[Hotfix] Abilities that prevent ATK drops no longer stop other stat drops (#3624)

* Abilities that prevent ATK drops no longer stop other stat drops

* Apply suggestions from code review

Co-authored-by: Mumble <kimjoanne@protonmail.com>

* Add `isNullOrUndefined()` utility function

---------

src/data/ability.ts

@@ -2395,16 +2395,16 @@ export class PreStatChangeAbAttr extends AbAttr {
 }
 
 export class ProtectStatAbAttr extends PreStatChangeAbAttr {
-  private protectedStat: BattleStat | null;
+  private protectedStat?: BattleStat;
 
   constructor(protectedStat?: BattleStat) {
     super();
 
-    this.protectedStat = protectedStat ?? null;
+    this.protectedStat = protectedStat;
   }
 
   applyPreStatChange(pokemon: Pokemon, passive: boolean, stat: BattleStat, cancelled: Utils.BooleanHolder, args: any[]): boolean {
-    if (!this.protectedStat || stat === this.protectedStat) {
+    if (Utils.isNullOrUndefined(this.protectedStat) || stat === this.protectedStat) {
       cancelled.value = true;
       return true;
     }

src/test/abilities/hyper_cutter.test.ts

@@ -0,0 +1,58 @@
+import { BattleStat } from "#app/data/battle-stat";
+import { Abilities } from "#enums/abilities";
+import { Moves } from "#enums/moves";
+import { Species } from "#enums/species";
+import GameManager from "#test/utils/gameManager";
+import { getMovePosition } from "#test/utils/gameManagerUtils";
+import { SPLASH_ONLY } from "#test/utils/testUtils";
+import Phaser from "phaser";
+import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
+
+describe("Abilities - Hyper Cutter", () => {
+  let phaserGame: Phaser.Game;
+  let game: GameManager;
+
+  beforeAll(() => {
+    phaserGame = new Phaser.Game({
+      type: Phaser.HEADLESS,
+    });
+  });
+
+  afterEach(() => {
+    game.phaseInterceptor.restoreOg();
+  });
+
+  beforeEach(() => {
+    game = new GameManager(phaserGame);
+    game.override
+      .battleType("single")
+      .moveset([Moves.SAND_ATTACK, Moves.NOBLE_ROAR, Moves.DEFOG, Moves.OCTOLOCK])
+      .ability(Abilities.BALL_FETCH)
+      .enemySpecies(Species.SHUCKLE)
+      .enemyAbility(Abilities.HYPER_CUTTER)
+      .enemyMoveset(SPLASH_ONLY);
+  });
+
+  // Reference Link: https://bulbapedia.bulbagarden.net/wiki/Hyper_Cutter_(Ability)
+
+  it("only prevents ATK drops", async () => {
+    await game.startBattle();
+
+    const enemy = game.scene.getEnemyPokemon()!;
+
+    game.doAttack(getMovePosition(game.scene, 0, Moves.OCTOLOCK));
+    await game.toNextTurn();
+    game.doAttack(getMovePosition(game.scene, 0, Moves.DEFOG));
+    await game.toNextTurn();
+    game.doAttack(getMovePosition(game.scene, 0, Moves.NOBLE_ROAR));
+    await game.toNextTurn();
+    game.doAttack(getMovePosition(game.scene, 0, Moves.SAND_ATTACK));
+    await game.toNextTurn();
+    game.override.moveset([Moves.STRING_SHOT]);
+    game.doAttack(getMovePosition(game.scene, 0, Moves.STRING_SHOT));
+    await game.toNextTurn();
+
+    expect(enemy.summonData.battleStats[BattleStat.ATK]).toEqual(0);
+    [BattleStat.ACC, BattleStat.DEF, BattleStat.EVA, BattleStat.SPATK, BattleStat.SPDEF, BattleStat.SPD].forEach((stat: number) => expect(enemy.summonData.battleStats[stat]).toBeLessThan(0));
+  });
+});

src/utils.ts

@@ -552,3 +552,11 @@ export function capitalizeString(str: string, sep: string, lowerFirstChar: boole
   }
   return null;
 }
+
+/**
+ * Returns if an object is null or undefined
+ * @param object
+ */
+export function isNullOrUndefined(object: any): boolean {
+  return null === object || undefined === object;
+}