[Bug]: Fix #5010: roar and whirlwind missing fail message when against a trainer (#5659)

* [BUG] Fixes #5010 Roar and Whirlwind don´t display a fail message
Roar and Whirlwind should now display a fail message when
used against a trainer with only one pokémon left

* Apply suggestions from code review made by SirzBenjie

src/data/moves/move.ts

@@ -6390,8 +6390,23 @@ export class ForceSwitchOutAttr extends MoveEffectAttr {
     return (user, target, move) => {
       const switchOutTarget = (this.selfSwitch ? user : target);
       const player = switchOutTarget instanceof PlayerPokemon;
+      const forceSwitchAttr = move.getAttrs(ForceSwitchOutAttr).find(attr => attr.switchType === SwitchType.FORCE_SWITCH);
 
       if (!this.selfSwitch) {
+        if (move.hitsSubstitute(user, target)) {
+          return false;
+        }
+
+        // Check if the move is Roar or Whirlwind and if there is a trainer with only Pokémon left.
+        if (forceSwitchAttr && globalScene.currentBattle.trainer) {
+        const enemyParty = globalScene.getEnemyParty();
+        // Filter out any Pokémon that are not allowed in battle (e.g. fainted ones)
+        const remainingPokemon = enemyParty.filter(p => p.hp > 0 && p.isAllowedInBattle());
+          if (remainingPokemon.length <= 1) {
+            return false;
+          }
+        }
+
         // Dondozo with an allied Tatsugiri in its mouth cannot be forced out
         const commandedTag = switchOutTarget.getTag(BattlerTagType.COMMANDED);
         if (commandedTag?.getSourcePokemon()?.isActive(true)) {

test/moves/whirlwind.test.ts

@@ -10,6 +10,7 @@ import Phaser from "phaser";
 import { afterEach, beforeAll, beforeEach, describe, expect, it, vi } from "vitest";
 import { Status } from "#app/data/status-effect";
 import { StatusEffect } from "#enums/status-effect";
+import { globalScene } from "#app/global-scene";
 import { BattlerIndex } from "#app/battle";
 import { BattleType } from "#enums/battle-type";
 import { TrainerType } from "#enums/trainer-type";
@@ -161,6 +162,37 @@ describe("Moves - Whirlwind", () => {
     expect(eevee.isOnField()).toBe(false);
   });
 
+  it("should fail when player uses Whirlwind against an opponent with only one available Pokémon", async () => {
+    // Set up the battle scenario with the player knowing Whirlwind
+    game.override.startingWave(5).enemySpecies(Species.PIDGEY).moveset([Moves.WHIRLWIND]);
+    await game.classicMode.startBattle();
+
+    const enemyParty = game.scene.getEnemyParty();
+
+    // Ensure the opponent has only one available Pokémon
+    if (enemyParty.length > 1) {
+      enemyParty.slice(1).forEach(p => {
+        p.hp = 0;
+        p.status = new Status(StatusEffect.FAINT);
+      });
+    }
+    const eligibleEnemy = enemyParty.filter(p => p.hp > 0 && p.isAllowedInBattle());
+    expect(eligibleEnemy.length).toBe(1);
+
+    // Spy on the queueMessage function
+    const queueSpy = vi.spyOn(globalScene, "queueMessage");
+
+    // Player uses Whirlwind; opponent uses Splash
+    game.move.select(Moves.WHIRLWIND);
+    await game.forceEnemyMove(Moves.SPLASH);
+    await game.toNextTurn();
+
+    // Verify that the failure message is displayed for Whirlwind
+    expect(queueSpy).toHaveBeenCalledWith(expect.stringContaining("But it failed"));
+    // Verify the opponent's Splash message
+    expect(queueSpy).toHaveBeenCalledWith(expect.stringContaining("But nothing happened!"));
+  });
+
   it("should not pull in the other trainer's pokemon in a partner trainer battle", async () => {
     game.override
       .startingWave(2)