_consecutive_list_and_candidate_numbers() {
+        let quota = Fraction::new(5104, 15);
+        let seat_assignment_input =
+            seat_assignment_fixture_with_given_list_numbers_candidate_numbers_and_votes(
+                15,
+                vec![
+                    (
+                        1,
+                        vec![
+                            (1, 1069),
+                            (3, 303),
+                            (4, 321),
+                            (5, 210),
+                            (7, 36),
+                            (8, 101),
+                            (9, 79),
+                            (10, 121),
+                            (11, 150),
+                            (12, 181),
+                        ],
+                    ),
+                    (2, vec![(2, 452), (3, 39), (4, 81), (6, 274), (7, 131)]),
+                    (4, vec![(1, 229), (2, 147), (4, 191)]),
+                    (5, vec![(1, 347), (3, 189)]),
+                    (7, vec![(3, 266), (2, 187)]),
+                ],
+            );
+        let input = candidate_nomination_fixture_with_given_list_numbers_and_number_of_seats(
+            quota,
+            &seat_assignment_input,
+            vec![(1, 8), (2, 3), (4, 2), (5, 1), (7, 1)],
+        );
+        let result = candidate_nomination::<ApportionmentInputMock>(&input).unwrap();
+
+        assert_eq!(result.preference_threshold.percentage, 50);
+        assert_eq!(
+            result.preference_threshold.number_of_votes,
+            quota * Fraction::new(result.preference_threshold.percentage, 100)
+        );
+        check_list_candidate_nomination(
+            &result.list_candidate_nomination[0],
+            &[1, 4, 3, 5, 12],
+            &[7, 8, 9],
+            &[1, 4, 3, 5, 12, 7, 8, 9, 10, 11],
+        );
+        check_list_candidate_nomination(
+            &result.list_candidate_nomination[1],
+            &[2, 6],
+            &[3],
+            &[2, 6, 3, 4, 7],
+        );
+        check_list_candidate_nomination(
+            &result.list_candidate_nomination[2],
+            &[1, 4],
+            &[],
+            &[1, 4, 2],
+        );
+        check_list_candidate_nomination(&result.list_candidate_nomination[3], &[1], &[], &[]);
+        check_list_candidate_nomination(&result.list_candidate_nomination[4], &[3], &[], &[]);
+
+        let lists = input.list_votes;
+        check_chosen_candidates(
+            &result.chosen_candidates,
+            &lists[0].number,
+            &[
+                &lists[0].candidate_votes[..7],
+                &lists[0].candidate_votes[10..],
+            ]
+            .concat(),
+            &lists[0].candidate_votes[8..9],
+        );
+        check_chosen_candidates(
+            &result.chosen_candidates,
+            &lists[1].number,
+            &[
+                &lists[1].candidate_votes[..2],
+                &lists[1].candidate_votes[3..4],
+            ]
+            .concat(),
+            &[
+                &lists[1].candidate_votes[2..3],
+                &lists[1].candidate_votes[4..],
+            ]
+            .concat(),
+        );
+        check_chosen_candidates(
+            &result.chosen_candidates,
+            &lists[2].number,
+            &[
+                &lists[2].candidate_votes[..1],
+                &lists[2].candidate_votes[2..],
+            ]
+            .concat(),
+            &lists[2].candidate_votes[1..2],
+        );
+        check_chosen_candidates(
+            &result.chosen_candidates,
+            &lists[3].number,
+            &lists[3].candidate_votes[..1],
+            &lists[3].candidate_votes[2..],
+        );
+        check_chosen_candidates(
+            &result.chosen_candidates,
+            &lists[4].number,
+            &lists[4].candidate_votes[..1],
+            &lists[4].candidate_votes[2..],
+        );
+    }
+
     /// Candidate nomination with ranking change due to preferential candidate nomination
     ///
     /// Actual case from GR2022  

backend/apportionment/src/lib.rs

@@ -14,8 +14,8 @@ pub use self::{
 };
 use self::{
     candidate_nomination::candidate_nomination,
-    seat_assignment::seat_assignment,
-    structs::{ApportionmentOutput, as_candidate_nomination_input},
+    seat_assignment::{as_candidate_nomination_input, seat_assignment},
+    structs::ApportionmentOutput,
 };
 
 pub fn process<T: ApportionmentInput>(