feat(store) introduce opt-in strict projectors from createSelector

Author: david-shortman

modules/router-store/spec/types/selectors.spec.ts

@@ -105,15 +105,22 @@ describe('router selectors', () => {
     );
   });
 
-  it('selectUrl should return string', () => {
+  it('selectUrl with strict option should return strict selector with [string] slices and string projection', () => {
     expectSnippet(`
       export const selector = createSelector(
+        selectUrl,
+        url => url,
+        { strict: true }
+      );
+    `).toInfer('selector', 'StrictMemoizedSelector<[string], string, State>');
+  });
+
+  it('selectUrl with strict generic params should return strict selector with [string] slices and string projection', () => {
+    expectSnippet(`
+      export const selector = createSelector<[string], string>(
         selectUrl,
         url => url
       );
-    `).toInfer(
-      'selector',
-      'MemoizedSelector<State, string, DefaultProjectorFn<string>>'
-    );
+    `).toInfer('selector', 'StrictMemoizedSelector<[string], string, unknown>');
   });
 });

modules/store/src/selector.ts

@@ -17,13 +17,21 @@ export type ComparatorFn = (a: any, b: any) => boolean;
 
 export type DefaultProjectorFn<T> = (...args: any[]) => T;
 
+export type ProjectorFn<Args extends unknown[], T> = (...args: Args) => T;
+
+export type StrictMemoizedSelector<
+  Slices extends unknown[],
+  Result,
+  State = unknown
+> = MemoizedSelector<State, Result, (...slices: Slices) => Result>;
+
 export interface MemoizedSelector<
   State,
   Result,
-  ProjectorFn = DefaultProjectorFn<Result>
+  Projector = DefaultProjectorFn<Result>
 > extends Selector<State, Result> {
   release(): void;
-  projector: ProjectorFn;
+  projector: Projector;
   setResult: (result?: Result) => void;
   clearResult: () => void;
 }
@@ -122,6 +130,22 @@ export function defaultMemoize(
   return { memoized, reset, setResult, clearResult };
 }
 
+export function createSelector<
+  State,
+  Slices extends unknown[],
+  Result,
+  IsStrict extends boolean
+>(
+  ...args: [...Selector<State, unknown>[], unknown, unknown] &
+    [
+      ...{ [i in keyof Slices]: Selector<State, Slices[i]> },
+      (...s: Slices) => Result,
+      { strict: IsStrict }
+    ]
+): IsStrict extends true
+  ? StrictMemoizedSelector<Slices, Result, State>
+  : MemoizedSelector<State, Result>;
+
 export function createSelector<State, Slices extends unknown[], Result>(
   ...args: [...Selector<State, unknown>[], unknown] &
     [
@@ -272,6 +296,20 @@ export function createSelector<
   ) => Result
 ): MemoizedSelectorWithProps<State, Props, Result>;
 
+export function createSelector<
+  State,
+  Slices extends unknown[],
+  Result,
+  IsStrict extends boolean
+>(
+  selectors: Selector<State, unknown>[] &
+    [...{ [i in keyof Slices]: Selector<State, Slices[i]> }],
+  projector: (...s: Slices) => Result,
+  options: { strict: IsStrict }
+): IsStrict extends true
+  ? StrictMemoizedSelector<Slices, Result, State>
+  : MemoizedSelector<State, Result>;
+
 export function createSelector<State, Slices extends unknown[], Result>(
   selectors: Selector<State, unknown>[] &
     [...{ [i in keyof Slices]: Selector<State, Slices[i]> }],