chore: Better type resolving

Author: imp-dance

README.md

@@ -202,20 +202,36 @@ type LoaderData = InferLoaderData<typeof useLoader>;
 
 Typescript should infer the loader data type automatically inside `withLoader`, but if you need the type elsewhere then this could be useful.
 
-## Future features & wants
+# Extending loaders
 
-- Better type resolving:
+You can extend a loader like such:
+
+```tsx
+const baseLoader = createLoader({
+  onLoading: () => <Loading />,
+});
+
+const pokemonLoader = baseLoader.extend({
+  queries: (name: string) => [useGetPokemon(name)],
+  queriesArg: (props: PokemonProps) => props.name.toLowerCase(),
+});
+```
+
+New properties will overwrite existing.
+
+> If the loader you extend has a `transform` function, and you are changing the `queries` function, you might need to do this to resolve the types properly:
 
 ```typescript
-createLoader({
-  queries: () => {
-    return [useGetUser(), useGetPosts()] as const;
-  },
-  transform: function (queries) {
-    // queries here are guaranteed to have .data, but currently the type resolves data as optional.
-    return {
-      name: queries[0].data.name, // is technically safe, but typescript might complain
-    };
-  },
+const baseLoader = createLoader({
+  queries: () => [...],
+  transform: () => {i_want: "this-format"},
+})
+
+const pokemonLoader = baseLoader.extend({
+  queries: () => [...],
+  transform: (q) => q, // Reapply default transform for query
 });
+
+type Test = ReturnType<typeof pokemonLoader.useLoader>;
+// { i_want: string; }
 ```

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@ryfylke-react/rtk-query-loader",
-  "version": "0.2.6",
+  "version": "0.2.7",
   "description": "Lets you create loaders that contain multiple RTK queries.",
   "main": "./dist/cjs/index.js",
   "module": "./dist/esm/index.js",

src/createLoader.ts

@@ -3,7 +3,7 @@ import * as Types from "./types";
 
 export const createUseLoader = <
   QRU extends readonly Types.UseQueryResult<unknown>[],
-  R extends unknown = QRU,
+  R extends unknown = Types.MakeDataRequired<QRU>,
   A = never
 >(
   createUseLoaderArgs: Types.CreateUseLoaderArgs<QRU, R, A>
@@ -15,7 +15,9 @@ export const createUseLoader = <
 
     if (aggregatedQuery.isSuccess) {
       const data = createUseLoaderArgs.transform
-        ? createUseLoaderArgs.transform(createdQueries)
+        ? createUseLoaderArgs.transform(
+            createdQueries as unknown as Types.MakeDataRequired<QRU>
+          )
         : createdQueries;
 
       return {
@@ -32,7 +34,7 @@ export const createUseLoader = <
 export const createLoader = <
   P extends unknown,
   QRU extends readonly Types.UseQueryResult<unknown>[],
-  R extends unknown = QRU,
+  R extends unknown = Types.MakeDataRequired<QRU>,
   A = never
 >(
   createLoaderArgs: Types.CreateLoaderArgs<P, QRU, R, A>

src/types.ts

@@ -23,10 +23,14 @@ export type UseQueryResult<T> = {
   refetch: () => void; // A function to force refetch the query
 };
 
+export type MakeDataRequired<T> = {
+  [K in keyof T]-?: Required<T[K]>;
+};
+
 export type LoaderTransformFunction<
   QRU extends readonly UseQueryResult<unknown>[],
   R extends unknown
-> = (queries: QRU) => R;
+> = (queries: MakeDataRequired<QRU>) => R;
 
 export type OptionalGenericArg<T> = T extends never ? [] : [T];
 
@@ -45,7 +49,7 @@ export type UseLoader<A, R> = (
 
 export type CreateLoaderType = <
   QRU extends readonly UseQueryResult<unknown>[],
-  R extends unknown = QRU,
+  R extends unknown = MakeDataRequired<QRU>,
   A = never
 >(
   createLoaderArgs: CreateUseLoaderArgs<QRU, R, A>
@@ -77,7 +81,7 @@ export type WithLoaderArgs<
 export type CreateLoaderArgs<
   P extends unknown,
   QRU extends readonly UseQueryResult<unknown>[],
-  R extends unknown = QRU,
+  R extends unknown = MakeDataRequired<QRU>,
   A = never
 > = Partial<CreateUseLoaderArgs<QRU, R, A>> & {
   queriesArg?: (props: P) => A;
@@ -108,7 +112,9 @@ export type Loader<
   extend: <
     QRUb extends readonly UseQueryResult<unknown>[],
     Pb extends unknown = P,
-    Rb extends unknown = QRUb extends unknown ? R : QRUb,
+    Rb extends unknown = QRUb extends unknown
+      ? R
+      : MakeDataRequired<QRUb>,
     Ab = A
   >(
     newLoader: Partial<CreateLoaderArgs<Pb, QRUb, Rb, Ab>>