[Bug] Stakeout should trigger if the enemy switches with U-Turn/etc (#4918)

src/data/ability.ts

@@ -5953,7 +5953,7 @@ export function initAbilities() {
       .bypassFaint()
       .partial(), // Meteor form should protect against status effects and yawn
     new Ability(Abilities.STAKEOUT, 7)
-      .attr(MovePowerBoostAbAttr, (user, target, move) => user?.scene.currentBattle.turnCommands[target?.getBattlerIndex() ?? BattlerIndex.ATTACKER]?.command === Command.POKEMON, 2),
+      .attr(MovePowerBoostAbAttr, (user, target, move) => !!target?.turnData.switchedInThisTurn, 2),
     new Ability(Abilities.WATER_BUBBLE, 7)
       .attr(ReceivedTypeDamageMultiplierAbAttr, Type.FIRE, 0.5)
       .attr(MoveTypePowerBoostAbAttr, Type.WATER, 2)

src/test/abilities/stakeout.test.ts

@@ -0,0 +1,85 @@
+import { BattlerIndex } from "#app/battle";
+import { isBetween } from "#app/utils";
+import { Abilities } from "#enums/abilities";
+import { Moves } from "#enums/moves";
+import { Species } from "#enums/species";
+import GameManager from "#test/utils/gameManager";
+import Phaser from "phaser";
+import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
+
+describe("Abilities - Stakeout", () => {
+  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
+      .moveset([ Moves.SPLASH, Moves.SURF ])
+      .ability(Abilities.STAKEOUT)
+      .battleType("single")
+      .disableCrits()
+      .startingLevel(100)
+      .enemyLevel(100)
+      .enemySpecies(Species.SNORLAX)
+      .enemyAbility(Abilities.BALL_FETCH)
+      .enemyMoveset([ Moves.SPLASH, Moves.FLIP_TURN ])
+      .startingWave(5);
+  });
+
+  it("should do double damage to a pokemon that switched out", async () => {
+    await game.classicMode.startBattle([ Species.MILOTIC ]);
+
+    const [ enemy1, ] = game.scene.getEnemyParty();
+
+    game.move.select(Moves.SURF);
+    await game.forceEnemyMove(Moves.SPLASH);
+    await game.toNextTurn();
+    const damage1 = enemy1.getInverseHp();
+    enemy1.hp = enemy1.getMaxHp();
+
+    game.move.select(Moves.SPLASH);
+    game.forceEnemyToSwitch();
+    await game.toNextTurn();
+
+    game.move.select(Moves.SURF);
+    game.forceEnemyToSwitch();
+    await game.toNextTurn();
+
+    expect(enemy1.isFainted()).toBe(false);
+    expect(isBetween(enemy1.getInverseHp(), (damage1 * 2) - 5, (damage1 * 2) + 5)).toBe(true);
+  });
+
+  it("should do double damage to a pokemon that switched out via U-Turn/etc", async () => {
+    await game.classicMode.startBattle([ Species.MILOTIC ]);
+
+    const [ enemy1, ] = game.scene.getEnemyParty();
+
+    game.move.select(Moves.SURF);
+    await game.forceEnemyMove(Moves.SPLASH);
+    await game.toNextTurn();
+    const damage1 = enemy1.getInverseHp();
+    enemy1.hp = enemy1.getMaxHp();
+
+    game.move.select(Moves.SPLASH);
+    await game.forceEnemyMove(Moves.FLIP_TURN);
+    await game.toNextTurn();
+
+    game.move.select(Moves.SURF);
+    await game.forceEnemyMove(Moves.FLIP_TURN);
+    await game.setTurnOrder([ BattlerIndex.ENEMY, BattlerIndex.PLAYER ]);
+    await game.toNextTurn();
+
+    expect(enemy1.isFainted()).toBe(false);
+    expect(isBetween(enemy1.getInverseHp(), (damage1 * 2) - 5, (damage1 * 2) + 5)).toBe(true);
+  });
+});