Fix #2735: Hazard moves incorrectly require targets (#5635)

* Fix #2735: Hazard moves incorrectly require targets
Hazard moves should no longer require targets to successfully execute

* Apply suggestions from code review made by NightKev

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

---------

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

src/data/battle-anims.ts

@@ -1428,7 +1428,8 @@ export class MoveAnim extends BattleAnim {
   public move: Moves;
 
   constructor(move: Moves, user: Pokemon, target: BattlerIndex, playOnEmptyField = false) {
-    super(user, globalScene.getField()[target], playOnEmptyField);
+    // Set target to the user pokemon if no target is found to avoid crashes
+    super(user, globalScene.getField()[target] ?? user, playOnEmptyField);
 
     this.move = move;
   }

src/data/moves/move.ts

@@ -5928,7 +5928,7 @@ export class AddArenaTagAttr extends MoveEffectAttr {
     }
 
     if ((move.chance < 0 || move.chance === 100 || user.randSeedInt(100) < move.chance) && user.getLastXMoves(1)[0]?.result === MoveResult.SUCCESS) {
-      const side = (this.selfSideTarget ? user : target).isPlayer() ? ArenaTagSide.PLAYER : ArenaTagSide.ENEMY;
+      const side = ((this.selfSideTarget ? user : target).isPlayer() !== (move.hasAttr(AddArenaTrapTagAttr) && target === user)) ? ArenaTagSide.PLAYER : ArenaTagSide.ENEMY;
       globalScene.arena.addTag(this.tagType, this.turnCount, move.id, user.id, side);
       return true;
     }
@@ -5977,7 +5977,7 @@ export class RemoveArenaTagsAttr extends MoveEffectAttr {
 export class AddArenaTrapTagAttr extends AddArenaTagAttr {
   getCondition(): MoveConditionFunc {
     return (user, target, move) => {
-      const side = (this.selfSideTarget ? user : target).isPlayer() ? ArenaTagSide.PLAYER : ArenaTagSide.ENEMY;
+      const side = (this.selfSideTarget !== user.isPlayer()) ? ArenaTagSide.ENEMY : ArenaTagSide.PLAYER;
       const tag = globalScene.arena.getTagOnSide(this.tagType, side) as ArenaTrapTag;
       if (!tag) {
         return true;

src/phases/move-effect-phase.ts

@@ -26,6 +26,7 @@ import {
 } from "#app/data/battler-tags";
 import type { MoveAttr } from "#app/data/moves/move";
 import {
+  AddArenaTrapTagAttr,
   applyFilteredMoveAttrs,
   applyMoveAttrs,
   AttackMove,
@@ -209,12 +210,12 @@ export class MoveEffectPhase extends PokemonPhase {
       targets.some(t => t.hasAbilityWithAttr(ReflectStatusMoveAbAttr) || !!t.getTag(BattlerTagType.MAGIC_COAT));
 
     /**
-     * If no targets are left for the move to hit (FAIL), or the invoked move is non-reflectable, single-target
+     * If no targets are left for the move to hit and it is not a hazard move (FAIL), or the invoked move is non-reflectable, single-target
      * (and not random target) and failed the hit check against its target (MISS), log the move
      * as FAILed or MISSed (depending on the conditions above) and end this phase.
      */
     if (
-      !hasActiveTargets ||
+      (!hasActiveTargets && !move.hasAttr(AddArenaTrapTagAttr)) ||
       (!mayBounce &&
         !move.hasAttr(VariableTargetAttr) &&
         !move.isMultiTarget() &&
@@ -239,18 +240,28 @@ export class MoveEffectPhase extends PokemonPhase {
       return this.end();
     }
 
-    const playOnEmptyField = globalScene.currentBattle?.mysteryEncounter?.hasBattleAnimationsWithoutTargets ?? false;
-    // Move animation only needs one target
-    new MoveAnim(move.id as Moves, user, this.getFirstTarget()!.getBattlerIndex(), playOnEmptyField).play(
-      move.hitsSubstitute(user, this.getFirstTarget()!),
-      () => {
+    const playOnEmptyField =
+      (globalScene.currentBattle?.mysteryEncounter?.hasBattleAnimationsWithoutTargets ?? false) ||
+      (!hasActiveTargets && move.hasAttr(AddArenaTrapTagAttr));
+    // Move animation only needs one target. The attacker is used as a fallback.
+    new MoveAnim(
+      move.id as Moves,
+      user,
+      this.getFirstTarget()?.getBattlerIndex() ?? BattlerIndex.ATTACKER,
+      playOnEmptyField,
+    ).play(move.hitsSubstitute(user, this.getFirstTarget()!), () => {
       /** Has the move successfully hit a target (for damage) yet? */
       let hasHit = false;
 
       // Prevent ENEMY_SIDE targeted moves from occurring twice in double battles
       // and check which target will magic bounce.
+      // In the event that the move is a hazard move, there may be no target and the move should still succeed.
+      // In this case, the user is used as the "target" to prevent a crash.
+      // This should not affect normal execution of the move otherwise.
       const trueTargets: Pokemon[] =
-          move.moveTarget !== MoveTarget.ENEMY_SIDE
+        !hasActiveTargets && move.hasAttr(AddArenaTrapTagAttr)
+          ? [user]
+          : move.moveTarget !== MoveTarget.ENEMY_SIDE
             ? targets
             : (() => {
                 const magicCoatTargets = targets.filter(
@@ -338,9 +349,7 @@ export class MoveEffectPhase extends PokemonPhase {
               queuedPhases.push(new HideAbilityPhase());
             }
 
-            queuedPhases.push(
-              new MovePhase(target, newTargets, new PokemonMove(move.id, 0, 0, true), true, true, true),
-            );
+          queuedPhases.push(new MovePhase(target, newTargets, new PokemonMove(move.id, 0, 0, true), true, true, true));
           continue;
         }
 
@@ -357,7 +366,10 @@ export class MoveEffectPhase extends PokemonPhase {
         if (
           target.switchOutStatus ||
           isCommanding ||
-            (!isImmune && !isProtected && !targetHitChecks[target.getBattlerIndex()])
+          (!isImmune &&
+            !isProtected &&
+            !targetHitChecks[target.getBattlerIndex()] &&
+            !move.hasAttr(AddArenaTrapTagAttr))
         ) {
           this.stopMultiHit(target);
           if (!target.switchOutStatus) {
@@ -501,8 +513,7 @@ export class MoveEffectPhase extends PokemonPhase {
       }
 
       this.end();
-      },
-    );
+    });
   }
 
   public override end(): void {

src/phases/move-phase.ts

@@ -15,6 +15,7 @@ import type { DelayedAttackTag } from "#app/data/arena-tag";
 import { CommonAnim } from "#app/data/battle-anims";
 import { BattlerTagLapseType, CenterOfAttentionTag } from "#app/data/battler-tags";
 import {
+  AddArenaTrapTagAttr,
   allMoves,
   applyMoveAttrs,
   BypassRedirectAttr,
@@ -201,7 +202,10 @@ export class MovePhase extends BattlePhase {
     const targets = this.getActiveTargetPokemon();
     const moveQueue = this.pokemon.getMoveQueue();
 
-    if (targets.length === 0 || (moveQueue.length && moveQueue[0].move === Moves.NONE)) {
+    if (
+      (targets.length === 0 && !this.move.getMove().hasAttr(AddArenaTrapTagAttr)) ||
+      (moveQueue.length && moveQueue[0].move === Moves.NONE)
+    ) {
       this.showMoveText();
       this.showFailedText();
       this.cancel();

test/moves/spikes.test.ts

@@ -4,6 +4,7 @@ import { Species } from "#enums/species";
 import GameManager from "#test/testUtils/gameManager";
 import Phaser from "phaser";
 import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
+import { ArenaTagSide, ArenaTrapTag } from "#app/data/arena-tag";
 
 describe("Moves - Spikes", () => {
   let phaserGame: Phaser.Game;
@@ -77,4 +78,17 @@ describe("Moves - Spikes", () => {
     const enemy = game.scene.getEnemyParty()[0];
     expect(enemy.hp).toBeLessThan(enemy.getMaxHp());
   }, 20000);
+
+  it("should work when all targets fainted", async () => {
+    game.override.enemySpecies(Species.DIGLETT);
+    game.override.battleType("double");
+    game.override.startingLevel(50);
+    await game.classicMode.startBattle([Species.RAYQUAZA, Species.ROWLET]);
+
+    game.move.select(Moves.EARTHQUAKE);
+    game.move.select(Moves.SPIKES, 1);
+    await game.phaseInterceptor.to("TurnEndPhase");
+
+    expect(game.scene.arena.getTagOnSide(ArenaTrapTag, ArenaTagSide.ENEMY)).toBeDefined();
+  }, 20000);
 });