Introduce pre-typed createSelector via createSelector.withTypes<RootState>() method

docs/examples/createSelector/annotateResultFunction.ts

@@ -0,0 +1,28 @@
+import { createSelector } from 'reselect'
+
+interface Todo {
+  id: number
+  completed: boolean
+}
+
+interface Alert {
+  id: number
+  read: boolean
+}
+
+export interface RootState {
+  todos: Todo[]
+  alerts: Alert[]
+}
+
+export const createAppSelector = createSelector.withTypes<RootState>()
+
+const selectTodoIds = createAppSelector(
+  // Type of `state` is set to `RootState`, no need to manually set the type
+  state => state.todos,
+  // ❌ Known limitation: Parameter types are not inferred in this scenario
+  // so you will have to manually annotate them.
+  // highlight-start
+  (todos: Todo[]) => todos.map(({ id }) => id)
+  // highlight-end
+)

docs/examples/createSelector/createAppSelector.ts

@@ -0,0 +1,36 @@
+import microMemoize from 'micro-memoize'
+import { shallowEqual } from 'react-redux'
+import { createSelectorCreator, lruMemoize } from 'reselect'
+
+export interface RootState {
+  todos: { id: number; completed: boolean }[]
+  alerts: { id: number; read: boolean }[]
+}
+
+export const createAppSelector = createSelectorCreator({
+  memoize: lruMemoize,
+  argsMemoize: microMemoize,
+  memoizeOptions: {
+    maxSize: 10,
+    equalityCheck: shallowEqual,
+    resultEqualityCheck: shallowEqual
+  },
+  argsMemoizeOptions: {
+    isEqual: shallowEqual,
+    maxSize: 10
+  },
+  devModeChecks: {
+    identityFunctionCheck: 'never',
+    inputStabilityCheck: 'always'
+  }
+}).withTypes<RootState>()
+
+const selectReadAlerts = createAppSelector(
+  [
+    // Type of `state` is set to `RootState`, no need to manually set the type
+    // highlight-start
+    state => state.alerts
+    // highlight-end
+  ],
+  alerts => alerts.filter(({ read }) => read)
+)

docs/examples/createSelector/withTypes.ts

@@ -0,0 +1,18 @@
+import { createSelector } from 'reselect'
+
+export interface RootState {
+  todos: { id: number; completed: boolean }[]
+  alerts: { id: number; read: boolean }[]
+}
+
+export const createAppSelector = createSelector.withTypes<RootState>()
+
+const selectTodoIds = createAppSelector(
+  [
+    // Type of `state` is set to `RootState`, no need to manually set the type
+    // highlight-start
+    state => state.todos
+    // highlight-end
+  ],
+  todos => todos.map(({ id }) => id)
+)

src/createSelectorCreator.ts

@@ -29,12 +29,14 @@ import {
  *
  * @template MemoizeFunction - The type of the memoize function that is used to memoize the `resultFunc` inside `createSelector` (e.g., `lruMemoize` or `weakMapMemoize`).
  * @template ArgsMemoizeFunction - The type of the optional memoize function that is used to memoize the arguments passed into the output selector generated by `createSelector` (e.g., `lruMemoize` or `weakMapMemoize`). If none is explicitly provided, `weakMapMemoize` will be used.
+ * @template StateType - The type of state that the selectors created with this selector creator will operate on.
  *
  * @public
  */
 export interface CreateSelectorFunction<
   MemoizeFunction extends UnknownMemoizer = typeof weakMapMemoize,
-  ArgsMemoizeFunction extends UnknownMemoizer = typeof weakMapMemoize
+  ArgsMemoizeFunction extends UnknownMemoizer = typeof weakMapMemoize,
+  StateType = any
 > {
   /**
    * Creates a memoized selector function.
@@ -47,9 +49,9 @@ export interface CreateSelectorFunction<
    * @template OverrideMemoizeFunction - The type of the optional `memoize` function that could be passed into the options object to override the original `memoize` function that was initially passed into `createSelectorCreator`.
    * @template OverrideArgsMemoizeFunction - The type of the optional `argsMemoize` function that could be passed into the options object to override the original `argsMemoize` function that was initially passed into `createSelectorCreator`.
    *
-   * @see {@link https://github.com/reduxjs/reselect#createselectorinputselectors--inputselectors-resultfunc-createselectoroptions createSelector}
+   * @see {@link https://reselect.js.org/api/createselector `createSelector`}
    */
-  <InputSelectors extends SelectorArray, Result>(
+  <InputSelectors extends SelectorArray<StateType>, Result>(
     ...createSelectorArgs: [
       ...inputSelectors: InputSelectors,
       combiner: Combiner<InputSelectors, Result>
@@ -73,10 +75,10 @@ export interface CreateSelectorFunction<
    * @template OverrideMemoizeFunction - The type of the optional `memoize` function that could be passed into the options object to override the original `memoize` function that was initially passed into `createSelectorCreator`.
    * @template OverrideArgsMemoizeFunction - The type of the optional `argsMemoize` function that could be passed into the options object to override the original `argsMemoize` function that was initially passed into `createSelectorCreator`.
    *
-   * @see {@link https://github.com/reduxjs/reselect#createselectorinputselectors--inputselectors-resultfunc-createselectoroptions createSelector}
+   * @see {@link https://reselect.js.org/api/createselector `createSelector`}
    */
   <
-    InputSelectors extends SelectorArray,
+    InputSelectors extends SelectorArray<StateType>,
     Result,
     OverrideMemoizeFunction extends UnknownMemoizer = MemoizeFunction,
     OverrideArgsMemoizeFunction extends UnknownMemoizer = ArgsMemoizeFunction
@@ -114,10 +116,10 @@ export interface CreateSelectorFunction<
    * @template OverrideMemoizeFunction - The type of the optional `memoize` function that could be passed into the options object to override the original `memoize` function that was initially passed into `createSelectorCreator`.
    * @template OverrideArgsMemoizeFunction - The type of the optional `argsMemoize` function that could be passed into the options object to override the original `argsMemoize` function that was initially passed into `createSelectorCreator`.
    *
-   * @see {@link https://github.com/reduxjs/reselect#createselectorinputselectors--inputselectors-resultfunc-createselectoroptions createSelector}
+   * @see {@link https://reselect.js.org/api/createselector `createSelector`}
    */
   <
-    InputSelectors extends SelectorArray,
+    InputSelectors extends SelectorArray<StateType>,
     Result,
     OverrideMemoizeFunction extends UnknownMemoizer = MemoizeFunction,
     OverrideArgsMemoizeFunction extends UnknownMemoizer = ArgsMemoizeFunction
@@ -139,6 +141,46 @@ export interface CreateSelectorFunction<
     OverrideArgsMemoizeFunction
   > &
     InterruptRecursion
+
+  /**
+   * Creates a "pre-typed" version of {@linkcode createSelector createSelector}
+   * where the `state` type is predefined.
+   *
+   * This allows you to set the `state` type once, eliminating the need to
+   * specify it with every {@linkcode createSelector createSelector} call.
+   *
+   * @returns A pre-typed `createSelector` with the state type already defined.
+   *
+   * @example
+   * ```ts
+   * import { createSelector } from 'reselect'
+   *
+   * export interface RootState {
+   *   todos: { id: number; completed: boolean }[]
+   *   alerts: { id: number; read: boolean }[]
+   * }
+   *
+   * export const createAppSelector = createSelector.withTypes<RootState>()
+   *
+   * const selectTodoIds = createAppSelector(
+   *   [
+   *     // Type of `state` is set to `RootState`, no need to manually set the type
+   *     state => state.todos
+   *   ],
+   *   todos => todos.map(({ id }) => id)
+   * )
+   * ```
+   * @template OverrideStateType - The specific type of state used by all selectors created with this selector creator.
+   *
+   * @see {@link https://reselect.js.org/api/createselector#defining-a-pre-typed-createselector `createSelector.withTypes`}
+   *
+   * @since 5.0.2
+   */
+  withTypes<OverrideStateType extends StateType>(): CreateSelectorFunction<
+    MemoizeFunction,
+    ArgsMemoizeFunction,
+    OverrideStateType
+  >
 }
 
 /**
@@ -226,7 +268,8 @@ export function createSelectorCreator<MemoizeFunction extends UnknownMemoizer>(
 ): CreateSelectorFunction<MemoizeFunction>
 
 /**
- * Creates a selector creator function with the specified memoization function and options for customizing memoization behavior.
+ * Creates a selector creator function with the specified memoization
+ * function and options for customizing memoization behavior.
  *
  * @param memoizeOrOptions - Either A `memoize` function or an `options` object containing the `memoize` function.
  * @param memoizeOptionsFromArgs - Optional configuration options for the memoization function. These options are then passed to the memoize function as the second argument onwards.
@@ -426,6 +469,11 @@ export function createSelectorCreator<
       OverrideArgsMemoizeFunction
     >
   }
+
+  Object.assign(createSelector, {
+    withTypes: () => createSelector
+  })
+
   return createSelector as CreateSelectorFunction<
     MemoizeFunction,
     ArgsMemoizeFunction

src/types.ts

@@ -41,7 +41,7 @@ export type Selector<
  *
  * @public
  */
-export type SelectorArray = readonly Selector[]
+export type SelectorArray<State = any> = readonly Selector<State>[]
 
 /**
  * Extracts an array of all return types from all input selectors.

test/createSelector.withTypes.test.ts

@@ -0,0 +1,23 @@
+import { createSelector } from 'reselect'
+import type { RootState } from './testUtils'
+import { localTest } from './testUtils'
+
+describe(createSelector.withTypes, () => {
+  const createTypedSelector = createSelector.withTypes<RootState>()
+
+  localTest('should return createSelector', ({ state }) => {
+    expect(createTypedSelector.withTypes).to.be.a('function')
+
+    expect(createTypedSelector.withTypes().withTypes).to.be.a('function')
+
+    expect(createTypedSelector).toBe(createSelector)
+
+    const selectTodoIds = createTypedSelector([state => state.todos], todos =>
+      todos.map(({ id }) => id)
+    )
+
+    expect(selectTodoIds).toBeMemoizedSelector()
+
+    expect(selectTodoIds(state)).to.be.an('array').that.is.not.empty
+  })
+})

test/customMatchers.d.ts

@@ -0,0 +1,10 @@
+import type { Assertion, AsymmetricMatchersContaining } from 'vitest'
+
+interface CustomMatchers<R = unknown> {
+  toBeMemoizedSelector(): R
+}
+
+declare module 'vitest' {
+  interface Assertion<T = any> extends CustomMatchers<T> {}
+  interface AsymmetricMatchersContaining extends CustomMatchers {}
+}

test/reselect.spec.ts

@@ -15,6 +15,7 @@ import type { RootState } from './testUtils'
 import {
   addTodo,
   deepClone,
+  isMemoizedSelector,
   localTest,
   setEnvToProd,
   toggleCompleted
@@ -479,43 +480,9 @@ describe('argsMemoize and memoize', () => {
     const hasUndefinedValues = (object: object) => {
       return Object.values(object).some(e => e == null)
     }
-    const isMemoizedSelector = (selector: object) => {
-      return (
-        typeof selector === 'function' &&
-        'resultFunc' in selector &&
-        'memoizedResultFunc' in selector &&
-        'lastResult' in selector &&
-        'dependencies' in selector &&
-        'recomputations' in selector &&
-        'dependencyRecomputations' in selector &&
-        'resetRecomputations' in selector &&
-        'resetDependencyRecomputations' in selector &&
-        'memoize' in selector &&
-        'argsMemoize' in selector &&
-        typeof selector.resultFunc === 'function' &&
-        typeof selector.memoizedResultFunc === 'function' &&
-        typeof selector.lastResult === 'function' &&
-        Array.isArray(selector.dependencies) &&
-        typeof selector.recomputations === 'function' &&
-        typeof selector.dependencyRecomputations === 'function' &&
-        typeof selector.resetRecomputations === 'function' &&
-        typeof selector.resetDependencyRecomputations === 'function' &&
-        typeof selector.memoize === 'function' &&
-        typeof selector.argsMemoize === 'function' &&
-        selector.dependencies.length >= 1 &&
-        selector.dependencies.every(
-          (dependency): dependency is Function =>
-            typeof dependency === 'function'
-        ) &&
-        !selector.lastResult.length &&
-        !selector.recomputations.length &&
-        !selector.resetRecomputations.length &&
-        typeof selector.recomputations() === 'number'
-      )
-    }
     const isArrayOfFunctions = (array: any[]) =>
       array.every(e => typeof e === 'function')
-    expect(selectorDefault).toSatisfy(isMemoizedSelector)
+    expect(selectorDefault).toBeMemoizedSelector()
     expect(selectorDefault)
       .to.be.a('function')
       .that.has.all.keys(allFields)

test/setup.vitest.ts

@@ -0,0 +1,12 @@
+import { isMemoizedSelector } from './testUtils'
+
+expect.extend({
+  toBeMemoizedSelector(received) {
+    const { isNot } = this
+
+    return {
+      pass: isMemoizedSelector(received),
+      message: () => `${received} is${isNot ? '' : ' not'} a memoized selector`
+    }
+  }
+})

test/testUtils.ts

@@ -523,3 +523,38 @@ export const setEnvToProd = () => {
     process.env.NODE_ENV = originalEnv
   }
 }
+
+export const isMemoizedSelector = (selector: object) => {
+  return (
+    typeof selector === 'function' &&
+    'resultFunc' in selector &&
+    'memoizedResultFunc' in selector &&
+    'lastResult' in selector &&
+    'dependencies' in selector &&
+    'recomputations' in selector &&
+    'dependencyRecomputations' in selector &&
+    'resetRecomputations' in selector &&
+    'resetDependencyRecomputations' in selector &&
+    'memoize' in selector &&
+    'argsMemoize' in selector &&
+    typeof selector.resultFunc === 'function' &&
+    typeof selector.memoizedResultFunc === 'function' &&
+    typeof selector.lastResult === 'function' &&
+    Array.isArray(selector.dependencies) &&
+    typeof selector.recomputations === 'function' &&
+    typeof selector.dependencyRecomputations === 'function' &&
+    typeof selector.resetRecomputations === 'function' &&
+    typeof selector.resetDependencyRecomputations === 'function' &&
+    typeof selector.memoize === 'function' &&
+    typeof selector.argsMemoize === 'function' &&
+    selector.dependencies.length >= 1 &&
+    selector.dependencies.every(
+      (dependency): dependency is Function => typeof dependency === 'function'
+    ) &&
+    !selector.lastResult.length &&
+    !selector.recomputations.length &&
+    !selector.resetRecomputations.length &&
+    typeof selector.recomputations() === 'number' &&
+    typeof selector.dependencyRecomputations() === 'number'
+  )
+}

test/tsconfig.json

@@ -11,7 +11,7 @@
     "target": "ESNext",
     "jsx": "react",
     "baseUrl": ".",
-    "rootDir": ".",
+    "rootDir": "../",
     "skipLibCheck": true,
     "noImplicitReturns": false,
     "noUnusedLocals": false,
@@ -21,7 +21,5 @@
       "@internal/*": ["../src/*"]
     }
   },
-  "include": [
-    "**/*.ts*",
-  ]
+  "include": ["**/*.ts*"]
 }