Improved HookHandler type

framework/bigcommerce/cart/use-cart.tsx

@@ -1,4 +1,4 @@
 import useCommerceCart, { UseCart } from '@commerce/cart/use-cart'
-import { BigcommerceProvider } from '..'
+import type { BigcommerceProvider } from '..'
 
 export default useCommerceCart as UseCart<BigcommerceProvider>

framework/bigcommerce/index.tsx

@@ -49,7 +49,13 @@ const fetcher: Fetcher<any> = async ({
   throw await getError(res)
 }
 
-const useCart: HookHandler<Cart, CartInput, any, any, { isEmpty?: boolean }> = {
+const useCart: HookHandler<
+  Cart | null,
+  CartInput,
+  any,
+  any,
+  { isEmpty?: boolean }
+> = {
   fetchOptions: {
     url: '/api/bigcommerce/cart',
     method: 'GET',

framework/commerce/index.tsx

@@ -16,29 +16,19 @@ const Commerce = createContext<CommerceContextValue<any> | {}>({})
 
 export type Provider = CommerceConfig & {
   cart?: {
-    useCart?: HookHandler<Cart, CartInput>
+    useCart?: HookHandler<Cart | null, CartInput>
   }
   cartNormalizer(data: any): Cart
 }
 
 export type HookHandler<Data, Input, Result = any, Body = any, State = {}> = {
-  swrOptions?: SwrOptions<Data | null, Input, Result>
-  onResponse?(
-    response: ResponseState<Data | null>
-  ): ResponseState<Data | null> & State
+  swrOptions?: SwrOptions<Data, Input, Result>
+  onResponse?(response: ResponseState<Data>): ResponseState<Data> & State
   onMutation?: any
   fetchOptions?: HookFetcherOptions
-} & (
-  | // TODO: Maybe the normalizer is not required if it's used by the API route directly?
-  {
-      fetcher: HookFetcherFn<Data | null, Input, Result, Body>
-      normalizer?(data: Result): Data
-    }
-  | {
-      fetcher?: never
-      normalizer(data: Result): Data
-    }
-)
+  fetcher?: HookFetcherFn<Data, Input, Result, Body>
+  normalizer?(data: Result): Data
+}
 
 export type CommerceProps<P extends Provider> = {
   children?: ReactNode