[Bug] Fix weather form changes not changing with weather abilities

https://github.com/pagefaultgames/pokerogue/pull/5857

* Add test for forecast

* Fix PostSummonFormChangeByWeatherAbAttr

* Fix overrides in forecast test

* Remove a test whose trigger conditions can no longer happen

* Update src/data/abilities/ability.ts

Co-authored-by: Dean <69436131+emdeann@users.noreply.github.com>

* Fix missing tsdoc param

* Apply kev's suggestions from code review

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

* Simplify PostSummonFormChangeByWeather's canApplyPostSummon

* Fix unused params that messed up after rebase

* Fix form change import

Messed up due to improper rebase

---------

Co-authored-by: Dean <69436131+emdeann@users.noreply.github.com>
Co-authored-by: NightKev <34855794+DayKev@users.noreply.github.com>

src/data/abilities/ability.ts

@@ -24,11 +24,11 @@ import { allMoves } from "../data-lists";
 import { ArenaTagSide } from "#enums/arena-tag-side";
 import { BerryModifier, HitHealModifier, PokemonHeldItemModifier } from "#app/modifier/modifier";
 import { TerrainType } from "#app/data/terrain";
+import { pokemonFormChanges } from "../pokemon-forms";
 import {
-  SpeciesFormChangeRevertWeatherFormTrigger,
   SpeciesFormChangeWeatherTrigger,
+  SpeciesFormChangeAbilityTrigger,
 } from "../pokemon-forms/form-change-triggers";
-import { SpeciesFormChangeAbilityTrigger } from "../pokemon-forms/form-change-triggers";
 import i18next from "i18next";
 import { Command } from "#enums/command";
 import { BerryModifierType } from "#app/modifier/modifier-type";
@@ -3971,27 +3971,32 @@ export class PostSummonFormChangeByWeatherAbAttr extends PostSummonAbAttr {
     this.ability = ability;
   }
 
+  /**
+   * Determine if the pokemon has a forme change that is triggered by the weather
+   *
+   * @param pokemon - The pokemon with the forme change ability
+   * @param _passive - unused
+   * @param _simulated - unused
+   * @param _args - unused
+   */
   override canApplyPostSummon(pokemon: Pokemon, _passive: boolean, _simulated: boolean, _args: any[]): boolean {
-    const isCastformWithForecast =
+    return !!pokemonFormChanges[pokemon.species.speciesId]?.some(
-      pokemon.species.speciesId === SpeciesId.CASTFORM && this.ability === AbilityId.FORECAST;
+      fc => fc.findTrigger(SpeciesFormChangeWeatherTrigger) && fc.canChange(pokemon),
-    const isCherrimWithFlowerGift =
+    );
-      pokemon.species.speciesId === SpeciesId.CHERRIM && this.ability === AbilityId.FLOWER_GIFT;
-    return isCastformWithForecast || isCherrimWithFlowerGift;
   }
 
   /**
-   * Calls the {@linkcode BattleScene.triggerPokemonFormChange | triggerPokemonFormChange} for both
+   * Trigger the pokemon's forme change by invoking
-   * {@linkcode SpeciesFormChange.SpeciesFormChangeWeatherTrigger | SpeciesFormChangeWeatherTrigger} and
+   * {@linkcode BattleScene.triggerPokemonFormChange | triggerPokemonFormChange}
-   * {@linkcode SpeciesFormChange.SpeciesFormChangeWeatherTrigger | SpeciesFormChangeRevertWeatherFormTrigger} if it
+   *
-   * is the specific Pokemon and ability
+   * @param pokemon - The Pokemon with this ability
-   * @param {Pokemon} pokemon the Pokemon with this ability
+   * @param _passive - unused
-   * @param _passive n/a
+   * @param simulated - unused
-   * @param _args n/a
+   * @param _args - unused
    */
   override applyPostSummon(pokemon: Pokemon, _passive: boolean, simulated: boolean, _args: any[]): void {
     if (!simulated) {
       globalScene.triggerPokemonFormChange(pokemon, SpeciesFormChangeWeatherTrigger);
-      globalScene.triggerPokemonFormChange(pokemon, SpeciesFormChangeRevertWeatherFormTrigger);
     }
   }
 }
@@ -5301,10 +5306,11 @@ export class PostWeatherChangeFormChangeAbAttr extends PostWeatherChangeAbAttr {
   /**
    * Calls {@linkcode Arena.triggerWeatherBasedFormChangesToNormal | triggerWeatherBasedFormChangesToNormal} when the
    * weather changed to form-reverting weather, otherwise calls {@linkcode Arena.triggerWeatherBasedFormChanges | triggerWeatherBasedFormChanges}
-   * @param {Pokemon} _pokemon the Pokemon with this ability
+   * @param _pokemon - The Pokemon with this ability
-   * @param _passive n/a
+   * @param _passive - unused
-   * @param _weather n/a
+   * @param simulated - unused
-   * @param _args n/a
+   * @param _weather - unused
+   * @param _args - unused
    */
   override applyPostWeatherChange(
     _pokemon: Pokemon,

test/abilities/forecast.test.ts

@@ -21,26 +21,10 @@ describe("Abilities - Forecast", () => {
   const RAINY_FORM = 2;
   const SNOWY_FORM = 3;
 
-  /**
-   * Tests form changes based on weather changes
-   * @param {GameManager} game The game manager instance
-   * @param {WeatherType} weather The active weather to set
-   * @param form The expected form based on the active weather
-   * @param initialForm The initial form pre form change
-   */
-  const testWeatherFormChange = async (game: GameManager, weather: WeatherType, form: number, initialForm?: number) => {
-    game.override.weather(weather).starterForms({ [SpeciesId.CASTFORM]: initialForm });
-    await game.classicMode.startBattle([SpeciesId.CASTFORM]);
-
-    game.move.select(MoveId.SPLASH);
-
-    expect(game.scene.getPlayerPokemon()?.formIndex).toBe(form);
-  };
-
   /**
    * Tests reverting to normal form when Cloud Nine/Air Lock is active on the field
-   * @param {GameManager} game The game manager instance
+   * @param game - The game manager instance
-   * @param {AbilityId} ability The ability that is active on the field
+   * @param ability - The ability that is active on the field
    */
   const testRevertFormAgainstAbility = async (game: GameManager, ability: AbilityId) => {
     game.override.starterForms({ [SpeciesId.CASTFORM]: SUNNY_FORM }).enemyAbility(ability);
@@ -191,10 +175,6 @@ describe("Abilities - Forecast", () => {
     30 * 1000,
   );
 
-  it("reverts to Normal Form during Clear weather", async () => {
-    await testWeatherFormChange(game, WeatherType.NONE, NORMAL_FORM, SUNNY_FORM);
-  });
-
   it("reverts to Normal Form if a Pokémon on the field has Air Lock", async () => {
     await testRevertFormAgainstAbility(game, AbilityId.AIR_LOCK);
   });
@@ -277,4 +257,20 @@ describe("Abilities - Forecast", () => {
 
     expect(castform.formIndex).toBe(NORMAL_FORM);
   });
+
+  // NOTE: The following pairs of tests are intentionally testing the same scenario, switching the player and enemy pokemon
+  // as this is a regression test where the order of player and enemy mattered.
+  it("should trigger player's form change when summoned at the same time as an enemy with a weather changing ability", async () => {
+    game.override.enemyAbility(AbilityId.DROUGHT);
+    await game.classicMode.startBattle([SpeciesId.CASTFORM, SpeciesId.MAGIKARP]);
+    const castform = game.scene.getPlayerPokemon()!;
+    expect(castform.formIndex).toBe(SUNNY_FORM);
+  });
+
+  it("should trigger enemy's form change when summoned at the same time as a player with a weather changing ability", async () => {
+    game.override.ability(AbilityId.DROUGHT).enemySpecies(SpeciesId.CASTFORM).enemyAbility(AbilityId.FORECAST);
+    await game.classicMode.startBattle([SpeciesId.MAGIKARP]);
+    const castform = game.scene.getEnemyPokemon()!;
+    expect(castform.formIndex).toBe(SUNNY_FORM);
+  });
 });