Defiant works, but self inflicted stat changes still proc the stat raise.

src/data/ability.ts

@@ -81,6 +81,7 @@ type AbAttrCondition = (pokemon: Pokemon) => boolean;
 
 type PokemonAttackCondition = (user: Pokemon, target: Pokemon, move: Move) => boolean;
 type PokemonDefendCondition = (target: Pokemon, user: Pokemon, move: Move) => boolean;
+type PokemonStatChangeCondition = (target: Pokemon, statsChanged: BattleStat[], levels: integer) => boolean;
 
 export abstract class AbAttr {
   public showAbility: boolean;
@@ -384,6 +385,12 @@ export class PostDefendAbAttr extends AbAttr {
   }
 }
 
+export class PostStatChangeAbAttr extends AbAttr {
+  applyPostStatChange(pokemon: Pokemon, statsChanged: BattleStat[], levelChanged: integer, args: any[]): boolean | Promise<boolean> {
+    return false;
+  }
+}
+
 export class MoveImmunityAbAttr extends PreDefendAbAttr {
   private immuneCondition: PreDefendAbAttrCondition;
 
@@ -613,6 +620,29 @@ export class PostDefendAbilityGiveAbAttr extends PostDefendAbAttr {
   }
 }
 
+export class PostStatChangeStatChangeAbAttr extends PostStatChangeAbAttr {
+  private condition: PokemonStatChangeCondition;
+  private statsToChange: BattleStat[];
+  private levels: integer;
+
+  constructor(condition: PokemonStatChangeCondition, statsToChange: BattleStat[], levels: integer) {
+    super(true);
+
+    this.condition = condition;
+    this.statsToChange = statsToChange;
+    this.levels = levels;
+  }
+
+  applyPostStatChange(pokemon: Pokemon, statsChanged: BattleStat[], levelsChanged: integer, args: any[]): boolean {
+    if (this.condition(pokemon, statsChanged, levelsChanged)) {
+      pokemon.scene.unshiftPhase(new StatChangePhase(pokemon.scene, (pokemon).getBattlerIndex(), true, this.statsToChange, this.levels));
+      return true;
+    }
+
+    return false;
+  }
+}
+
 export class PreAttackAbAttr extends AbAttr {
   applyPreAttack(pokemon: Pokemon, passive: boolean, defender: Pokemon, move: PokemonMove, args: any[]): boolean | Promise<boolean> {
     return false;
@@ -2002,6 +2032,11 @@ export function applyPreStatChangeAbAttrs(attrType: { new(...args: any[]): PreSt
   return applyAbAttrsInternal<PreStatChangeAbAttr>(attrType, pokemon, (attr, passive) => attr.applyPreStatChange(pokemon, passive, stat, cancelled, args), args);
 }
 
+export function applyPostStatChangeAbAttrs(attrType: { new(...args: any[]): PostStatChangeAbAttr },
+  pokemon: Pokemon, stats: BattleStat[], levels: integer, ...args: any[]): Promise<void> {
+  return applyAbAttrsInternal<PostStatChangeAbAttr>(attrType, pokemon, (attr, passive) => attr.applyPostStatChange(pokemon, stats, levels, args), args);
+}
+
 export function applyPreSetStatusAbAttrs(attrType: { new(...args: any[]): PreSetStatusAbAttr },
   pokemon: Pokemon, effect: StatusEffect, cancelled: Utils.BooleanHolder, ...args: any[]): Promise<void> {
   const simulated = args.length > 1 && args[1];
@@ -2379,7 +2414,8 @@ export function initAbilities() {
       .ignorable(),
     new Ability(Abilities.UNNERVE, "Unnerve", "Unnerves opposing Pokémon and makes them unable to eat Berries.", 5)
       .attr(PreventBerryUseAbAttr),
-    new Ability(Abilities.DEFIANT, "Defiant (N)", "Boosts the Pokémon's Attack stat sharply when its stats are lowered.", 5),
+    new Ability(Abilities.DEFIANT, "Defiant", "Boosts the Pokémon's Attack stat sharply when its stats are lowered.", 5)
+      .attr(PostStatChangeStatChangeAbAttr, (target, statsChanged, levels) => levels < 0, [BattleStat.ATK], 2),
     new Ability(Abilities.DEFEATIST, "Defeatist", "Halves the Pokémon's Attack and Sp. Atk stats when its HP becomes half or less.", 5)
       .attr(BattleStatMultiplierAbAttr, BattleStat.ATK, 0.5)
       .attr(BattleStatMultiplierAbAttr, BattleStat.SPATK, 0.5)

src/phases.ts

@@ -30,7 +30,7 @@ import { Weather, WeatherType, getRandomWeatherType, getTerrainBlockMessage, get
 import { TempBattleStat } from "./data/temp-battle-stat";
 import { ArenaTagSide, ArenaTrapTag, MistTag, TrickRoomTag } from "./data/arena-tag";
 import { ArenaTagType } from "./data/enums/arena-tag-type";
-import { CheckTrappedAbAttr, MoveAbilityBypassAbAttr, IgnoreOpponentStatChangesAbAttr, PostAttackAbAttr, PostBattleAbAttr, PostDefendAbAttr, PostSummonAbAttr, PostTurnAbAttr, PostWeatherLapseAbAttr, PreSwitchOutAbAttr, PreWeatherDamageAbAttr, ProtectStatAbAttr, RedirectMoveAbAttr, RunSuccessAbAttr, StatChangeMultiplierAbAttr, SuppressWeatherEffectAbAttr, SyncEncounterNatureAbAttr, applyAbAttrs, applyCheckTrappedAbAttrs, applyPostAttackAbAttrs, applyPostBattleAbAttrs, applyPostDefendAbAttrs, applyPostSummonAbAttrs, applyPostTurnAbAttrs, applyPostWeatherLapseAbAttrs, applyPreStatChangeAbAttrs, applyPreSwitchOutAbAttrs, applyPreWeatherEffectAbAttrs, BattleStatMultiplierAbAttr, applyBattleStatMultiplierAbAttrs, IncrementMovePriorityAbAttr, applyPostVictoryAbAttrs, PostVictoryAbAttr, applyPostBattleInitAbAttrs, PostBattleInitAbAttr, BlockNonDirectDamageAbAttr as BlockNonDirectDamageAbAttr, applyPostKnockOutAbAttrs, PostKnockOutAbAttr, PostBiomeChangeAbAttr, applyPostFaintAbAttrs, PostFaintAbAttr, IncreasePpAbAttr } from "./data/ability";
+import { CheckTrappedAbAttr, MoveAbilityBypassAbAttr, IgnoreOpponentStatChangesAbAttr, PostAttackAbAttr, PostBattleAbAttr, PostDefendAbAttr, PostSummonAbAttr, PostTurnAbAttr, PostWeatherLapseAbAttr, PreSwitchOutAbAttr, PreWeatherDamageAbAttr, ProtectStatAbAttr, RedirectMoveAbAttr, RunSuccessAbAttr, StatChangeMultiplierAbAttr, SuppressWeatherEffectAbAttr, SyncEncounterNatureAbAttr, applyAbAttrs, applyCheckTrappedAbAttrs, applyPostAttackAbAttrs, applyPostBattleAbAttrs, applyPostDefendAbAttrs, applyPostSummonAbAttrs, applyPostTurnAbAttrs, applyPostWeatherLapseAbAttrs, applyPreStatChangeAbAttrs, applyPreSwitchOutAbAttrs, applyPreWeatherEffectAbAttrs, BattleStatMultiplierAbAttr, applyBattleStatMultiplierAbAttrs, IncrementMovePriorityAbAttr, applyPostVictoryAbAttrs, PostVictoryAbAttr, applyPostBattleInitAbAttrs, PostBattleInitAbAttr, BlockNonDirectDamageAbAttr as BlockNonDirectDamageAbAttr, applyPostKnockOutAbAttrs, PostKnockOutAbAttr, PostBiomeChangeAbAttr, applyPostFaintAbAttrs, PostFaintAbAttr, IncreasePpAbAttr, PostStatChangeAbAttr, applyPostStatChangeAbAttrs } from "./data/ability";
 import { Abilities } from "./data/enums/abilities";
 import { Unlockables, getUnlockableName } from "./system/unlockables";
 import { getBiomeKey } from "./field/arena";
@@ -2632,6 +2632,7 @@ export class StatChangePhase extends PokemonPhase {
       for (let stat of filteredStats)
         pokemon.summonData.battleStats[stat] = Math.max(Math.min(pokemon.summonData.battleStats[stat] + levels.value, 6), -6);
       
+      applyPostStatChangeAbAttrs(PostStatChangeAbAttr, pokemon, filteredStats, this.levels)
       this.end();
     };