chore(store): add initial version of new strongly typed createSelector (

#1823)

packages/store/src/selectors/create-selector.util.ts

@@ -0,0 +1,156 @@
+import { createSelector as createSelectorOrig } from '../utils/selector-utils';
+import { SelectorDef, SelectorReturnType } from './selector-types.util';
+
+type SelectorArg = SelectorDef<any>;
+
+type CreationMetadata = Parameters<typeof createSelectorOrig>[2];
+
+// NOTE: This is temporarily named differently to `createSelector`, and
+//  will be renamed when the types interface is finalised and publically exported.
+//  Adding this here so that other dependent types can leverage this in the interim.
+export function createSelectorX<
+  S1 extends SelectorArg,
+  TProjector extends (s1: SelectorReturnType<S1>) => any
+>(
+  selectors: [S1],
+  projector: TProjector,
+  creationMetadata?: Partial<CreationMetadata>
+): TProjector;
+
+export function createSelectorX<
+  S1 extends SelectorArg,
+  S2 extends SelectorArg,
+  TProjector extends (s1: SelectorReturnType<S1>, s2: SelectorReturnType<S2>) => any
+>(
+  selectors: [S1, S2],
+  projector: TProjector,
+  creationMetadata?: Partial<CreationMetadata>
+): TProjector;
+
+export function createSelectorX<
+  S1 extends SelectorArg,
+  S2 extends SelectorArg,
+  S3 extends SelectorArg,
+  TProjector extends (
+    s1: SelectorReturnType<S1>,
+    s2: SelectorReturnType<S2>,
+    s3: SelectorReturnType<S3>
+  ) => any
+>(
+  selectors: [S1, S2, S3],
+  projector: TProjector,
+  creationMetadata?: Partial<CreationMetadata>
+): TProjector;
+
+export function createSelectorX<
+  S1 extends SelectorArg,
+  S2 extends SelectorArg,
+  S3 extends SelectorArg,
+  S4 extends SelectorArg,
+  TProjector extends (
+    s1: SelectorReturnType<S1>,
+    s2: SelectorReturnType<S2>,
+    s3: SelectorReturnType<S3>,
+    s4: SelectorReturnType<S4>
+  ) => any
+>(
+  selectors: [S1, S2, S3, S4],
+  projector: TProjector,
+  creationMetadata?: Partial<CreationMetadata>
+): TProjector;
+
+export function createSelectorX<
+  S1 extends SelectorArg,
+  S2 extends SelectorArg,
+  S3 extends SelectorArg,
+  S4 extends SelectorArg,
+  S5 extends SelectorArg,
+  TProjector extends (
+    s1: SelectorReturnType<S1>,
+    s2: SelectorReturnType<S2>,
+    s3: SelectorReturnType<S3>,
+    s4: SelectorReturnType<S4>,
+    s5: SelectorReturnType<S5>
+  ) => any
+>(
+  selectors: [S1, S2, S3, S4, S5],
+  projector: TProjector,
+  creationMetadata?: Partial<CreationMetadata>
+): TProjector;
+
+export function createSelectorX<
+  S1 extends SelectorArg,
+  S2 extends SelectorArg,
+  S3 extends SelectorArg,
+  S4 extends SelectorArg,
+  S5 extends SelectorArg,
+  S6 extends SelectorArg,
+  TProjector extends (
+    s1: SelectorReturnType<S1>,
+    s2: SelectorReturnType<S2>,
+    s3: SelectorReturnType<S3>,
+    s4: SelectorReturnType<S4>,
+    s5: SelectorReturnType<S5>,
+    s6: SelectorReturnType<S6>
+  ) => any
+>(
+  selectors: [S1, S2, S3, S4, S5, S6],
+  projector: TProjector,
+  creationMetadata?: Partial<CreationMetadata>
+): TProjector;
+
+export function createSelectorX<
+  S1 extends SelectorArg,
+  S2 extends SelectorArg,
+  S3 extends SelectorArg,
+  S4 extends SelectorArg,
+  S5 extends SelectorArg,
+  S6 extends SelectorArg,
+  S7 extends SelectorArg,
+  TProjector extends (
+    s1: SelectorReturnType<S1>,
+    s2: SelectorReturnType<S2>,
+    s3: SelectorReturnType<S3>,
+    s4: SelectorReturnType<S4>,
+    s5: SelectorReturnType<S5>,
+    s6: SelectorReturnType<S6>,
+    s7: SelectorReturnType<S7>
+  ) => any
+>(
+  selectors: [S1, S2, S3, S4, S5, S6, S7],
+  projector: TProjector,
+  creationMetadata?: Partial<CreationMetadata>
+): TProjector;
+
+export function createSelectorX<
+  S1 extends SelectorArg,
+  S2 extends SelectorArg,
+  S3 extends SelectorArg,
+  S4 extends SelectorArg,
+  S5 extends SelectorArg,
+  S6 extends SelectorArg,
+  S7 extends SelectorArg,
+  S8 extends SelectorArg,
+  TProjector extends (
+    s1: SelectorReturnType<S1>,
+    s2: SelectorReturnType<S2>,
+    s3: SelectorReturnType<S3>,
+    s4: SelectorReturnType<S4>,
+    s5: SelectorReturnType<S5>,
+    s6: SelectorReturnType<S6>,
+    s7: SelectorReturnType<S7>,
+    s8: SelectorReturnType<S8>
+  ) => any
+>(
+  selectors: [S1, S2, S3, S4, S5, S6, S7, S8],
+  projector: TProjector,
+  creationMetadata?: Partial<CreationMetadata>
+): TProjector;
+
+export function createSelectorX<T extends (...args: any[]) => any>(
+  selectors: any[],
+  projector: T,
+  creationMetadata?: Partial<CreationMetadata>
+): T {
+  return createSelectorOrig<T>(selectors, projector, <CreationMetadata>creationMetadata);
+}

packages/store/src/selectors/selector-types.util.ts

@@ -0,0 +1,28 @@
+import { StateToken } from '@ngxs/store';
+import { StateClass } from '@ngxs/store/internals';
+
+export type SelectorFunc<TModel> = (...arg: any[]) => TModel;
+
+export type TypedSelector<TModel> = StateToken<TModel> | SelectorFunc<TModel>;
+
+export type StateSelector = StateClass<any>;
+
+export type SelectorDef<TModel> = StateSelector | TypedSelector<TModel>;
+
+export type SelectorReturnType<T extends SelectorDef<any>> = T extends StateToken<infer R1>
+  ? R1
+  : T extends SelectorFunc<infer R2>
+  ? R2
+  : T extends StateClass<any>
+  ? any /* (Block comment to stop prettier breaking the comment below)
+  // If the state selector is a class then we should infer its return type to `any`, and not to `unknown`.
+  // Since we'll get an error that `Type 'unknown' is not assignable to type 'AuthStateModel'.`
+  // The `unknown` type is not overridable when the strict mode is enabled:
+  // function doSomethingWithArray(array: number[], factory: (x: unknown) => void) {
+  //   array.forEach(factory);
+  // }
+  // doSomethingWithArray([1, 2], (x: number) => console.log(x));
+  //                              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+  //                              Type 'unknown' is not assignable to type 'number'.
+  */
+  : never;