[Bug][Refactor] Fix loading arena tags (#6110)

* Improve type safety; add missing loadTag overrides to wish and neutralizing gas

* More automatic type safety for arena tags

* Fixup wording of lead comment in arena-tag.ts

* Apply kev's suggestions from code review

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

* Allow abstract constructors for arena methods

* Address dean's comments from code review

* Add missing newline after interface definition

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

* Apply suggestions from code review

Co-authored-by: Bertie690 <136088738+Bertie690@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Bertie690 <136088738+Bertie690@users.noreply.github.com>

* Format with biome

* Update tsdoc of ConditionalProtectTag

Co-authored-by: Bertie690 <136088738+Bertie690@users.noreply.github.com>

* Apply kev's suggestions from code review

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

---------

Co-authored-by: NightKev <34855794+DayKev@users.noreply.github.com>
Co-authored-by: Bertie690 <136088738+Bertie690@users.noreply.github.com>

src/@types/arena-tags.ts

@@ -0,0 +1,48 @@
+import type { ArenaTagTypeMap } from "#data/arena-tag";
+import type { ArenaTagType } from "#enums/arena-tag-type";
+import type { NonFunctionProperties } from "./type-helpers";
+
+/** Subset of {@linkcode ArenaTagType}s that apply some negative effect to pokemon that switch in ({@link https://bulbapedia.bulbagarden.net/wiki/List_of_moves_that_cause_entry_hazards#List_of_traps | entry hazards} and Imprison. */
+export type ArenaTrapTagType =
+  | ArenaTagType.STICKY_WEB
+  | ArenaTagType.SPIKES
+  | ArenaTagType.TOXIC_SPIKES
+  | ArenaTagType.STEALTH_ROCK
+  | ArenaTagType.IMPRISON;
+
+/** Subset of {@linkcode ArenaTagType}s that are considered delayed attacks */
+export type ArenaDelayedAttackTagType = ArenaTagType.FUTURE_SIGHT | ArenaTagType.DOOM_DESIRE;
+
+/** Subset of {@linkcode ArenaTagType}s that create {@link https://bulbapedia.bulbagarden.net/wiki/Category:Screen-creating_moves | screens}. */
+export type ArenaScreenTagType = ArenaTagType.REFLECT | ArenaTagType.LIGHT_SCREEN | ArenaTagType.AURORA_VEIL;
+
+/** Subset of {@linkcode ArenaTagType}s for moves that add protection */
+export type TurnProtectArenaTagType =
+  | ArenaTagType.QUICK_GUARD
+  | ArenaTagType.WIDE_GUARD
+  | ArenaTagType.MAT_BLOCK
+  | ArenaTagType.CRAFTY_SHIELD;
+
+/** Subset of {@linkcode ArenaTagType}s that cannot persist across turns, and thus should not be serialized in {@linkcode SessionSaveData}. */
+export type NonSerializableArenaTagType = ArenaTagType.NONE | TurnProtectArenaTagType | ArenaTagType.ION_DELUGE;
+
+/** Subset of {@linkcode ArenaTagType}s that may persist across turns, and thus must be serialized in {@linkcode SessionSaveData}. */
+export type SerializableArenaTagType = Exclude<ArenaTagType, NonSerializableArenaTagType>;
+
+/**
+ * Type-safe representation of the serializable data of an ArenaTag
+ */
+export type ArenaTagTypeData = NonFunctionProperties<
+  ArenaTagTypeMap[keyof {
+    [K in keyof ArenaTagTypeMap as K extends SerializableArenaTagType ? K : never]: ArenaTagTypeMap[K];
+  }]
+>;
+
+/** Dummy, typescript-only declaration to ensure that
+ * {@linkcode ArenaTagTypeMap} has a map for all ArenaTagTypes.
+ *
+ * If an arena tag is missing from the map, typescript will throw an error on this statement.
+ *
+ * ⚠️ Does not actually exist at runtime, so it must not be used!
+ */
+declare const EnsureAllArenaTagTypesAreMapped: ArenaTagTypeMap[ArenaTagType] & never;

src/@types/type-helpers.ts

@@ -44,3 +44,34 @@ export type Mutable<T> = {
 export type InferKeys<O extends Record<keyof any, unknown>, V extends EnumValues<O>> = {
   [K in keyof O]: O[K] extends V ? K : never;
 }[keyof O];
+
+/**
+ * Type helper that matches any `Function` type. Equivalent to `Function`, but will not raise a warning from Biome.
+ */
+export type AnyFn = (...args: any[]) => any;
+
+/**
+ * Type helper to extract non-function properties from a type.
+ *
+ * @remarks
+ * Useful to produce a type that is roughly the same as the type of `{... obj}`, where `obj` is an instance of `T`.
+ * A couple of differences:
+ * - Private and protected properties are not included.
+ * - Nested properties are not recursively extracted. For this, use {@linkcode NonFunctionPropertiesRecursive}
+ */
+export type NonFunctionProperties<T> = {
+  [K in keyof T as T[K] extends AnyFn ? never : K]: T[K];
+};
+
+/**
+ * Type helper to extract out non-function properties from a type, recursively applying to nested properties.
+ */
+export type NonFunctionPropertiesRecursive<Class> = {
+  [K in keyof Class as Class[K] extends AnyFn ? never : K]: Class[K] extends Array<infer U>
+    ? NonFunctionPropertiesRecursive<U>[]
+    : Class[K] extends object
+      ? NonFunctionPropertiesRecursive<Class[K]>
+      : Class[K];
+};
+
+export type AbstractConstructor<T> = abstract new (...args: any[]) => T;

src/data/arena-tag.ts

@@ -19,19 +19,88 @@ import { Stat } from "#enums/stat";
 import { StatusEffect } from "#enums/status-effect";
 import type { Arena } from "#field/arena";
 import type { Pokemon } from "#field/pokemon";
+import type {
+  ArenaDelayedAttackTagType,
+  ArenaScreenTagType,
+  ArenaTagTypeData,
+  ArenaTrapTagType,
+  SerializableArenaTagType,
+} from "#types/arena-tags";
+import type { Mutable, NonFunctionProperties } from "#types/type-helpers";
 import { BooleanHolder, NumberHolder, toDmgValue } from "#utils/common";
 import i18next from "i18next";
 
-// TODO: Add a class for tags that explicitly REQUIRE a source move (as currently we have a lot of bangs)
+/*
+ArenaTags are are meant for effects that are tied to the arena (as opposed to a specific pokemon).
+Examples include (but are not limited to)
+- Cross-turn effects that persist even if the user/target switches out, such as Wish, Future Sight, and Happy Hour
+- Effects that are applied to a specific side of the field, such as Crafty Shield, Reflect, and Spikes
+- Field-Effects, like Gravity and Trick Room
 
-export abstract class ArenaTag {
+Any arena tag that persists across turns *must* extend from `SerializableArenaTag` in the class definition signature.
-  constructor(
+
-    public tagType: ArenaTagType,
+Serializable ArenaTags have strict rules for their fields.
-    public turnCount: number,
+These rules ensure that only the data necessary to reconstruct the tag is serialized, and that the
-    public sourceMove?: MoveId,
+session loader is able to deserialize saved tags correctly.
-    public sourceId?: number,
+
-    public side: ArenaTagSide = ArenaTagSide.BOTH,
+If the data is static (i.e. it is always the same for all instances of the class, such as the 
-  ) {}
+type that is weakened by Mud Sport/Water Sport), then it must not be defined as a field, and must
+instead be defined as a getter.
+A static property is also acceptable, though static properties are less ergonomic with inheritance.
+
+If the data is mutable (i.e. it can change over the course of the tag's lifetime), then it *must*
+be defined as a field, and it must be set in the `loadTag` method.
+Such fields cannot be marked as `private/protected`, as if they were, typescript would omit them from
+types that are based off of the class, namely, `ArenaTagTypeData`. It is preferrable to trade the
+type-safety of private/protected fields for the type safety when deserializing arena tags from save data.
+
+For data that is mutable only within a turn (e.g. SuppressAbilitiesTag's beingRemoved field),
+where it does not make sense to be serialized, the field should use ES2020's private field syntax (a `#` prepended to the field name).
+If the field should be accessible outside of the class, then a public getter should be used.
+*/
+
+/** Interface containing the serializable fields of ArenaTagData. */
+interface BaseArenaTag {
+  /**
+   * The tag's remaining duration. Setting to any number `<=0` will make the tag's duration effectively infinite.
+   */
+  turnCount: number;
+  /**
+   * The {@linkcode MoveId} that created this tag, or `undefined` if not set by a move.
+   */
+  sourceMove?: MoveId;
+  /**
+   * The {@linkcode Pokemon.id | PID} of the {@linkcode Pokemon} having created the tag, or `undefined` if not set by a Pokemon.
+   * @todo Implement handling for `ArenaTag`s created by non-pokemon sources (most tags will throw errors without a source)
+   */
+  // Note: Intentionally not using `?`, as the property should always exist, but just be undefined if not present.
+  sourceId: number | undefined;
+  /**
+   * The {@linkcode ArenaTagSide | side of the field} that this arena tag affects.
+   * @defaultValue `ArenaTagSide.BOTH`
+   */
+  side: ArenaTagSide;
+}
+
+/**
+ * An {@linkcode ArenaTag} represents a semi-persistent effect affecting a given _side_ of the field.
+ * Unlike {@linkcode BattlerTag}s (which are tied to individual {@linkcode Pokemon}), `ArenaTag`s function independently of
+ * the Pokemon currently on-field, only cleared on arena reset or through their respective {@linkcode ArenaTag.lapse | lapse} methods.
+ */
+export abstract class ArenaTag implements BaseArenaTag {
+  /** The type of the arena tag */
+  public abstract readonly tagType: ArenaTagType;
+  public turnCount: number;
+  public sourceMove?: MoveId;
+  public sourceId: number | undefined;
+  public side: ArenaTagSide;
+
+  constructor(turnCount: number, sourceMove?: MoveId, sourceId?: number, side: ArenaTagSide = ArenaTagSide.BOTH) {
+    this.turnCount = turnCount;
+    this.sourceMove = sourceMove;
+    this.sourceId = sourceId;
+    this.side = side;
+  }
 
   apply(_arena: Arena, _simulated: boolean, ..._args: unknown[]): boolean {
     return true;
@@ -72,9 +141,9 @@ export abstract class ArenaTag {
   /**
    * When given a arena tag or json representing one, load the data for it.
    * This is meant to be inherited from by any arena tag with custom attributes
-   * @param {ArenaTag | any} source An arena tag
+   * @param source - The {@linkcode BaseArenaTag} being loaded
    */
-  loadTag(source: ArenaTag | any): void {
+  loadTag(source: BaseArenaTag): void {
     this.turnCount = source.turnCount;
     this.sourceMove = source.sourceMove;
     this.sourceId = source.sourceId;
@@ -107,13 +176,21 @@ export abstract class ArenaTag {
   }
 }
 
+/**
+ * Abstract class for arena tags that can persist across turns.
+ */
+export abstract class SerializableArenaTag extends ArenaTag {
+  abstract readonly tagType: SerializableArenaTagType;
+}
+
 /**
  * Arena Tag class for {@link https://bulbapedia.bulbagarden.net/wiki/Mist_(move) Mist}.
  * Prevents Pokémon on the opposing side from lowering the stats of the Pokémon in the Mist.
  */
-export class MistTag extends ArenaTag {
+export class MistTag extends SerializableArenaTag {
-  constructor(turnCount: number, sourceId: number, side: ArenaTagSide) {
+  readonly tagType = ArenaTagType.MIST;
-    super(ArenaTagType.MIST, turnCount, MoveId.MIST, sourceId, side);
+  constructor(turnCount: number, sourceId: number | undefined, side: ArenaTagSide) {
+    super(turnCount, MoveId.MIST, sourceId, side);
   }
 
   onAdd(arena: Arena, quiet = false): void {
@@ -170,33 +247,11 @@ export class MistTag extends ArenaTag {
 
 /**
  * Reduces the damage of specific move categories in the arena.
- * @extends ArenaTag
  */
-export class WeakenMoveScreenTag extends ArenaTag {
+export abstract class WeakenMoveScreenTag extends SerializableArenaTag {
-  protected weakenedCategories: MoveCategory[];
+  public abstract readonly tagType: ArenaScreenTagType;
-
+  // Getter to avoid unnecessary serialization and prevent modification
-  /**
+  protected abstract get weakenedCategories(): MoveCategory[];
-   * Creates a new instance of the WeakenMoveScreenTag class.
-   *
-   * @param tagType - The type of the arena tag.
-   * @param turnCount - The number of turns the tag is active.
-   * @param sourceMove - The move that created the tag.
-   * @param sourceId - The ID of the source of the tag.
-   * @param side - The side (player or enemy) the tag affects.
-   * @param weakenedCategories - The categories of moves that are weakened by this tag.
-   */
-  constructor(
-    tagType: ArenaTagType,
-    turnCount: number,
-    sourceMove: MoveId,
-    sourceId: number,
-    side: ArenaTagSide,
-    weakenedCategories: MoveCategory[],
-  ) {
-    super(tagType, turnCount, sourceMove, sourceId, side);
-
-    this.weakenedCategories = weakenedCategories;
-  }
 
   /**
    * Applies the weakening effect to the move.
@@ -233,8 +288,13 @@ export class WeakenMoveScreenTag extends ArenaTag {
  * Used by {@linkcode MoveId.REFLECT}
  */
 class ReflectTag extends WeakenMoveScreenTag {
-  constructor(turnCount: number, sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.REFLECT;
-    super(ArenaTagType.REFLECT, turnCount, MoveId.REFLECT, sourceId, side, [MoveCategory.PHYSICAL]);
+  protected get weakenedCategories(): [MoveCategory.PHYSICAL] {
+    return [MoveCategory.PHYSICAL];
+  }
+
+  constructor(turnCount: number, sourceId: number | undefined, side: ArenaTagSide) {
+    super(turnCount, MoveId.REFLECT, sourceId, side);
   }
 
   onAdd(_arena: Arena, quiet = false): void {
@@ -253,8 +313,12 @@ class ReflectTag extends WeakenMoveScreenTag {
  * Used by {@linkcode MoveId.LIGHT_SCREEN}
  */
 class LightScreenTag extends WeakenMoveScreenTag {
-  constructor(turnCount: number, sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.LIGHT_SCREEN;
-    super(ArenaTagType.LIGHT_SCREEN, turnCount, MoveId.LIGHT_SCREEN, sourceId, side, [MoveCategory.SPECIAL]);
+  protected get weakenedCategories(): [MoveCategory.SPECIAL] {
+    return [MoveCategory.SPECIAL];
+  }
+  constructor(turnCount: number, sourceId: number | undefined, side: ArenaTagSide) {
+    super(turnCount, MoveId.LIGHT_SCREEN, sourceId, side);
   }
 
   onAdd(_arena: Arena, quiet = false): void {
@@ -273,11 +337,13 @@ class LightScreenTag extends WeakenMoveScreenTag {
  * Used by {@linkcode MoveId.AURORA_VEIL}
  */
 class AuroraVeilTag extends WeakenMoveScreenTag {
-  constructor(turnCount: number, sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.AURORA_VEIL;
-    super(ArenaTagType.AURORA_VEIL, turnCount, MoveId.AURORA_VEIL, sourceId, side, [
+  protected get weakenedCategories(): [MoveCategory.PHYSICAL, MoveCategory.SPECIAL] {
-      MoveCategory.SPECIAL,
+    return [MoveCategory.PHYSICAL, MoveCategory.SPECIAL];
-      MoveCategory.PHYSICAL,
+  }
-    ]);
+
+  constructor(turnCount: number, sourceId: number | undefined, side: ArenaTagSide) {
+    super(turnCount, MoveId.AURORA_VEIL, sourceId, side);
   }
 
   onAdd(_arena: Arena, quiet = false): void {
@@ -297,21 +363,23 @@ type ProtectConditionFunc = (arena: Arena, moveId: MoveId) => boolean;
  * Class to implement conditional team protection
  * applies protection based on the attributes of incoming moves
  */
-export class ConditionalProtectTag extends ArenaTag {
+export abstract class ConditionalProtectTag extends ArenaTag {
   /** The condition function to determine which moves are negated */
   protected protectConditionFunc: ProtectConditionFunc;
-  /** Does this apply to all moves, including those that ignore other forms of protection? */
+  /**
+   * Whether this protection effect should apply to _all_ moves, including ones that ignore other forms of protection.
+   * @defaultValue `false`
+   */
   protected ignoresBypass: boolean;
 
   constructor(
-    tagType: ArenaTagType,
     sourceMove: MoveId,
-    sourceId: number,
+    sourceId: number | undefined,
     side: ArenaTagSide,
     condition: ProtectConditionFunc,
     ignoresBypass = false,
   ) {
-    super(tagType, 1, sourceMove, sourceId, side);
+    super(1, sourceMove, sourceId, side);
 
     this.protectConditionFunc = condition;
     this.ignoresBypass = ignoresBypass;
@@ -397,8 +465,9 @@ const QuickGuardConditionFunc: ProtectConditionFunc = (_arena, moveId) => {
  * Condition: The incoming move has increased priority.
  */
 class QuickGuardTag extends ConditionalProtectTag {
-  constructor(sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.QUICK_GUARD;
-    super(ArenaTagType.QUICK_GUARD, MoveId.QUICK_GUARD, sourceId, side, QuickGuardConditionFunc);
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
+    super(MoveId.QUICK_GUARD, sourceId, side, QuickGuardConditionFunc);
   }
 }
 
@@ -428,8 +497,9 @@ const WideGuardConditionFunc: ProtectConditionFunc = (_arena, moveId): boolean =
  * can be an ally or enemy.
  */
 class WideGuardTag extends ConditionalProtectTag {
-  constructor(sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.WIDE_GUARD;
-    super(ArenaTagType.WIDE_GUARD, MoveId.WIDE_GUARD, sourceId, side, WideGuardConditionFunc);
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
+    super(MoveId.WIDE_GUARD, sourceId, side, WideGuardConditionFunc);
   }
 }
 
@@ -450,8 +520,9 @@ const MatBlockConditionFunc: ProtectConditionFunc = (_arena, moveId): boolean =>
  * Condition: The incoming move is a Physical or Special attack move.
  */
 class MatBlockTag extends ConditionalProtectTag {
-  constructor(sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.MAT_BLOCK;
-    super(ArenaTagType.MAT_BLOCK, MoveId.MAT_BLOCK, sourceId, side, MatBlockConditionFunc);
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
+    super(MoveId.MAT_BLOCK, sourceId, side, MatBlockConditionFunc);
   }
 
   onAdd(_arena: Arena) {
@@ -494,8 +565,9 @@ const CraftyShieldConditionFunc: ProtectConditionFunc = (_arena, moveId) => {
  * not target all Pokemon or sides of the field.
  */
 class CraftyShieldTag extends ConditionalProtectTag {
-  constructor(sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.CRAFTY_SHIELD;
-    super(ArenaTagType.CRAFTY_SHIELD, MoveId.CRAFTY_SHIELD, sourceId, side, CraftyShieldConditionFunc, true);
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
+    super(MoveId.CRAFTY_SHIELD, sourceId, side, CraftyShieldConditionFunc, true);
   }
 }
 
@@ -503,17 +575,8 @@ class CraftyShieldTag extends ConditionalProtectTag {
  * Arena Tag class for {@link https://bulbapedia.bulbagarden.net/wiki/Lucky_Chant_(move) Lucky Chant}.
  * Prevents critical hits against the tag's side.
  */
-export class NoCritTag extends ArenaTag {
+export class NoCritTag extends SerializableArenaTag {
-  /**
+  public readonly tagType = ArenaTagType.NO_CRIT;
-   * Constructor method for the NoCritTag class
-   * @param turnCount `number` the number of turns this effect lasts
-   * @param sourceMove {@linkcode MoveId} the move that created this effect
-   * @param sourceId `number` the ID of the {@linkcode Pokemon} that created this effect
-   * @param side {@linkcode ArenaTagSide} the side to which this effect belongs
-   */
-  constructor(turnCount: number, sourceMove: MoveId, sourceId: number, side: ArenaTagSide) {
-    super(ArenaTagType.NO_CRIT, turnCount, sourceMove, sourceId, side);
-  }
 
   /** Queues a message upon adding this effect to the field */
   onAdd(_arena: Arena): void {
@@ -545,13 +608,17 @@ export class NoCritTag extends ArenaTag {
  * Arena Tag class for {@link https://bulbapedia.bulbagarden.net/wiki/Wish_(move) | Wish}.
  * Heals the Pokémon in the user's position the turn after Wish is used.
  */
-class WishTag extends ArenaTag {
+class WishTag extends SerializableArenaTag {
-  private battlerIndex: BattlerIndex;
+  // The following fields are meant to be inwardly mutable, but outwardly immutable.
-  private triggerMessage: string;
+  readonly battlerIndex: BattlerIndex;
-  private healHp: number;
+  readonly healHp: number;
+  readonly sourceName: string;
+  // End inwardly mutable fields
 
-  constructor(turnCount: number, sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.WISH;
-    super(ArenaTagType.WISH, turnCount, MoveId.WISH, sourceId, side);
+
+  constructor(turnCount: number, sourceId: number | undefined, side: ArenaTagSide) {
+    super(turnCount, MoveId.WISH, sourceId, side);
   }
 
   onAdd(_arena: Arena): void {
@@ -561,45 +628,38 @@ class WishTag extends ArenaTag {
       return;
     }
 
-    super.onAdd(_arena);
+    (this as Mutable<this>).sourceName = getPokemonNameWithAffix(source);
-    this.healHp = toDmgValue(source.getMaxHp() / 2);
+    (this as Mutable<this>).healHp = toDmgValue(source.getMaxHp() / 2);
-
+    (this as Mutable<this>).battlerIndex = source.getBattlerIndex();
-    globalScene.phaseManager.queueMessage(
-      i18next.t("arenaTag:wishTagOnAdd", {
-        pokemonNameWithAffix: getPokemonNameWithAffix(source),
-      }),
-    );
   }
 
   onRemove(_arena: Arena): void {
     const target = globalScene.getField()[this.battlerIndex];
     if (target?.isActive(true)) {
-      globalScene.phaseManager.queueMessage(this.triggerMessage);
+      globalScene.phaseManager.queueMessage(
+        // TODO: Rename key as it triggers on activation
+        i18next.t("arenaTag:wishTagOnAdd", {
+          pokemonNameWithAffix: this.sourceName,
+        }),
+      );
       globalScene.phaseManager.unshiftNew("PokemonHealPhase", target.getBattlerIndex(), this.healHp, null, true, false);
     }
   }
+
+  override loadTag(source: NonFunctionProperties<WishTag>): void {
+    super.loadTag(source);
+    (this as Mutable<this>).battlerIndex = source.battlerIndex;
+    (this as Mutable<this>).healHp = source.healHp;
+    (this as Mutable<this>).sourceName = source.sourceName;
+  }
 }
 
 /**
  * Abstract class to implement weakened moves of a specific type.
  */
-export class WeakenMoveTypeTag extends ArenaTag {
+export abstract class WeakenMoveTypeTag extends SerializableArenaTag {
-  private weakenedType: PokemonType;
+  abstract readonly tagType: ArenaTagType.MUD_SPORT | ArenaTagType.WATER_SPORT;
-
+  abstract get weakenedType(): PokemonType;
-  /**
-   * Creates a new instance of the WeakenMoveTypeTag class.
-   *
-   * @param tagType - The type of the arena tag.
-   * @param turnCount - The number of turns the tag is active.
-   * @param type - The type being weakened from this tag.
-   * @param sourceMove - The move that created the tag.
-   * @param sourceId - The ID of the source of the tag.
-   */
-  constructor(tagType: ArenaTagType, turnCount: number, type: PokemonType, sourceMove: MoveId, sourceId: number) {
-    super(tagType, turnCount, sourceMove, sourceId);
-
-    this.weakenedType = type;
-  }
 
   /**
    * Reduces an attack's power by 0.33x if it matches this tag's weakened type.
@@ -623,8 +683,12 @@ export class WeakenMoveTypeTag extends ArenaTag {
  * Weakens Electric type moves for a set amount of turns, usually 5.
  */
 class MudSportTag extends WeakenMoveTypeTag {
-  constructor(turnCount: number, sourceId: number) {
+  public readonly tagType = ArenaTagType.MUD_SPORT;
-    super(ArenaTagType.MUD_SPORT, turnCount, PokemonType.ELECTRIC, MoveId.MUD_SPORT, sourceId);
+  override get weakenedType(): PokemonType.ELECTRIC {
+    return PokemonType.ELECTRIC;
+  }
+  constructor(turnCount: number, sourceId?: number) {
+    super(turnCount, MoveId.MUD_SPORT, sourceId);
   }
 
   onAdd(_arena: Arena): void {
@@ -641,8 +705,12 @@ class MudSportTag extends WeakenMoveTypeTag {
  * Weakens Fire type moves for a set amount of turns, usually 5.
  */
 class WaterSportTag extends WeakenMoveTypeTag {
-  constructor(turnCount: number, sourceId: number) {
+  public readonly tagType = ArenaTagType.WATER_SPORT;
-    super(ArenaTagType.WATER_SPORT, turnCount, PokemonType.FIRE, MoveId.WATER_SPORT, sourceId);
+  override get weakenedType(): PokemonType.FIRE {
+    return PokemonType.FIRE;
+  }
+  constructor(turnCount: number, sourceId?: number) {
+    super(turnCount, MoveId.WATER_SPORT, sourceId);
   }
 
   onAdd(_arena: Arena): void {
@@ -660,8 +728,9 @@ class WaterSportTag extends WeakenMoveTypeTag {
  * Converts Normal-type moves to Electric type for the rest of the turn.
  */
 export class IonDelugeTag extends ArenaTag {
+  public readonly tagType = ArenaTagType.ION_DELUGE;
   constructor(sourceMove?: MoveId) {
-    super(ArenaTagType.ION_DELUGE, 1, sourceMove);
+    super(1, sourceMove);
   }
 
   /** Queues an on-add message */
@@ -690,7 +759,8 @@ export class IonDelugeTag extends ArenaTag {
 /**
  * Abstract class to implement arena traps.
  */
-export class ArenaTrapTag extends ArenaTag {
+export abstract class ArenaTrapTag extends SerializableArenaTag {
+  abstract readonly tagType: ArenaTrapTagType;
   public layers: number;
   public maxLayers: number;
 
@@ -703,8 +773,8 @@ export class ArenaTrapTag extends ArenaTag {
    * @param side - The side (player or enemy) the tag affects.
    * @param maxLayers - The maximum amount of layers this tag can have.
    */
-  constructor(tagType: ArenaTagType, sourceMove: MoveId, sourceId: number, side: ArenaTagSide, maxLayers: number) {
+  constructor(sourceMove: MoveId, sourceId: number | undefined, side: ArenaTagSide, maxLayers: number) {
-    super(tagType, 0, sourceMove, sourceId, side);
+    super(0, sourceMove, sourceId, side);
 
     this.layers = 1;
     this.maxLayers = maxLayers;
@@ -743,7 +813,7 @@ export class ArenaTrapTag extends ArenaTag {
       : Phaser.Math.Linear(0, 1 / Math.pow(2, this.layers), Math.min(pokemon.getHpRatio(), 0.5) * 2);
   }
 
-  loadTag(source: any): void {
+  loadTag(source: NonFunctionProperties<ArenaTrapTag>): void {
     super.loadTag(source);
     this.layers = source.layers;
     this.maxLayers = source.maxLayers;
@@ -756,8 +826,9 @@ export class ArenaTrapTag extends ArenaTag {
  * in damage for 1, 2, or 3 layers of Spikes respectively if they are summoned into this trap.
  */
 class SpikesTag extends ArenaTrapTag {
-  constructor(sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.SPIKES;
-    super(ArenaTagType.SPIKES, MoveId.SPIKES, sourceId, side, 3);
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
+    super(MoveId.SPIKES, sourceId, side, 3);
   }
 
   onAdd(arena: Arena, quiet = false): void {
@@ -814,11 +885,12 @@ class SpikesTag extends ArenaTrapTag {
  * Pokémon summoned into this trap remove it entirely.
  */
 class ToxicSpikesTag extends ArenaTrapTag {
-  private neutralized: boolean;
+  #neutralized: boolean;
+  public readonly tagType = ArenaTagType.TOXIC_SPIKES;
 
-  constructor(sourceId: number, side: ArenaTagSide) {
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
-    super(ArenaTagType.TOXIC_SPIKES, MoveId.TOXIC_SPIKES, sourceId, side, 2);
+    super(MoveId.TOXIC_SPIKES, sourceId, side, 2);
-    this.neutralized = false;
+    this.#neutralized = false;
   }
 
   onAdd(arena: Arena, quiet = false): void {
@@ -844,7 +916,7 @@ class ToxicSpikesTag extends ArenaTrapTag {
   }
 
   onRemove(arena: Arena): void {
-    if (!this.neutralized) {
+    if (!this.#neutralized) {
       super.onRemove(arena);
     }
   }
@@ -855,7 +927,7 @@ class ToxicSpikesTag extends ArenaTrapTag {
         return true;
       }
       if (pokemon.isOfType(PokemonType.POISON)) {
-        this.neutralized = true;
+        this.#neutralized = true;
         if (globalScene.arena.removeTag(this.tagType)) {
           globalScene.phaseManager.queueMessage(
             i18next.t("arenaTag:toxicSpikesActivateTrapPoison", {
@@ -889,55 +961,15 @@ class ToxicSpikesTag extends ArenaTrapTag {
   }
 }
 
-/**
- * Arena Tag class for delayed attacks, such as {@linkcode MoveId.FUTURE_SIGHT} or {@linkcode MoveId.DOOM_DESIRE}.
- * Delays the attack's effect by a set amount of turns, usually 3 (including the turn the move is used),
- * and deals damage after the turn count is reached.
- */
-export class DelayedAttackTag extends ArenaTag {
-  public targetIndex: BattlerIndex;
-
-  constructor(
-    tagType: ArenaTagType,
-    sourceMove: MoveId | undefined,
-    sourceId: number,
-    targetIndex: BattlerIndex,
-    side: ArenaTagSide = ArenaTagSide.BOTH,
-  ) {
-    super(tagType, 3, sourceMove, sourceId, side);
-
-    this.targetIndex = targetIndex;
-    this.side = side;
-  }
-
-  lapse(arena: Arena): boolean {
-    const ret = super.lapse(arena);
-
-    if (!ret) {
-      // TODO: This should not add to move history (for Spite)
-      globalScene.phaseManager.unshiftNew(
-        "MoveEffectPhase",
-        this.sourceId!,
-        [this.targetIndex],
-        allMoves[this.sourceMove!],
-        MoveUseMode.FOLLOW_UP,
-      ); // TODO: are those bangs correct?
-    }
-
-    return ret;
-  }
-
-  onRemove(_arena: Arena): void {}
-}
-
 /**
  * Arena Tag class for {@link https://bulbapedia.bulbagarden.net/wiki/Stealth_Rock_(move) Stealth Rock}.
  * Applies up to 1 layer of Stealth Rocks, dealing percentage-based damage to any Pokémon
  * who is summoned into the trap, based on the Rock type's type effectiveness.
  */
 class StealthRockTag extends ArenaTrapTag {
-  constructor(sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.STEALTH_ROCK;
-    super(ArenaTagType.STEALTH_ROCK, MoveId.STEALTH_ROCK, sourceId, side, 1);
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
+    super(MoveId.STEALTH_ROCK, sourceId, side, 1);
   }
 
   onAdd(arena: Arena, quiet = false): void {
@@ -1025,8 +1057,9 @@ class StealthRockTag extends ArenaTrapTag {
  * to any Pokémon who is summoned into this trap.
  */
 class StickyWebTag extends ArenaTrapTag {
-  constructor(sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.STICKY_WEB;
-    super(ArenaTagType.STICKY_WEB, MoveId.STICKY_WEB, sourceId, side, 1);
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
+    super(MoveId.STICKY_WEB, sourceId, side, 1);
   }
 
   onAdd(arena: Arena, quiet = false): void {
@@ -1093,14 +1126,57 @@ class StickyWebTag extends ArenaTrapTag {
   }
 }
 
+/**
+ * Arena Tag class for delayed attacks, such as {@linkcode MoveId.FUTURE_SIGHT} or {@linkcode MoveId.DOOM_DESIRE}.
+ * Delays the attack's effect by a set amount of turns, usually 3 (including the turn the move is used),
+ * and deals damage after the turn count is reached.
+ */
+export class DelayedAttackTag extends SerializableArenaTag {
+  public targetIndex: BattlerIndex;
+  public readonly tagType: ArenaDelayedAttackTagType;
+
+  constructor(
+    tagType: ArenaTagType.DOOM_DESIRE | ArenaTagType.FUTURE_SIGHT,
+    sourceMove: MoveId | undefined,
+    sourceId: number | undefined,
+    targetIndex: BattlerIndex,
+    side: ArenaTagSide = ArenaTagSide.BOTH,
+  ) {
+    super(3, sourceMove, sourceId, side);
+    this.tagType = tagType;
+    this.targetIndex = targetIndex;
+    this.side = side;
+  }
+
+  lapse(arena: Arena): boolean {
+    const ret = super.lapse(arena);
+
+    if (!ret) {
+      // TODO: This should not add to move history (for Spite)
+      globalScene.phaseManager.unshiftNew(
+        "MoveEffectPhase",
+        this.sourceId!,
+        [this.targetIndex],
+        allMoves[this.sourceMove!],
+        MoveUseMode.FOLLOW_UP,
+      ); // TODO: are those bangs correct?
+    }
+
+    return ret;
+  }
+
+  onRemove(_arena: Arena): void {}
+}
+
 /**
  * Arena Tag class for {@link https://bulbapedia.bulbagarden.net/wiki/Trick_Room_(move) Trick Room}.
  * Reverses the Speed stats for all Pokémon on the field as long as this arena tag is up,
  * also reversing the turn order for all Pokémon on the field as well.
  */
-export class TrickRoomTag extends ArenaTag {
+export class TrickRoomTag extends SerializableArenaTag {
-  constructor(turnCount: number, sourceId: number) {
+  public readonly tagType = ArenaTagType.TRICK_ROOM;
-    super(ArenaTagType.TRICK_ROOM, turnCount, MoveId.TRICK_ROOM, sourceId);
+  constructor(turnCount: number, sourceId?: number) {
+    super(turnCount, MoveId.TRICK_ROOM, sourceId);
   }
 
   /**
@@ -1142,9 +1218,10 @@ export class TrickRoomTag extends ArenaTag {
  * Grounds all Pokémon on the field, including Flying-types and those with
  * {@linkcode AbilityId.LEVITATE} for the duration of the arena tag, usually 5 turns.
  */
-export class GravityTag extends ArenaTag {
+export class GravityTag extends SerializableArenaTag {
-  constructor(turnCount: number) {
+  public readonly tagType = ArenaTagType.GRAVITY;
-    super(ArenaTagType.GRAVITY, turnCount, MoveId.GRAVITY);
+  constructor(turnCount: number, sourceId?: number) {
+    super(turnCount, MoveId.GRAVITY, sourceId);
   }
 
   onAdd(_arena: Arena): void {
@@ -1170,9 +1247,10 @@ export class GravityTag extends ArenaTag {
  * Doubles the Speed of the Pokémon who created this arena tag, as well as all allied Pokémon.
  * Applies this arena tag for 4 turns (including the turn the move was used).
  */
-class TailwindTag extends ArenaTag {
+class TailwindTag extends SerializableArenaTag {
-  constructor(turnCount: number, sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.TAILWIND;
-    super(ArenaTagType.TAILWIND, turnCount, MoveId.TAILWIND, sourceId, side);
+  constructor(turnCount: number, sourceId: number | undefined, side: ArenaTagSide) {
+    super(turnCount, MoveId.TAILWIND, sourceId, side);
   }
 
   onAdd(_arena: Arena, quiet = false): void {
@@ -1238,9 +1316,10 @@ class TailwindTag extends ArenaTag {
  * Arena Tag class for {@link https://bulbapedia.bulbagarden.net/wiki/Happy_Hour_(move) Happy Hour}.
  * Doubles the prize money from trainers and money moves like {@linkcode MoveId.PAY_DAY} and {@linkcode MoveId.MAKE_IT_RAIN}.
  */
-class HappyHourTag extends ArenaTag {
+class HappyHourTag extends SerializableArenaTag {
-  constructor(turnCount: number, sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.HAPPY_HOUR;
-    super(ArenaTagType.HAPPY_HOUR, turnCount, MoveId.HAPPY_HOUR, sourceId, side);
+  constructor(turnCount: number, sourceId: number | undefined, side: ArenaTagSide) {
+    super(turnCount, MoveId.HAPPY_HOUR, sourceId, side);
   }
 
   onAdd(_arena: Arena): void {
@@ -1253,8 +1332,9 @@ class HappyHourTag extends ArenaTag {
 }
 
 class SafeguardTag extends ArenaTag {
-  constructor(turnCount: number, sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.SAFEGUARD;
-    super(ArenaTagType.SAFEGUARD, turnCount, MoveId.SAFEGUARD, sourceId, side);
+  constructor(turnCount: number, sourceId: number | undefined, side: ArenaTagSide) {
+    super(turnCount, MoveId.SAFEGUARD, sourceId, side);
   }
 
   onAdd(_arena: Arena): void {
@@ -1275,18 +1355,21 @@ class SafeguardTag extends ArenaTag {
 }
 
 class NoneTag extends ArenaTag {
+  public readonly tagType = ArenaTagType.NONE;
   constructor() {
-    super(ArenaTagType.NONE, 0);
+    super(0);
   }
 }
+
 /**
  * This arena tag facilitates the application of the move Imprison
  * Imprison remains in effect as long as the source Pokemon is active and present on the field.
  * Imprison will apply to any opposing Pokemon that switch onto the field as well.
  */
 class ImprisonTag extends ArenaTrapTag {
-  constructor(sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.IMPRISON;
-    super(ArenaTagType.IMPRISON, MoveId.IMPRISON, sourceId, side, 1);
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
+    super(MoveId.IMPRISON, sourceId, side, 1);
   }
 
   /**
@@ -1341,7 +1424,9 @@ class ImprisonTag extends ArenaTrapTag {
    */
   override onRemove(): void {
     const party = this.getAffectedPokemon();
-    party.forEach(p => p.removeTag(BattlerTagType.IMPRISON));
+    party.forEach(p => {
+      p.removeTag(BattlerTagType.IMPRISON);
+    });
   }
 }
 
@@ -1352,9 +1437,10 @@ class ImprisonTag extends ArenaTrapTag {
  * Damages all non-Fire-type Pokemon on the given side of the field at the end
  * of each turn for 4 turns.
  */
-class FireGrassPledgeTag extends ArenaTag {
+class FireGrassPledgeTag extends SerializableArenaTag {
-  constructor(sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.FIRE_GRASS_PLEDGE;
-    super(ArenaTagType.FIRE_GRASS_PLEDGE, 4, MoveId.FIRE_PLEDGE, sourceId, side);
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
+    super(4, MoveId.FIRE_PLEDGE, sourceId, side);
   }
 
   override onAdd(_arena: Arena): void {
@@ -1400,9 +1486,10 @@ class FireGrassPledgeTag extends ArenaTag {
  * Doubles the secondary effect chance of moves from Pokemon on the
  * given side of the field for 4 turns.
  */
-class WaterFirePledgeTag extends ArenaTag {
+class WaterFirePledgeTag extends SerializableArenaTag {
-  constructor(sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.WATER_FIRE_PLEDGE;
-    super(ArenaTagType.WATER_FIRE_PLEDGE, 4, MoveId.WATER_PLEDGE, sourceId, side);
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
+    super(4, MoveId.WATER_PLEDGE, sourceId, side);
   }
 
   override onAdd(_arena: Arena): void {
@@ -1434,9 +1521,10 @@ class WaterFirePledgeTag extends ArenaTag {
  * and {@link https://bulbapedia.bulbagarden.net/wiki/Water_Pledge_(move) | Water Pledge}.
  * Quarters the Speed of Pokemon on the given side of the field for 4 turns.
  */
-class GrassWaterPledgeTag extends ArenaTag {
+class GrassWaterPledgeTag extends SerializableArenaTag {
-  constructor(sourceId: number, side: ArenaTagSide) {
+  public readonly tagType = ArenaTagType.GRASS_WATER_PLEDGE;
-    super(ArenaTagType.GRASS_WATER_PLEDGE, 4, MoveId.GRASS_PLEDGE, sourceId, side);
+  constructor(sourceId: number | undefined, side: ArenaTagSide) {
+    super(4, MoveId.GRASS_PLEDGE, sourceId, side);
   }
 
   override onAdd(_arena: Arena): void {
@@ -1456,9 +1544,10 @@ class GrassWaterPledgeTag extends ArenaTag {
  * If a Pokémon that's on the field when Fairy Lock is used goes on to faint later in the same turn,
  * the Pokémon that replaces it will still be unable to switch out in the following turn.
  */
-export class FairyLockTag extends ArenaTag {
+export class FairyLockTag extends SerializableArenaTag {
-  constructor(turnCount: number, sourceId: number) {
+  public readonly tagType = ArenaTagType.FAIRY_LOCK;
-    super(ArenaTagType.FAIRY_LOCK, turnCount, MoveId.FAIRY_LOCK, sourceId);
+  constructor(turnCount: number, sourceId?: number) {
+    super(turnCount, MoveId.FAIRY_LOCK, sourceId);
   }
 
   onAdd(_arena: Arena): void {
@@ -1472,15 +1561,29 @@ export class FairyLockTag extends ArenaTag {
  * Keeps track of the number of pokemon on the field with Neutralizing Gas - If it drops to zero, the effect is ended and abilities are reactivated
  *
  * Additionally ends onLose abilities when it is activated
+ * @sealed
  */
-export class SuppressAbilitiesTag extends ArenaTag {
+export class SuppressAbilitiesTag extends SerializableArenaTag {
-  private sourceCount: number;
+  // Source count is allowed to be inwardly mutable, but outwardly immutable
-  private beingRemoved: boolean;
+  public readonly sourceCount: number;
+  public readonly tagType = ArenaTagType.NEUTRALIZING_GAS;
+  // Private field prevents field from appearing during serialization
+  /** Whether the tag is in the process of being removed */
+  #beingRemoved: boolean;
+  /** Whether the tag is in the process of being removed */
+  public get beingRemoved(): boolean {
+    return this.#beingRemoved;
+  }
 
-  constructor(sourceId: number) {
+  constructor(sourceId?: number) {
-    super(ArenaTagType.NEUTRALIZING_GAS, 0, undefined, sourceId);
+    super(0, undefined, sourceId);
     this.sourceCount = 1;
-    this.beingRemoved = false;
+    this.#beingRemoved = false;
+  }
+
+  public override loadTag(source: NonFunctionProperties<SuppressAbilitiesTag>): void {
+    super.loadTag(source);
+    (this as Mutable<this>).sourceCount = source.sourceCount;
   }
 
   public override onAdd(_arena: Arena): void {
@@ -1492,19 +1595,21 @@ export class SuppressAbilitiesTag extends ArenaTag {
         if (fieldPokemon && fieldPokemon.id !== pokemon.id) {
           // TODO: investigate whether we can just remove the foreach and call `applyAbAttrs` directly, providing
           // the appropriate attributes (preLEaveField and IllusionBreak)
-          [true, false].forEach(passive => applyOnLoseAbAttrs({ pokemon: fieldPokemon, passive }));
+          [true, false].forEach(passive => {
+            applyOnLoseAbAttrs({ pokemon: fieldPokemon, passive });
+          });
         }
       }
     }
   }
 
   public override onOverlap(_arena: Arena, source: Pokemon | null): void {
-    this.sourceCount++;
+    (this as Mutable<this>).sourceCount++;
     this.playActivationMessage(source);
   }
 
   public onSourceLeave(arena: Arena): void {
-    this.sourceCount--;
+    (this as Mutable<this>).sourceCount--;
     if (this.sourceCount <= 0) {
       arena.removeTag(ArenaTagType.NEUTRALIZING_GAS);
     } else if (this.sourceCount === 1) {
@@ -1522,7 +1627,7 @@ export class SuppressAbilitiesTag extends ArenaTag {
   }
 
   public override onRemove(_arena: Arena, quiet = false) {
-    this.beingRemoved = true;
+    this.#beingRemoved = true;
     if (!quiet) {
       globalScene.phaseManager.queueMessage(i18next.t("arenaTag:neutralizingGasOnRemove"));
     }
@@ -1530,7 +1635,9 @@ export class SuppressAbilitiesTag extends ArenaTag {
     for (const pokemon of globalScene.getField(true)) {
       // There is only one pokemon with this attr on the field on removal, so its abilities are already active
       if (pokemon && !pokemon.hasAbilityWithAttr("PreLeaveFieldRemoveSuppressAbilitiesSourceAbAttr", false)) {
-        [true, false].forEach(passive => applyOnGainAbAttrs({ pokemon, passive }));
+        [true, false].forEach(passive => {
+          applyOnGainAbAttrs({ pokemon, passive });
+        });
       }
     }
   }
@@ -1539,10 +1646,6 @@ export class SuppressAbilitiesTag extends ArenaTag {
     return this.sourceCount > 1;
   }
 
-  public isBeingRemoved() {
-    return this.beingRemoved;
-  }
-
   private playActivationMessage(pokemon: Pokemon | null) {
     if (pokemon) {
       globalScene.phaseManager.queueMessage(
@@ -1559,7 +1662,7 @@ export function getArenaTag(
   tagType: ArenaTagType,
   turnCount: number,
   sourceMove: MoveId | undefined,
-  sourceId: number,
+  sourceId: number | undefined,
   targetIndex?: BattlerIndex,
   side: ArenaTagSide = ArenaTagSide.BOTH,
 ): ArenaTag | null {
@@ -1575,7 +1678,7 @@ export function getArenaTag(
     case ArenaTagType.CRAFTY_SHIELD:
       return new CraftyShieldTag(sourceId, side);
     case ArenaTagType.NO_CRIT:
-      return new NoCritTag(turnCount, sourceMove!, sourceId, side); // TODO: is this bang correct?
+      return new NoCritTag(turnCount, sourceMove, sourceId, side);
     case ArenaTagType.MUD_SPORT:
       return new MudSportTag(turnCount, sourceId);
     case ArenaTagType.WATER_SPORT:
@@ -1588,7 +1691,10 @@ export function getArenaTag(
       return new ToxicSpikesTag(sourceId, side);
     case ArenaTagType.FUTURE_SIGHT:
     case ArenaTagType.DOOM_DESIRE:
-      return new DelayedAttackTag(tagType, sourceMove, sourceId, targetIndex!, side); // TODO:questionable bang
+      if (!targetIndex) {
+        return null; // If missing target index, no tag is created
+      }
+      return new DelayedAttackTag(tagType, sourceMove, sourceId, targetIndex, side);
     case ArenaTagType.WISH:
       return new WishTag(turnCount, sourceId, side);
     case ArenaTagType.STEALTH_ROCK:
@@ -1598,7 +1704,7 @@ export function getArenaTag(
     case ArenaTagType.TRICK_ROOM:
       return new TrickRoomTag(turnCount, sourceId);
     case ArenaTagType.GRAVITY:
-      return new GravityTag(turnCount);
+      return new GravityTag(turnCount, sourceId);
     case ArenaTagType.REFLECT:
       return new ReflectTag(turnCount, sourceId, side);
     case ArenaTagType.LIGHT_SCREEN:
@@ -1630,10 +1736,10 @@ export function getArenaTag(
 
 /**
  * When given a battler tag or json representing one, creates an actual ArenaTag object with the same data.
- * @param {ArenaTag | any} source An arena tag
+ * @param source - An arena tag
- * @return {ArenaTag} The valid arena tag
+ * @returns The valid arena tag
  */
-export function loadArenaTag(source: ArenaTag | any): ArenaTag {
+export function loadArenaTag(source: (ArenaTag | ArenaTagTypeData) & { targetIndex?: BattlerIndex }): ArenaTag {
   const tag =
     getArenaTag(
       source.tagType,
@@ -1646,3 +1752,37 @@ export function loadArenaTag(source: ArenaTag | any): ArenaTag {
   tag.loadTag(source);
   return tag;
 }
+
+export type ArenaTagTypeMap = {
+  [ArenaTagType.MUD_SPORT]: MudSportTag;
+  [ArenaTagType.WATER_SPORT]: WaterSportTag;
+  [ArenaTagType.ION_DELUGE]: IonDelugeTag;
+  [ArenaTagType.SPIKES]: SpikesTag;
+  [ArenaTagType.MIST]: MistTag;
+  [ArenaTagType.QUICK_GUARD]: QuickGuardTag;
+  [ArenaTagType.WIDE_GUARD]: WideGuardTag;
+  [ArenaTagType.MAT_BLOCK]: MatBlockTag;
+  [ArenaTagType.CRAFTY_SHIELD]: CraftyShieldTag;
+  [ArenaTagType.NO_CRIT]: NoCritTag;
+  [ArenaTagType.TOXIC_SPIKES]: ToxicSpikesTag;
+  [ArenaTagType.FUTURE_SIGHT]: DelayedAttackTag;
+  [ArenaTagType.DOOM_DESIRE]: DelayedAttackTag;
+  [ArenaTagType.WISH]: WishTag;
+  [ArenaTagType.STEALTH_ROCK]: StealthRockTag;
+  [ArenaTagType.STICKY_WEB]: StickyWebTag;
+  [ArenaTagType.TRICK_ROOM]: TrickRoomTag;
+  [ArenaTagType.GRAVITY]: GravityTag;
+  [ArenaTagType.REFLECT]: ReflectTag;
+  [ArenaTagType.LIGHT_SCREEN]: LightScreenTag;
+  [ArenaTagType.AURORA_VEIL]: AuroraVeilTag;
+  [ArenaTagType.TAILWIND]: TailwindTag;
+  [ArenaTagType.HAPPY_HOUR]: HappyHourTag;
+  [ArenaTagType.SAFEGUARD]: SafeguardTag;
+  [ArenaTagType.IMPRISON]: ImprisonTag;
+  [ArenaTagType.FIRE_GRASS_PLEDGE]: FireGrassPledgeTag;
+  [ArenaTagType.WATER_FIRE_PLEDGE]: WaterFirePledgeTag;
+  [ArenaTagType.GRASS_WATER_PLEDGE]: GrassWaterPledgeTag;
+  [ArenaTagType.FAIRY_LOCK]: FairyLockTag;
+  [ArenaTagType.NEUTRALIZING_GAS]: SuppressAbilitiesTag;
+  [ArenaTagType.NONE]: NoneTag;
+};

src/data/terrain.ts

@@ -13,6 +13,11 @@ export enum TerrainType {
   PSYCHIC,
 }
 
+export interface SerializedTerrain {
+  terrainType: TerrainType;
+  turnsLeft: number;
+}
+
 export class Terrain {
   public terrainType: TerrainType;
   public turnsLeft: number;

src/data/weather.ts

@@ -11,6 +11,11 @@ import type { Move } from "#moves/move";
 import { randSeedInt } from "#utils/common";
 import i18next from "i18next";
 
+export interface SerializedWeather {
+  weatherType: WeatherType;
+  turnsLeft: number;
+}
+
 export class Weather {
   public weatherType: WeatherType;
   public turnsLeft: number;

src/enums/arena-tag-type.ts

@@ -1,3 +1,13 @@
+import type { ArenaTagTypeMap } from "#data/arena-tag";
+import type { NonSerializableArenaTagType, SerializableArenaTagType } from "#types/arena-tags";
+
+/**
+ * Enum representing all different types of {@linkcode ArenaTag}s.
+ * @privateRemarks
+ * ⚠️ When modifying the fields in this enum, ensure that:
+ * - The entry is added to / removed from {@linkcode ArenaTagTypeMap} 
+ * - The tag is added to / removed from {@linkcode NonSerializableArenaTagType} or {@linkcode SerializableArenaTagType}
+*/
 export enum ArenaTagType {
   NONE = "NONE",
   MUD_SPORT = "MUD_SPORT",

src/field/arena.ts

@@ -30,6 +30,7 @@ import { TagAddedEvent, TagRemovedEvent, TerrainChangedEvent, WeatherChangedEven
 import type { Pokemon } from "#field/pokemon";
 import { FieldEffectModifier } from "#modifiers/modifier";
 import type { Move } from "#moves/move";
+import type { AbstractConstructor } from "#types/type-helpers";
 import { type Constructor, isNullOrUndefined, NumberHolder, randSeedInt } from "#utils/common";
 import { getPokemonSpecies } from "#utils/pokemon-utils";
 
@@ -644,7 +645,7 @@ export class Arena {
    * @param args array of parameters that the called upon tags may need
    */
   applyTagsForSide(
-    tagType: ArenaTagType | Constructor<ArenaTag>,
+    tagType: ArenaTagType | Constructor<ArenaTag> | AbstractConstructor<ArenaTag>,
     side: ArenaTagSide,
     simulated: boolean,
     ...args: unknown[]
@@ -666,7 +667,11 @@ export class Arena {
    * @param simulated if `true`, this applies arena tags without changing game state
    * @param args array of parameters that the called upon tags may need
    */
-  applyTags(tagType: ArenaTagType | Constructor<ArenaTag>, simulated: boolean, ...args: unknown[]): void {
+  applyTags(
+    tagType: ArenaTagType | Constructor<ArenaTag> | AbstractConstructor<ArenaTag>,
+    simulated: boolean,
+    ...args: unknown[]
+  ): void {
     this.applyTagsForSide(tagType, ArenaTagSide.BOTH, simulated, ...args);
   }
 
@@ -723,7 +728,7 @@ export class Arena {
    * @param tagType The {@linkcode ArenaTagType} or {@linkcode ArenaTag} to get
    * @returns either the {@linkcode ArenaTag}, or `undefined` if it isn't there
    */
-  getTag(tagType: ArenaTagType | Constructor<ArenaTag>): ArenaTag | undefined {
+  getTag(tagType: ArenaTagType | Constructor<ArenaTag> | AbstractConstructor<ArenaTag>): ArenaTag | undefined {
     return this.getTagOnSide(tagType, ArenaTagSide.BOTH);
   }
 
@@ -739,7 +744,10 @@ export class Arena {
    * @param side The {@linkcode ArenaTagSide} to look at
    * @returns either the {@linkcode ArenaTag}, or `undefined` if it isn't there
    */
-  getTagOnSide(tagType: ArenaTagType | Constructor<ArenaTag>, side: ArenaTagSide): ArenaTag | undefined {
+  getTagOnSide(
+    tagType: ArenaTagType | Constructor<ArenaTag> | AbstractConstructor<ArenaTag>,
+    side: ArenaTagSide,
+  ): ArenaTag | undefined {
     return typeof tagType === "string"
       ? this.tags.find(
           t => t.tagType === tagType && (side === ArenaTagSide.BOTH || t.side === ArenaTagSide.BOTH || t.side === side),

src/field/pokemon.ts

@@ -2192,7 +2192,7 @@ export abstract class Pokemon extends Phaser.GameObjects.Container {
     }
     const suppressAbilitiesTag = arena.getTag(ArenaTagType.NEUTRALIZING_GAS) as SuppressAbilitiesTag;
     const suppressOffField = ability.hasAttr("PreSummonAbAttr");
-    if ((this.isOnField() || suppressOffField) && suppressAbilitiesTag && !suppressAbilitiesTag.isBeingRemoved()) {
+    if ((this.isOnField() || suppressOffField) && suppressAbilitiesTag && !suppressAbilitiesTag.beingRemoved) {
       const thisAbilitySuppressing = ability.hasAttr("PreLeaveFieldRemoveSuppressAbilitiesSourceAbAttr");
       const hasSuppressingAbility = this.hasAbilityWithAttr("PreLeaveFieldRemoveSuppressAbilitiesSourceAbAttr", false);
       // Neutralizing gas is up - suppress abilities unless they are unsuppressable or this pokemon is responsible for the gas

src/system/arena-data.ts

@@ -1,9 +1,19 @@
 import type { ArenaTag } from "#data/arena-tag";
-import { loadArenaTag } from "#data/arena-tag";
+import { loadArenaTag, SerializableArenaTag } from "#data/arena-tag";
 import { Terrain } from "#data/terrain";
 import { Weather } from "#data/weather";
 import type { BiomeId } from "#enums/biome-id";
 import { Arena } from "#field/arena";
+import type { ArenaTagTypeData } from "#types/arena-tags";
+import type { NonFunctionProperties } from "#types/type-helpers";
+
+export interface SerializedArenaData {
+  biome: BiomeId;
+  weather: NonFunctionProperties<Weather> | null;
+  terrain: NonFunctionProperties<Terrain> | null;
+  tags?: ArenaTagTypeData[];
+  playerTerasUsed?: number;
+}
 
 export class ArenaData {
   public biome: BiomeId;
@@ -12,24 +22,26 @@ export class ArenaData {
   public tags: ArenaTag[];
   public playerTerasUsed: number;
 
-  constructor(source: Arena | any) {
+  constructor(source: Arena | SerializedArenaData) {
-    const sourceArena = source instanceof Arena ? (source as Arena) : null;
+    // Exclude any unserializable tags from the serialized data (such as ones only lasting 1 turn).
-    this.biome = sourceArena ? sourceArena.biomeType : source.biome;
+    // NOTE: The filter has to be done _after_ map, data loaded from `ArenaTagTypeData`
-    this.weather = sourceArena
+    // is not yet an instance of `ArenaTag`
-      ? sourceArena.weather
+    this.tags =
-      : source.weather
+      source.tags
-        ? new Weather(source.weather.weatherType, source.weather.turnsLeft)
+        ?.map((t: ArenaTag | ArenaTagTypeData) => loadArenaTag(t))
-        : null;
+        ?.filter((tag): tag is SerializableArenaTag => tag instanceof SerializableArenaTag) ?? [];
-    this.terrain = sourceArena
-      ? sourceArena.terrain
-      : source.terrain
-        ? new Terrain(source.terrain.terrainType, source.terrain.turnsLeft)
-        : null;
-    this.playerTerasUsed = (sourceArena ? sourceArena.playerTerasUsed : source.playerTerasUsed) ?? 0;
-    this.tags = [];
 
-    if (source.tags) {
+    this.playerTerasUsed = source.playerTerasUsed ?? 0;
-      this.tags = source.tags.map(t => loadArenaTag(t));
+
+    if (source instanceof Arena) {
+      this.biome = source.biomeType;
+      this.weather = source.weather;
+      this.terrain = source.terrain;
+      return;
     }
+
+    this.biome = source.biome;
+    this.weather = source.weather ? new Weather(source.weather.weatherType, source.weather.turnsLeft) : null;
+    this.terrain = source.terrain ? new Terrain(source.terrain.terrainType, source.terrain.turnsLeft) : null;
   }
 }

src/system/game-data.ts

@@ -42,7 +42,7 @@ import * as Modifier from "#modifiers/modifier";
 import { MysteryEncounterSaveData } from "#mystery-encounters/mystery-encounter-save-data";
 import type { Variant } from "#sprites/variant";
 import { achvs } from "#system/achv";
-import { ArenaData } from "#system/arena-data";
+import { ArenaData, type SerializedArenaData } from "#system/arena-data";
 import { ChallengeData } from "#system/challenge-data";
 import { EggData } from "#system/egg-data";
 import { GameStats } from "#system/game-stats";
@@ -1286,7 +1286,7 @@ export class GameData {
         }
 
         case "arena":
-          return new ArenaData(v);
+          return new ArenaData(v as SerializedArenaData);
 
         case "challenges": {
           const ret: ChallengeData[] = [];