fix: Add another defineItem signature when init function is passed

#1601 adjusted the typing of `defineItem` to
examine whether `defaultValue` or `fallback` were passed, and only then, remove
the `null` from the possible returned value. However, it did not accommodate
the case where an `init` function is passed to prevent a `null` return, which
was previously allowed.

Add a new type signature for this case, and add some tests for type
expectations to catch the issue.

Author: toofishes

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

@@ -1315,6 +1315,18 @@ describe('Storage Utils', () => {
         });
         expectTypeOf(item).toEqualTypeOf<WxtStorageItem<number | null, {}>>();
       });
+
+      it('should define a non-null value when options are passed with a non-null init function', () => {
+        const item = storage.defineItem(`local:test`, {
+          init: () => 123,
+        });
+        expectTypeOf(item).toEqualTypeOf<WxtStorageItem<number, {}>>();
+
+        const item2 = storage.defineItem(`local:test`, {
+          init: () => Promise.resolve(123),
+        });
+        expectTypeOf(item2).toEqualTypeOf<WxtStorageItem<number, {}>>();
+      });
     });
   });
 

packages/storage/src/index.ts

@@ -749,6 +749,12 @@ export interface WxtStorage {
     key: StorageItemKey,
     options: WxtStorageItemOptions<TValue> & { defaultValue: TValue },
   ): WxtStorageItem<TValue, TMetadata>;
+  defineItem<TValue, TMetadata extends Record<string, unknown> = {}>(
+    key: StorageItemKey,
+    options: WxtStorageItemOptions<TValue> & {
+      init: () => TValue | Promise<TValue>;
+    },
+  ): WxtStorageItem<TValue, TMetadata>;
   defineItem<TValue, TMetadata extends Record<string, unknown> = {}>(
     key: StorageItemKey,
     options: WxtStorageItemOptions<TValue>,