Gen5: fix basculin-blue reckless ability handling

Closes #2058

so many spots needing updating:
- ability verifier (legality check)
- encounter template=>pk5 (generating)
- editor load abilities (show the ability in list)
- editor save ability (acknowledge ability index)

PKHeX.Core/Game/GameStrings/FilteredGameDataSource.cs

@@ -135,10 +135,18 @@ private static void LoadAbilityList(IPersonalAbility pi, Span<ComboItem> list, R
         for (int i = 0; i < list.Length; i++)
         {
             var value = pi.GetAbilityAtIndex(i);
-            var name = names[value];
             char suffix = i == 2 ? HiddenAbilitySuffix : (char)(AbilityIndexSuffix + i);
-            var display = $"{name} ({suffix})";
-            list[i] = new ComboItem(display, value);
+            var item = GetAbilityItem(names, value, suffix);
+            list[i] = item;
         }
     }
+
+    public static ComboItem GetAbilityItem(ReadOnlySpan<string> names, int value, char suffix)
+        => GetAbilityItem(names[value], suffix, value);
+
+    public static ComboItem GetAbilityItem(string name, char suffix, int value)
+    {
+        var display = $"{name} ({suffix})";
+        return new ComboItem(display, value);
+    }
 }

PKHeX.Core/Legality/Encounters/Generator/EncounterMutation.cs

@@ -83,6 +83,6 @@ public static EncounterMutation GetSuggested(EntityContext targetContext, byte l
             _ => false,
         },
         OnlyHidden => end.CanBeHidden() || mutation.HasFlag(CanAbilityPatch),
-        _ => false,
+        _ => true,
     };
 }

PKHeX.Core/Legality/Encounters/Templates/Gen5/EncounterEgg5.cs

@@ -77,6 +77,8 @@ public PK5 ConvertToPKM(ITrainerInfo tr, EncounterCriteria criteria)
         pk.PID = pid;
         pk.Gender = gender;
         pk.RefreshAbility(ability);
+        if (ability == 0 && this is { Species: (int)Core.Species.Basculin, Form: 1 })
+            pk.Ability = (int)Core.Ability.Reckless;
 
         return pk;
     }

PKHeX.Core/Legality/Encounters/Templates/Gen5/EncounterSlot5.cs

@@ -90,6 +90,8 @@ private void SetPINGA(PK5 pk, in EncounterCriteria criteria, PersonalInfo5B2W2 p
         var abilityIndex = Ability == AbilityPermission.OnlyHidden ? 2 : (int)((pk.PID >> 16) & 1);
         pk.RefreshAbility(abilityIndex);
         criteria.SetRandomIVs(pk);
+        if (abilityIndex == 0 && this is { Species: (int)Core.Species.Basculin, Form: 1, Version: GameVersion.B or GameVersion.W })
+            pk.Ability = (int)Core.Ability.Reckless;
     }
     #endregion
 

PKHeX.Core/Legality/Verifiers/Ability/AbilityVerifier.cs

@@ -30,6 +30,8 @@ private CheckResult VerifyAbility(LegalityAnalysis data)
         var pk = data.Entity;
         if (pk is PA9 pa9)
             return VerifyBirthAbility(data, pa9);
+        if (pk is PK5 pk5 && IsEdgeCaseBasculin(data, pk5, out var basc))
+            return basc;
 
         var abilities = (IPersonalAbility12)data.PersonalInfo;
 
@@ -95,6 +97,42 @@ private CheckResult VerifyAbility(LegalityAnalysis data)
         return VerifyAbility(data, abilities, abilIndex);
     }
 
+    private bool IsEdgeCaseBasculin(LegalityAnalysis data, PK5 pk5, out CheckResult result)
+    {
+        result = default;
+        // Gen5 Only Edge Case issue:
+        // - Basculin-Blue (form 1) *should* have Rock Head.
+        // In B/W, Blue-Striped Basculin have Reckless as its Ability (incorrect) due to referencing the wrong Personal Info.
+        // - However, the in-game trade Blue-Striped Basculin in White that has Rock Head (correct).
+        // In B2/W2, wild Blue-Striped Basculin have Rock Head (correct), but bred Blue-Striped Basculin have Reckless (incorrect).
+        // - When transferred to Pokémon Bank, any Blue-Striped Basculin with Reckless have their Ability changed to Rock Head (fixed).
+        // Impacted encounter types: Egg|Wild (B/W), Egg (B2/W2)
+
+        if (pk5 is not { Species: (int)Species.Basculin, Form: 1, HiddenAbility: false, Ability: not (int)Ability.Adaptability })
+            return false; // check abilities as usual.
+
+        var expect = (int)Ability.RockHead; // correct.
+        if (pk5.Version is GameVersion.B2 or GameVersion.W2)
+        {
+            var enc = data.EncounterMatch;
+            if (enc is EncounterEgg5)
+                expect = (int)Ability.Reckless; // incorrect
+        }
+        else if (pk5.Version is GameVersion.B or GameVersion.W)
+        {
+            var enc = data.EncounterMatch;
+            if (enc is not EncounterTrade5BW)
+                expect = (int)Ability.Reckless; // incorrect
+        }
+
+        var current = pk5.Ability;
+        if (current == expect)
+            result = VALID;
+        else
+            result = GetInvalid(AbilityUnexpected);
+        return true; // tell the analyzer to use this result
+    }
+
     public static bool IsValidAbilityBits(int bitNum) => bitNum is 1 or 2 or 4;
 
     private CheckResult VerifyAbility(LegalityAnalysis data, IPersonalAbility12 abilities, int abilIndex)

PKHeX.Core/PKM/PK5.cs

@@ -508,6 +508,13 @@ public PK6 ConvertToPK6()
         StringConverter345.TransferGlyphs56(pk6.NicknameTrash);
         StringConverter345.TransferString56(OriginalTrainerTrash, pk6.OriginalTrainerTrash);
 
+        // Fix Basculin-Blue
+        if (Species is (ushort)Core.Species.Basculin && Form == 1 && Ability == (int)Core.Ability.Reckless)
+        {
+            pk6.Ability = (int)Core.Ability.RockHead;
+            pk6.AbilityNumber = 1;
+        }
+
         // Fix Checksum
         pk6.RefreshChecksum();
 

PKHeX.WinForms/Controls/PKM Editor/EditPK5.cs

@@ -22,7 +22,7 @@ private void PopulateFieldsPK5()
         if (HaX)
             DEV_Ability.SelectedValue = pk5.Ability;
         else if (pk5.HiddenAbility)
-            CB_Ability.SelectedIndex = CB_Ability.Items.Count - 1;
+            CB_Ability.SelectedIndex = 2;
         else
             LoadAbility4(pk5);
 
@@ -45,7 +45,7 @@ private PK5 PreparePK5()
         pk5.PokeStarFame = (byte)NUD_PokeStarFame.Value;
         if (!HaX)
         {
-            pk5.HiddenAbility = CB_Ability.SelectedIndex is not (0 or 1);
+            pk5.HiddenAbility = CB_Ability.SelectedIndex is 2;
         }
         else
         {

PKHeX.WinForms/Controls/PKM Editor/LoadSave.cs

@@ -398,11 +398,16 @@ private void LoadAbility4(PKM pk)
     private static int GetAbilityIndex4(PKM pk)
     {
         var pi = pk.PersonalInfo;
-        int abilityIndex = pi.GetIndexOfAbility(pk.Ability);
-        if (abilityIndex < 0)
-            return 0;
+        var ability = pk.Ability;
+        int abilityIndex = pi.GetIndexOfAbility(ability);
         if (abilityIndex >= 2)
             return 2;
+        if (abilityIndex < 0)
+        {
+            if (ability == (int)Ability.Reckless && pk is { Context: EntityContext.Gen5, Species: (ushort)Species.Basculin, Form: 1 })
+                return 3; // manually appended "extra" bug case for Gen5 Basculin-Blue.
+            return 0; // fall back to first ability.
+        }
 
         var abils = (IPersonalAbility12)pi;
         if (abils.IsAbility12Same)

PKHeX.WinForms/Controls/PKM Editor/PKMEditor.cs

@@ -513,6 +513,8 @@ private void SetAbilityList()
         bool tmp = FieldsLoaded;
         FieldsLoaded = false;
         var items = GameInfo.FilteredSources.GetAbilityList(Entity.PersonalInfo);
+        if (Entity is { Context: EntityContext.Gen5, Species: (ushort)Species.Basculin, Form: 1 })
+            items = [..items, FilteredGameDataSource.GetAbilityItem(GameInfo.Strings.abilitylist, (int)Ability.Reckless, '*')];
         CB_Ability.DataSource = items;
         CB_Ability.SelectedIndex = Math.Clamp(ability, 0, items.Count - 1); // restore original index if available
         FieldsLoaded = tmp;