fix(store): 🐞 improve state type

✅ Closes: #510
ngneat · Feb 3, 2024 · ee784a4 · ee784a4
1 parent 7dd238c
commit ee784a4
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Showing 3 changed files with 26 additions and 20 deletions.
diff --git a/packages/store/src/lib/create-store.ts b/packages/store/src/lib/create-store.ts
@@ -1,17 +1,8 @@
-import { createState, PropsFactory } from './state';
+import { createState, Merge, PropsFactory } from './state';
 import { Store } from './store';
 
-type UnionToIntersection<U> = (U extends any ? (k: U) => void : never) extends (
-  k: infer I
-) => void
-  ? I
-  : never;
-type Merge<State extends any[], Key extends PropertyKey> = UnionToIntersection<
-  State[number][Key]
->;
-
 export function createStore<
-  S extends [PropsFactory<any, any>, ...PropsFactory<any, any>[]]
+  S extends [PropsFactory<any, any>, ...PropsFactory<any, any>[]],
 >(
   storeConfig: StoreConfig,
   ...propsFactories: S

diff --git a/packages/store/src/lib/state.ts b/packages/store/src/lib/state.ts
@@ -1,11 +1,9 @@
-type UnionToIntersection<U> = (U extends any ? (k: U) => void : never) extends (
-  k: infer I
-) => void
-  ? I
-  : never;
-type Merge<State extends any[], Key extends PropertyKey> = UnionToIntersection<
-  State[number][Key]
->;
+export type Merge<
+  State extends Record<Key, any>[],
+  Key extends PropertyKey,
+> = State extends [Record<Key, infer V>, ...infer Rest extends any[]]
+  ? V & Merge<Rest, Key>
+  : unknown;
 
 export type PropsFactory<Props, Config> = { props: Props; config: Config };
 export type EmptyConfig = undefined;

diff --git a/packages/store/src/lib/types.spec.ts b/packages/store/src/lib/types.spec.ts
@@ -31,7 +31,7 @@ describe('Store types', () => {
   it('should set the correct types', () => {
     const { state, config } = createState(
       withProps<Props>({ id: 1, name: 'foo' }),
-      withFoo()
+      withFoo(),
     );
 
     expectTypeOf(state).toEqualTypeOf<Props & FooProps>();
@@ -67,4 +67,21 @@ describe('Store types', () => {
       //
     }
   });
+
+  it('should work with union types', () => {
+    type Circle = { kind: 'CIRCLE'; diameter: number };
+    type Square = { kind: 'SQUARE'; edge: number };
+    type Shape = Circle | Square;
+
+    const v1 = createState(
+      withProps<Shape>({ kind: 'CIRCLE', diameter: 2 }),
+      withProps<{ id: number }>({ id: 1 }),
+    );
+
+    expectTypeOf(v1.state).toEqualTypeOf<Shape & { id: number }>();
+
+    const v2 = createState(withProps<Shape>({ kind: 'CIRCLE', diameter: 2 }));
+
+    expectTypeOf(v2.state).toEqualTypeOf<Shape>();
+  });
 });