fix: fix typescript error on defineItem fallback (#1601)

packages/storage/src/__tests__/index.test.ts

@@ -1281,6 +1281,19 @@ describe('Storage Utils', () => {
       it('should define a nullable value when options are not passed', () => {
         const item = storage.defineItem<number>(`local:test`);
         expectTypeOf(item).toEqualTypeOf<WxtStorageItem<number | null, {}>>();
+
+        const item2 = storage.defineItem<number>(`local:test`, {});
+        expectTypeOf(item2).toEqualTypeOf<WxtStorageItem<number | null, {}>>();
+
+        const item3 = storage.defineItem<number>(`local:test`, {
+          fallback: undefined,
+        });
+        expectTypeOf(item3).toEqualTypeOf<WxtStorageItem<number | null, {}>>();
+
+        const item4 = storage.defineItem<number>(`local:test`, {
+          defaultValue: undefined,
+        });
+        expectTypeOf(item4).toEqualTypeOf<WxtStorageItem<number | null, {}>>();
       });
 
       it('should define a non-null value when options are passed with a nullish default value', () => {
@@ -1288,6 +1301,11 @@ describe('Storage Utils', () => {
           defaultValue: 123,
         });
         expectTypeOf(item).toEqualTypeOf<WxtStorageItem<number, {}>>();
+
+        const item2 = storage.defineItem(`local:test`, {
+          fallback: 123,
+        });
+        expectTypeOf(item2).toEqualTypeOf<WxtStorageItem<number, {}>>();
       });
 
       it('should define a nullable value when options are passed with null default value', () => {

packages/storage/src/index.ts

@@ -750,8 +750,16 @@ export interface WxtStorage {
   ): WxtStorageItem<TValue | null, TMetadata>;
   defineItem<TValue, TMetadata extends Record<string, unknown> = {}>(
     key: StorageItemKey,
-    options: WxtStorageItemOptions<TValue>,
+    options: WxtStorageItemOptions<TValue> & { fallback: TValue },
   ): WxtStorageItem<TValue, TMetadata>;
+  defineItem<TValue, TMetadata extends Record<string, unknown> = {}>(
+    key: StorageItemKey,
+    options: WxtStorageItemOptions<TValue> & { defaultValue: TValue },
+  ): WxtStorageItem<TValue, TMetadata>;
+  defineItem<TValue, TMetadata extends Record<string, unknown> = {}>(
+    key: StorageItemKey,
+    options: WxtStorageItemOptions<TValue>,
+  ): WxtStorageItem<TValue | null, TMetadata>;
 }
 
 interface WxtStorageDriver {