feat(state): add default transform function to select

AdrianRomanski · web-flow · commit 7875319ff84a · 2024-04-14T17:46:52.000+02:00
* feat: default transform function for select
diff --git a/libs/state/selections/src/lib/operators/select.ts b/libs/state/selections/src/lib/operators/select.ts
@@ -99,7 +99,7 @@ export function select<T, A, B, C, D, E>(
  */
 export function select<T extends object, K extends keyof T, R>(
   keys: K[],
-  fn: (slice: PickSlice<T, K>) => R,
+  fn?: (slice: PickSlice<T, K>) => R,
   keyCompareMap?: KeyCompareMap<Pick<T, K>>
 ): OperatorFunction<T, R>;
 
@@ -209,7 +209,7 @@ export function select<T extends Record<string, unknown>>(
     | [k: string, fn: (val: unknown) => unknown]
     | [
         keys: string[],
-        fn: (slice: unknown) => unknown,
+        fn?: (slice: unknown) => unknown,
         keyCompareMap?: KeyCompareMap<T>
       ]
 ): OperatorFunction<T, unknown> {
@@ -219,13 +219,16 @@ export function select<T extends Record<string, unknown>>(
     } else if (isStringAndFunctionTupleGuard(opOrMapFn)) {
       return state$.pipe(stateful(map((s) => opOrMapFn[1](s[opOrMapFn[0]]))));
     } else if (isStringArrayFunctionAndOptionalObjectTupleGuard(opOrMapFn)) {
-      return state$.pipe(
-        selectSlice<T & object, keyof T>(
-          opOrMapFn[0] as (keyof T)[],
-          opOrMapFn[2]
-        ),
-        stateful(map(opOrMapFn[1]))
-      );
+      const selectedState$: Observable<PickSlice<T & object, keyof T>> =
+        state$.pipe(
+          selectSlice<T & object, keyof T>(
+            opOrMapFn[0] as (keyof T)[],
+            opOrMapFn[2] as KeyCompareMap<{ [P in keyof T]: (T & object)[P] }>
+          )
+        );
+      return typeof opOrMapFn[1] === 'undefined'
+        ? selectedState$
+        : selectedState$.pipe(stateful(map(opOrMapFn[1])));
     } else if (isStringArrayGuard(opOrMapFn)) {
       return state$.pipe(
         stateful(
diff --git a/libs/state/selections/src/lib/utils/guards.ts b/libs/state/selections/src/lib/utils/guards.ts
@@ -65,7 +65,7 @@ export function isStringArrayFunctionAndOptionalObjectTupleGuard<R>(
 ): op is [strs: string[], fn: (val: any) => R, obj?: object] {
   return (
     isStringArrayGuard(op[0] as any) &&
-    typeof op[1] === 'function' &&
+    (typeof op[1] === 'function' || typeof op[1] === 'undefined') &&
     (op[2] === undefined || typeof op[2] === 'object')
   );
 }
diff --git a/libs/state/spec/rx-state.service.spec.ts b/libs/state/spec/rx-state.service.spec.ts
@@ -262,6 +262,18 @@ describe('RxStateService', () => {
         });
       });
 
+      it('should return mapped slice with default function if no one provided', () => {
+        testScheduler.run(({ expectObservable }) => {
+          const state = setupState({ initialState: initialPrimitiveState });
+          expectObservable(state.select(['num', 'str'])).toBe('s', {
+            s: {
+              num: 42,
+              str: 'str',
+            },
+          });
+        });
+      });
+
       it('should return mapped slice on select with keys, function and key compare map', () => {
         testScheduler.run(({ expectObservable }) => {
           const state = setupState({
diff --git a/libs/state/src/lib/rx-state.service.ts b/libs/state/src/lib/rx-state.service.ts
@@ -694,7 +694,7 @@ export class RxState<State extends object>
    */
   select<Key extends keyof State, Value>(
     keys: Key[],
-    fn: (slice: PickSlice<State, Key>) => Value,
+    fn?: (slice: PickSlice<State, Key>) => Value,
     keyCompareMap?: KeyCompareMap<Pick<State, Key>>
   ): Observable<Value>;
 
@@ -813,7 +813,7 @@ export class RxState<State extends object>
       | [k: string, fn: (val: unknown) => unknown]
       | [
           keys: string[],
-          fn: (slice: unknown) => unknown,
+          fn?: (slice: unknown) => unknown,
           keyCompareMap?: KeyCompareMap<State>
         ]
   ): Observable<State | Return> {

Original file line number	Diff line number	Diff line change
`@@ -65,7 +65,7 @@ export function isStringArrayFunctionAndOptionalObjectTupleGuard<R>(`
`65`	`65`	`): op is [strs: string[], fn: (val: any) => R, obj?: object] {`
`66`	`66`	`return (`
`67`	`67`	`isStringArrayGuard(op[0] as any) &&`
`68`		`- typeof op[1] === 'function' &&`
	`68`	`+ (typeof op[1] === 'function' \|\| typeof op[1] === 'undefined') &&`
`69`	`69`	`(op[2] === undefined \|\| typeof op[2] === 'object')`
`70`	`70`	`);`
`71`	`71`	`}`