[Refactor] Re-implement save migration system (#5634)

package-lock.json

@@ -10,6 +10,7 @@
       "hasInstallScript": true,
       "dependencies": {
         "@material/material-color-utilities": "^0.2.7",
+        "compare-versions": "^6.1.1",
         "crypto-js": "^4.2.0",
         "i18next": "^24.2.2",
         "i18next-browser-languagedetector": "^8.0.4",
@@ -3605,6 +3606,12 @@
         "node": ">=18"
       }
     },
+    "node_modules/compare-versions": {
+      "version": "6.1.1",
+      "resolved": "https://registry.npmjs.org/compare-versions/-/compare-versions-6.1.1.tgz",
+      "integrity": "sha512-4hm4VPpIecmlg59CHXnRDnqGplJFrbLG4aFEl5vl6cK1u76ws3LLvX7ikFnTDl5vo39sjWD6AaDPYodJp/NNHg==",
+      "license": "MIT"
+    },
     "node_modules/concat-map": {
       "version": "0.0.1",
       "resolved": "https://registry.npmjs.org/concat-map/-/concat-map-0.0.1.tgz",

package.json

@@ -55,6 +55,7 @@
   },
   "dependencies": {
     "@material/material-color-utilities": "^0.2.7",
+    "compare-versions": "^6.1.1",
     "crypto-js": "^4.2.0",
     "i18next": "^24.2.2",
     "i18next-browser-languagedetector": "^8.0.4",

src/@types/SessionSaveMigrator.ts

@@ -0,0 +1,6 @@
+import type { SessionSaveData } from "#app/system/game-data";
+
+export interface SessionSaveMigrator {
+  version: string;
+  migrate: (data: SessionSaveData) => void;
+}

src/@types/SettingsSaveMigrator.ts

@@ -0,0 +1,5 @@
+export interface SettingsSaveMigrator {
+  version: string;
+  // biome-ignore lint/complexity/noBannedTypes: TODO - refactor settings
+  migrate: (data: Object) => void;
+}

src/@types/SystemSaveMigrator.ts

@@ -0,0 +1,6 @@
+import type { SystemSaveData } from "#app/system/game-data";
+
+export interface SystemSaveMigrator {
+  version: string;
+  migrate: (data: SystemSaveData) => void;
+}

src/system/version_migration/version_converter.ts

@@ -1,19 +1,104 @@
-import type { SessionSaveData, SystemSaveData } from "../game-data";
+import type { SessionSaveMigrator } from "#app/@types/SessionSaveMigrator";
+import type { SettingsSaveMigrator } from "#app/@types/SettingsSaveMigrator";
+import type { SystemSaveMigrator } from "#app/@types/SystemSaveMigrator";
+import type { SessionSaveData, SystemSaveData } from "#app/system/game-data";
+import { compareVersions } from "compare-versions";
 import { version } from "../../../package.json";
 
+/*
+// template for save migrator creation
+// versions/vA_B_C.ts
+
+// The version for each migrator should match the filename, ie: `vA_B_C.ts` -> `version: "A.B.C"
+// This is the target version (aka the version we're ending up on after the migrators are run)
+
+// The name for each migrator should match its purpose. For example, if you're fixing
+// the ability index of a pokemon, it might be called `migratePokemonAbilityIndex`
+
+const systemMigratorA: SystemSaveMigrator = {
+  version: "A.B.C",
+  migrate: (data: SystemSaveData): void => {
+    // migration code goes here
+  },
+};
+
+export const systemMigrators: Readonly<SystemSaveMigrator[]> = [systemMigratorA] as const;
+
+const sessionMigratorA: SessionSaveMigrator = {
+  version: "A.B.C",
+  migrate: (data: SessionSaveData): void => {
+    // migration code goes here
+  },
+};
+
+export const sessionMigrators: Readonly<SessionSaveMigrator[]> = [sessionMigratorA] as const;
+
+const settingsMigratorA: SettingsSaveMigrator = {
+  version: "A.B.C",
+  // biome-ignore lint/complexity/noBannedTypes: TODO - refactor settings
+  migrate: (data: Object): void => {
+    // migration code goes here
+  },
+};
+
+export const settingsMigrators: Readonly<SettingsSaveMigrator[]> = [settingsMigratorA] as const;
+*/
+
+// --- vA.B.C PATCHES --- //
+// import * as vA_B_C from "./versions/vA_B_C";
+
 // --- v1.0.4 (and below) PATCHES --- //
 import * as v1_0_4 from "./versions/v1_0_4";
 
-// --- v1.1.0 PATCHES --- //
-import * as v1_1_0 from "./versions/v1_1_0";
-
 // --- v1.7.0 PATCHES --- //
 import * as v1_7_0 from "./versions/v1_7_0";
 
 // --- v1.8.3 PATCHES --- //
 import * as v1_8_3 from "./versions/v1_8_3";
 
-const LATEST_VERSION = version.split(".").map(value => Number.parseInt(value));
+/** Current game version */
+const LATEST_VERSION = version;
+
+type SaveMigrator = SystemSaveMigrator | SessionSaveMigrator | SettingsSaveMigrator;
+
+// biome-ignore lint/complexity/noBannedTypes: TODO - refactor settings
+type SaveData = SystemSaveData | SessionSaveData | Object;
+
+// To add a new set of migrators, create a new `.push()` line like so:
+// `systemMigrators.push(...vA_B_C.systemMigrators);`
+
+/** All system save migrators */
+const systemMigrators: SystemSaveMigrator[] = [];
+systemMigrators.push(...v1_0_4.systemMigrators);
+systemMigrators.push(...v1_7_0.systemMigrators);
+systemMigrators.push(...v1_8_3.systemMigrators);
+
+/** All session save migrators */
+const sessionMigrators: SessionSaveMigrator[] = [];
+sessionMigrators.push(...v1_0_4.sessionMigrators);
+sessionMigrators.push(...v1_7_0.sessionMigrators);
+
+/** All settings migrators */
+const settingsMigrators: SettingsSaveMigrator[] = [];
+settingsMigrators.push(...v1_0_4.settingsMigrators);
+
+/** Sorts migrators by their stated version, ensuring they are applied in order from oldest to newest */
+const sortMigrators = (migrators: SaveMigrator[]): void => {
+  migrators.sort((a, b) => compareVersions(a.version, b.version));
+};
+
+sortMigrators(systemMigrators);
+sortMigrators(sessionMigrators);
+sortMigrators(settingsMigrators);
+
+const applyMigrators = (migrators: readonly SaveMigrator[], data: SaveData, saveVersion: string) => {
+  for (const migrator of migrators) {
+    const isMigratorVersionHigher = compareVersions(saveVersion, migrator.version) === -1;
+    if (isMigratorVersionHigher) {
+      migrator.migrate(data as any);
+    }
+  }
+};
 
 /**
  * Converts incoming {@linkcode SystemSaveData} that has a version below the
@@ -26,12 +111,12 @@ const LATEST_VERSION = version.split(".").map(value => Number.parseInt(value));
  * @see {@link SystemVersionConverter}
  */
 export function applySystemVersionMigration(data: SystemSaveData) {
-  const curVersion = data.gameVersion.split(".").map(value => Number.parseInt(value));
+  const prevVersion = data.gameVersion;
+  const isCurrentVersionHigher = compareVersions(prevVersion, LATEST_VERSION) === -1;
 
-  if (!curVersion.every((value, index) => value === LATEST_VERSION[index])) {
+  if (isCurrentVersionHigher) {
-    const converter = new SystemVersionConverter();
+    applyMigrators(systemMigrators, data, prevVersion);
-    converter.applyStaticPreprocessors(data);
+    console.log(`System data successfully migrated to v${LATEST_VERSION}!`);
-    converter.applyMigration(data, curVersion);
   }
 }
 
@@ -46,12 +131,15 @@ export function applySystemVersionMigration(data: SystemSaveData) {
  * @see {@link SessionVersionConverter}
  */
 export function applySessionVersionMigration(data: SessionSaveData) {
-  const curVersion = data.gameVersion.split(".").map(value => Number.parseInt(value));
+  const prevVersion = data.gameVersion;
+  const isCurrentVersionHigher = compareVersions(prevVersion, LATEST_VERSION) === -1;
 
-  if (!curVersion.every((value, index) => value === LATEST_VERSION[index])) {
+  if (isCurrentVersionHigher) {
-    const converter = new SessionVersionConverter();
+    // Always sanitize money as a safeguard
-    converter.applyStaticPreprocessors(data);
+    data.money = Math.floor(data.money);
-    converter.applyMigration(data, curVersion);
+
+    applyMigrators(sessionMigrators, data, prevVersion);
+    console.log(`Session data successfully migrated to v${LATEST_VERSION}!`);
   }
 }
 
@@ -65,156 +153,13 @@ export function applySessionVersionMigration(data: SessionSaveData) {
  * @param data Settings data object
  * @see {@link SettingsVersionConverter}
  */
+// biome-ignore lint/complexity/noBannedTypes: TODO - refactor settings
 export function applySettingsVersionMigration(data: Object) {
-  const gameVersion: string = data.hasOwnProperty("gameVersion") ? data["gameVersion"] : "1.0.0";
+  const prevVersion: string = data.hasOwnProperty("gameVersion") ? data["gameVersion"] : "1.0.0";
-  const curVersion = gameVersion.split(".").map(value => Number.parseInt(value));
+  const isCurrentVersionHigher = compareVersions(prevVersion, LATEST_VERSION) === -1;
 
-  if (!curVersion.every((value, index) => value === LATEST_VERSION[index])) {
+  if (isCurrentVersionHigher) {
-    const converter = new SettingsVersionConverter();
+    applyMigrators(settingsMigrators, data, prevVersion);
-    converter.applyStaticPreprocessors(data);
+    console.log(`Settings successfully migrated to v${LATEST_VERSION}!`);
-    converter.applyMigration(data, curVersion);
-  }
-}
-
-/**
- * Abstract class encapsulating the logic for migrating data from a given version up to
- * the current version listed in `package.json`.
- *
- * Note that, for any version converter, the corresponding `applyMigration`
- * function would only need to be changed once when the first migration for a
- * given version is introduced. Similarly, a version file (within the `versions`
- * folder) would only need to be created for a version once with the appropriate
- * array nomenclature.
- */
-abstract class VersionConverter {
-  /**
-   * Iterates through an array of designated migration functions that are each
-   * called one by one to transform the data.
-   * @param data The data to be operated on
-   * @param migrationArr An array of functions that will transform the incoming data
-   */
-  callMigrators(data: any, migrationArr: readonly any[]) {
-    for (const migrate of migrationArr) {
-      migrate(data);
-    }
-  }
-
-  /**
-   * Applies any version-agnostic data sanitation as defined within the function
-   * body.
-   * @param data The data to be operated on
-   */
-  applyStaticPreprocessors(_data: any): void {}
-
-  /**
-   * Uses the current version the incoming data to determine the starting point
-   * of the migration which will cascade up to the latest version, calling the
-   * necessary migration functions in the process.
-   * @param data The data to be operated on
-   * @param curVersion [0] Current major version
-   *                   [1] Current minor version
-   *                   [2] Current patch version
-   */
-  abstract applyMigration(data: any, curVersion: number[]): void;
-}
-
-/**
- * Class encapsulating the logic for migrating {@linkcode SessionSaveData} from
- * a given version up to the current version listed in `package.json`.
- * @extends VersionConverter
- */
-class SessionVersionConverter extends VersionConverter {
-  override applyStaticPreprocessors(data: SessionSaveData): void {
-    // Always sanitize money as a safeguard
-    data.money = Math.floor(data.money);
-  }
-
-  override applyMigration(data: SessionSaveData, curVersion: number[]): void {
-    const [curMajor, curMinor, curPatch] = curVersion;
-
-    if (curMajor === 1) {
-      if (curMinor === 0) {
-        if (curPatch <= 5) {
-          console.log("Applying v1.0.4 session data migration!");
-          this.callMigrators(data, v1_0_4.sessionMigrators);
-        }
-      }
-      if (curMinor <= 1) {
-        console.log("Applying v1.1.0 session data migration!");
-        this.callMigrators(data, v1_1_0.sessionMigrators);
-      }
-      if (curMinor < 7) {
-        console.log("Applying v1.7.0 session data migration!");
-        this.callMigrators(data, v1_7_0.sessionMigrators);
-      }
-    }
-
-    console.log(`Session data successfully migrated to v${version}!`);
-  }
-}
-
-/**
- * Class encapsulating the logic for migrating {@linkcode SystemSaveData} from
- * a given version up to the current version listed in `package.json`.
- * @extends VersionConverter
- */
-class SystemVersionConverter extends VersionConverter {
-  override applyMigration(data: SystemSaveData, curVersion: number[]): void {
-    const [curMajor, curMinor, curPatch] = curVersion;
-
-    if (curMajor === 1) {
-      if (curMinor === 0) {
-        if (curPatch <= 4) {
-          console.log("Applying v1.0.4 system data migraton!");
-          this.callMigrators(data, v1_0_4.systemMigrators);
-        }
-      }
-      if (curMinor <= 1) {
-        console.log("Applying v1.1.0 system data migraton!");
-        this.callMigrators(data, v1_1_0.systemMigrators);
-      }
-      if (curMinor < 7) {
-        console.log("Applying v1.7.0 system data migration!");
-        this.callMigrators(data, v1_7_0.systemMigrators);
-      }
-      if (curMinor === 8) {
-        if (curPatch <= 2) {
-          console.log("Applying v1.8.3 system data migration!");
-          this.callMigrators(data, v1_8_3.systemMigrators);
-        }
-      }
-    }
-
-    console.log(`System data successfully migrated to v${version}!`);
-  }
-}
-
-/**
- * Class encapsulating the logic for migrating settings data from
- * a given version up to the current version listed in `package.json`.
- * @extends VersionConverter
- */
-class SettingsVersionConverter extends VersionConverter {
-  override applyMigration(data: Object, curVersion: number[]): void {
-    const [curMajor, curMinor, curPatch] = curVersion;
-
-    if (curMajor === 1) {
-      if (curMinor === 0) {
-        if (curPatch <= 4) {
-          console.log("Applying v1.0.4 settings data migraton!");
-          this.callMigrators(data, v1_0_4.settingsMigrators);
-        }
-      }
-      if (curMinor <= 1) {
-        console.log("Applying v1.1.0 settings data migraton!");
-        this.callMigrators(data, v1_1_0.settingsMigrators);
-      }
-      if (curMinor < 7) {
-        console.log("Applying v1.7.0 settings data migration!");
-        this.callMigrators(data, v1_7_0.settingsMigrators);
-      }
-    }
-
-    console.log(`Settings data successfully migrated to v${version}!`);
   }
 }

src/system/version_migration/versions/v1_0_4.ts

@@ -4,15 +4,18 @@ import { AbilityAttr, defaultStarterSpecies, DexAttr } from "#app/system/game-da
 import { allSpecies } from "#app/data/pokemon-species";
 import { CustomPokemonData } from "#app/data/custom-pokemon-data";
 import { isNullOrUndefined } from "#app/utils";
+import type { SystemSaveMigrator } from "#app/@types/SystemSaveMigrator";
+import type { SettingsSaveMigrator } from "#app/@types/SettingsSaveMigrator";
+import type { SessionSaveMigrator } from "#app/@types/SessionSaveMigrator";
 
-export const systemMigrators = [
+/**
-  /**
+ * Migrate ability starter data if empty for caught species.
-   * Migrate ability starter data if empty for caught species.
+ * @param data - {@linkcode SystemSaveData}
-   * @param data {@linkcode SystemSaveData}
+ */
-   */
+const migrateAbilityData: SystemSaveMigrator = {
-  function migrateAbilityData(data: SystemSaveData) {
+  version: "1.0.4",
+  migrate: (data: SystemSaveData): void => {
     if (data.starterData && data.dexData) {
-      // biome-ignore lint/complexity/noForEach: <explanation>
       Object.keys(data.starterData).forEach(sd => {
         if (data.dexData[sd]?.caughtAttr && data.starterData[sd] && !data.starterData[sd].abilityAttr) {
           data.starterData[sd].abilityAttr = 1;
@@ -20,12 +23,15 @@ export const systemMigrators = [
       });
     }
   },
+};
 
-  /**
+/**
-   * Populate legendary Pokémon statistics if they are missing.
+ * Populate legendary Pokémon statistics if they are missing.
-   * @param data {@linkcode SystemSaveData}
+ * @param data - {@linkcode SystemSaveData}
-   */
+ */
-  function fixLegendaryStats(data: SystemSaveData) {
+const fixLegendaryStats: SystemSaveMigrator = {
+  version: "1.0.4",
+  migrate: (data: SystemSaveData): void => {
     if (
       data.gameStats &&
       data.gameStats.legendaryPokemonCaught !== undefined &&
@@ -34,7 +40,6 @@ export const systemMigrators = [
       data.gameStats.subLegendaryPokemonSeen = 0;
       data.gameStats.subLegendaryPokemonCaught = 0;
       data.gameStats.subLegendaryPokemonHatched = 0;
-      // biome-ignore lint/complexity/noForEach: <explanation>
       allSpecies
         .filter(s => s.subLegendary)
         .forEach(s => {
@@ -66,12 +71,15 @@ export const systemMigrators = [
       );
     }
   },
+};
 
-  /**
+/**
-   * Unlock all starters' first ability and female gender option.
+ * Unlock all starters' first ability and female gender option.
-   * @param data {@linkcode SystemSaveData}
+ * @param data - {@linkcode SystemSaveData}
-   */
+ */
-  function fixStarterData(data: SystemSaveData) {
+const fixStarterData: SystemSaveMigrator = {
+  version: "1.0.4",
+  migrate: (data: SystemSaveData): void => {
     if (!isNullOrUndefined(data.starterData)) {
       for (const starterId of defaultStarterSpecies) {
         if (data.starterData[starterId]?.abilityAttr) {
@@ -83,17 +91,22 @@ export const systemMigrators = [
       }
     }
   },
+};
+
+export const systemMigrators: Readonly<SystemSaveMigrator[]> = [
+  migrateAbilityData,
+  fixLegendaryStats,
+  fixStarterData,
 ] as const;
 
-export const settingsMigrators = [
+/**
-  /**
+ * Migrate from `REROLL_TARGET` property to {@linkcode SettingKeys.Shop_Cursor_Target}
-   * Migrate from "REROLL_TARGET" property to {@linkcode
+ * @param data - The `settings` object
-   * SettingKeys.Shop_Cursor_Target}.
+ */
-   * @param data the `settings` object
+const fixRerollTarget: SettingsSaveMigrator = {
-   */
+  version: "1.0.4",
-
+  // biome-ignore lint/complexity/noBannedTypes: TODO - refactor settings
-  // biome-ignore lint/complexity/noBannedTypes: TODO: fix the type to not be object...
+  migrate: (data: Object): void => {
-  function fixRerollTarget(data: Object) {
     if (data.hasOwnProperty("REROLL_TARGET") && !data.hasOwnProperty(SettingKeys.Shop_Cursor_Target)) {
       data[SettingKeys.Shop_Cursor_Target] = data["REROLL_TARGET"];
       // biome-ignore lint/performance/noDelete: intentional
@@ -101,16 +114,20 @@ export const settingsMigrators = [
       localStorage.setItem("settings", JSON.stringify(data));
     }
   },
-] as const;
+};
 
-export const sessionMigrators = [
+export const settingsMigrators: Readonly<SettingsSaveMigrator[]> = [fixRerollTarget] as const;
-  /**
+
-   *  Converts old lapsing modifiers (battle items, lures, and Dire Hit) and
+/**
-   *  other miscellaneous modifiers (vitamins, White Herb) to any new class
+ *  Converts old lapsing modifiers (battle items, lures, and Dire Hit) and
-   *  names and/or change in reload arguments.
+ *  other miscellaneous modifiers (vitamins, White Herb) to any new class
-   *  @param data {@linkcode SessionSaveData}
+ *  names and/or change in reload arguments.
-   */
+ *  @param data - {@linkcode SessionSaveData}
-  function migrateModifiers(data: SessionSaveData) {
+ */
+const migrateModifiers: SessionSaveMigrator = {
+  version: "1.0.4",
+  // biome-ignore lint/complexity/noExcessiveCognitiveComplexity: necessary?
+  migrate: (data: SessionSaveData): void => {
     for (const m of data.modifiers) {
       if (m.className === "PokemonBaseStatModifier") {
         m.className = "BaseStatModifier";
@@ -163,12 +180,11 @@ export const sessionMigrators = [
       }
     }
   },
-  /**
+};
-   *  Converts old Pokemon natureOverride and mysteryEncounterData
+
-   *  to use the new conjoined {@linkcode Pokemon.customPokemonData} structure instead.
+const migrateCustomPokemonData: SessionSaveMigrator = {
-   *  @param data {@linkcode SessionSaveData}
+  version: "1.0.4",
-   */
+  migrate: (data: SessionSaveData): void => {
-  function migrateCustomPokemonDataAndNatureOverrides(data: SessionSaveData) {
     // Fix Pokemon nature overrides and custom data migration
     for (const pokemon of data.party) {
       if (pokemon["mysteryEncounterPokemonData"]) {
@@ -186,4 +202,6 @@ export const sessionMigrators = [
       }
     }
   },
-] as const;
+};
+
+export const sessionMigrators: Readonly<SessionSaveMigrator[]> = [migrateModifiers, migrateCustomPokemonData] as const;

src/system/version_migration/versions/v1_1_0.ts

@@ -1,5 +0,0 @@
-export const systemMigrators = [] as const;
-
-export const settingsMigrators = [] as const;
-
-export const sessionMigrators = [] as const;

src/system/version_migration/versions/v1_7_0.ts

@@ -1,15 +1,18 @@
+import type { SessionSaveMigrator } from "#app/@types/SessionSaveMigrator";
+import type { SystemSaveMigrator } from "#app/@types/SystemSaveMigrator";
 import { getPokemonSpecies, getPokemonSpeciesForm } from "#app/data/pokemon-species";
 import { globalScene } from "#app/global-scene";
 import { DexAttr, type SessionSaveData, type SystemSaveData } from "#app/system/game-data";
-import * as Utils from "#app/utils";
+import { isNullOrUndefined } from "#app/utils";
 
-export const systemMigrators = [
+/**
-  /**
+ * If a starter is caught, but the only forms registered as caught are not starterSelectable,
-   * If a starter is caught, but the only forms registered as caught are not starterSelectable,
+ * unlock the default form.
-   * unlock the default form.
+ * @param data - {@linkcode SystemSaveData}
-   * @param data {@linkcode SystemSaveData}
+ */
-   */
+const migrateUnselectableForms: SystemSaveMigrator = {
-  function migrateUnselectableForms(data: SystemSaveData) {
+  version: "1.7.0",
+  migrate: (data: SystemSaveData): void => {
     if (data.starterData && data.dexData) {
       Object.keys(data.starterData).forEach(sd => {
         const caughtAttr = data.dexData[sd]?.caughtAttr;
@@ -30,12 +33,13 @@ export const systemMigrators = [
       });
     }
   },
-] as const;
+};
 
-export const settingsMigrators = [] as const;
+export const systemMigrators: Readonly<SystemSaveMigrator[]> = [migrateUnselectableForms] as const;
 
-export const sessionMigrators = [
+const migrateTera: SessionSaveMigrator = {
-  function migrateTera(data: SessionSaveData) {
+  version: "1.7.0",
+  migrate: (data: SessionSaveData): void => {
     for (let i = 0; i < data.modifiers.length; ) {
       if (data.modifiers[i].className === "TerastallizeModifier") {
         data.party.forEach(p => {
@@ -63,15 +67,17 @@ export const sessionMigrators = [
     }
 
     data.party.forEach(p => {
-      if (Utils.isNullOrUndefined(p.teraType)) {
+      if (isNullOrUndefined(p.teraType)) {
         p.teraType = getPokemonSpeciesForm(p.species, p.formIndex).type1;
       }
     });
 
     data.enemyParty.forEach(p => {
-      if (Utils.isNullOrUndefined(p.teraType)) {
+      if (isNullOrUndefined(p.teraType)) {
         p.teraType = getPokemonSpeciesForm(p.species, p.formIndex).type1;
       }
     });
   },
-] as const;
+};
+
+export const sessionMigrators: Readonly<SessionSaveMigrator[]> = [migrateTera] as const;

src/system/version_migration/versions/v1_8_3.ts

@@ -1,14 +1,16 @@
+import type { SystemSaveMigrator } from "#app/@types/SystemSaveMigrator";
 import { getPokemonSpecies } from "#app/data/pokemon-species";
 import { DexAttr, type SystemSaveData } from "#app/system/game-data";
 import { Species } from "#enums/species";
 
-export const systemMigrators = [
+/**
-  /**
+ * If a starter is caught, but the only forms registered as caught are not starterSelectable,
-   * If a starter is caught, but the only forms registered as caught are not starterSelectable,
+ * unlock the default form.
-   * unlock the default form.
+ * @param data - {@linkcode SystemSaveData}
-   * @param data {@linkcode SystemSaveData}
+ */
-   */
+const migratePichuForms: SystemSaveMigrator = {
-  function migratePichuForms(data: SystemSaveData) {
+  version: "1.8.3",
+  migrate: (data: SystemSaveData): void => {
     if (data.starterData && data.dexData) {
       // This is Pichu's Pokédex number
       const sd = 172;
@@ -23,8 +25,6 @@ export const systemMigrators = [
       }
     }
   },
-] as const;
+};
 
-export const settingsMigrators = [] as const;
+export const systemMigrators: Readonly<SystemSaveMigrator[]> = [migratePichuForms] as const;
-
-export const sessionMigrators = [] as const;