[Bug] Dancer no longer breaks "last hit only" moves, respects flinch + steadfast (#5945)

* WIP

* Fixed Dancer last hit, flinch move interaction

* Fixed steadfast interaction

* Fixed comment + flaky test

---------

Co-authored-by: NightKev <34855794+DayKev@users.noreply.github.com>

src/data/abilities/ability.ts

@@ -4438,6 +4438,7 @@ export class PostDancingMoveAbAttr extends PostMoveUsedAbAttr {
     simulated: boolean,
     args: any[]): void {
     if (!simulated) {
+      dancer.turnData.extraTurns++;
       // If the move is an AttackMove or a StatusMove the Dancer must replicate the move on the source of the Dance
       if (move.getMove() instanceof AttackMove || move.getMove() instanceof StatusMove) {
         const target = this.getTarget(dancer, source, targets);

src/data/battler-tags.ts

@@ -649,20 +649,14 @@ class NoRetreatTag extends TrappedTag {
  */
 export class FlinchedTag extends BattlerTag {
   constructor(sourceMove: MoveId) {
-    super(BattlerTagType.FLINCHED, [BattlerTagLapseType.PRE_MOVE, BattlerTagLapseType.TURN_END], 0, sourceMove);
+    super(BattlerTagType.FLINCHED, [BattlerTagLapseType.PRE_MOVE, BattlerTagLapseType.TURN_END], 1, sourceMove);
-  }
-
-  onAdd(pokemon: Pokemon): void {
-    super.onAdd(pokemon);
-
-    applyAbAttrs(FlinchEffectAbAttr, pokemon, null);
   }
 
   /**
-   * Cancels the Pokemon's next Move on the turn this tag is applied
+   * Cancels the flinched Pokemon's currently used move this turn if called mid-execution, or removes the tag at end of turn.
-   * @param pokemon The {@linkcode Pokemon} with this tag
+   * @param pokemon - The {@linkcode Pokemon} with this tag.
-   * @param lapseType The {@linkcode BattlerTagLapseType lapse type} used for this function call
+   * @param lapseType - The {@linkcode BattlerTagLapseType | lapse type} used for this function call.
-   * @returns `false` (This tag is always removed after applying its effects)
+   * @returns Whether the tag should remain active.
    */
   lapse(pokemon: Pokemon, lapseType: BattlerTagLapseType): boolean {
     if (lapseType === BattlerTagLapseType.PRE_MOVE) {
@@ -672,6 +666,8 @@ export class FlinchedTag extends BattlerTag {
           pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
         }),
       );
+      applyAbAttrs(FlinchEffectAbAttr, pokemon, null);
+      return true;
     }
 
     return super.lapse(pokemon, lapseType);

test/abilities/dancer.test.ts

@@ -1,8 +1,10 @@
 import { BattlerIndex } from "#app/battle";
+import { MoveResult } from "#app/field/pokemon";
 import type { MovePhase } from "#app/phases/move-phase";
 import { AbilityId } from "#enums/ability-id";
 import { MoveId } from "#enums/move-id";
 import { SpeciesId } from "#enums/species-id";
+import { Stat } from "#enums/stat";
 import GameManager from "#test/testUtils/gameManager";
 import Phaser from "phaser";
 import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
@@ -99,4 +101,43 @@ describe("Abilities - Dancer", () => {
     expect(currentPhase.pokemon).toBe(oricorio);
     expect(currentPhase.move.moveId).toBe(MoveId.REVELATION_DANCE);
   });
+
+  it("should not break subsequent last hit only moves", async () => {
+    game.override.battleStyle("single");
+    await game.classicMode.startBattle([SpeciesId.ORICORIO, SpeciesId.FEEBAS]);
+
+    const [oricorio, feebas] = game.scene.getPlayerParty();
+
+    game.move.use(MoveId.BATON_PASS);
+    game.doSelectPartyPokemon(1);
+    await game.move.forceEnemyMove(MoveId.SWORDS_DANCE);
+    await game.setTurnOrder([BattlerIndex.ENEMY, BattlerIndex.PLAYER]);
+    await game.phaseInterceptor.to("TurnEndPhase");
+
+    expect(game.phaseInterceptor.log).toContain("SwitchSummonPhase");
+    expect(game.field.getPlayerPokemon()).toBe(feebas);
+    expect(feebas.getStatStage(Stat.ATK)).toBe(2);
+    expect(oricorio.isOnField()).toBe(false);
+    expect(oricorio.visible).toBe(false);
+  });
+
+  it("should not trigger while flinched", async () => {
+    game.override.battleStyle("double").moveset(MoveId.SPLASH).enemyMoveset([MoveId.SWORDS_DANCE, MoveId.FAKE_OUT]);
+    await game.classicMode.startBattle([SpeciesId.ORICORIO]);
+
+    const oricorio = game.scene.getPlayerPokemon()!;
+    expect(oricorio).toBeDefined();
+
+    // get faked out and copy swords dance
+    game.move.select(MoveId.SPLASH);
+    await game.move.forceEnemyMove(MoveId.SWORDS_DANCE);
+    await game.move.forceEnemyMove(MoveId.FAKE_OUT, BattlerIndex.PLAYER);
+    await game.phaseInterceptor.to("TurnEndPhase");
+
+    expect(oricorio.getLastXMoves(-1)[0]).toMatchObject({
+      move: MoveId.NONE,
+      result: MoveResult.FAIL,
+    });
+    expect(oricorio.getStatStage(Stat.ATK)).toBe(0);
+  });
 });

test/moves/instruct.test.ts

@@ -1,13 +1,15 @@
 import { BattlerIndex } from "#app/battle";
+import { allMoves } from "#app/data/data-lists";
 import type Pokemon from "#app/field/pokemon";
 import { MoveResult } from "#app/field/pokemon";
 import type { MovePhase } from "#app/phases/move-phase";
 import { AbilityId } from "#enums/ability-id";
 import { MoveId } from "#enums/move-id";
 import { SpeciesId } from "#enums/species-id";
+import { Stat } from "#enums/stat";
 import GameManager from "#test/testUtils/gameManager";
 import Phaser from "phaser";
-import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
+import { afterEach, beforeAll, beforeEach, describe, expect, it, vi } from "vitest";
 
 describe("Moves - Instruct", () => {
   let phaserGame: Phaser.Game;
@@ -34,7 +36,8 @@ describe("Moves - Instruct", () => {
     game.override
       .battleStyle("single")
       .enemySpecies(SpeciesId.SHUCKLE)
-      .enemyAbility(AbilityId.NO_GUARD)
+      .enemyAbility(AbilityId.BALL_FETCH)
+      .passiveAbility(AbilityId.NO_GUARD)
       .enemyLevel(100)
       .startingLevel(100)
       .disableCrits();
@@ -536,4 +539,27 @@ describe("Moves - Instruct", () => {
 
     expect(ivysaur.turnData.attacksReceived.length).toBe(15);
   });
+
+  it("should respect prior flinches and trigger Steadfast", async () => {
+    game.override.battleStyle("double");
+    vi.spyOn(allMoves[MoveId.AIR_SLASH], "chance", "get").mockReturnValue(100);
+    await game.classicMode.startBattle([SpeciesId.AUDINO, SpeciesId.ABRA]);
+
+    // Fake enemy 1 having attacked prior
+    const [, player2, enemy1, enemy2] = game.scene.getField();
+    enemy1.pushMoveHistory({ move: MoveId.ABSORB, targets: [BattlerIndex.PLAYER] });
+    game.field.mockAbility(enemy1, AbilityId.STEADFAST);
+
+    game.move.use(MoveId.AIR_SLASH, BattlerIndex.PLAYER, BattlerIndex.ENEMY);
+    game.move.use(MoveId.INSTRUCT, BattlerIndex.PLAYER_2, BattlerIndex.ENEMY);
+    await game.move.forceEnemyMove(MoveId.ABSORB);
+    await game.move.forceEnemyMove(MoveId.INSTRUCT, BattlerIndex.ENEMY);
+    await game.setTurnOrder([BattlerIndex.PLAYER, BattlerIndex.ENEMY, BattlerIndex.PLAYER_2, BattlerIndex.ENEMY_2]);
+    await game.toEndOfTurn();
+
+    expect(enemy1.getLastXMoves(-1).map(m => m.move)).toEqual([MoveId.NONE, MoveId.NONE, MoveId.NONE, MoveId.ABSORB]);
+    expect(enemy1.getStatStage(Stat.SPD)).toBe(3);
+    expect(player2.getLastXMoves()[0].result).toBe(MoveResult.SUCCESS);
+    expect(enemy2.getLastXMoves()[0].result).toBe(MoveResult.SUCCESS);
+  });
 });