Fix issues with createStructuredSelector parameters

src/index.ts

@@ -7,7 +7,9 @@ import type {
   DropFirst,
   MergeParameters,
   Expand,
-  ObjValueTuple
+  ObjValueTuple,
+  Head,
+  Tail
 } from './types'
 
 export type {
@@ -213,13 +215,19 @@ export const createSelector =
 type SelectorsObject = { [key: string]: (...args: any[]) => any }
 
 export interface StructuredSelectorCreator {
-  <SelectorMap extends SelectorsObject>(
+  <
+    SelectorMap extends SelectorsObject,
+    SelectorParams = MergeParameters<ObjValueTuple<SelectorMap>>
+  >(
     selectorMap: SelectorMap,
     selectorCreator?: CreateSelectorFunction<any, any, any>
   ): (
     // Accept an arbitrary number of parameters for all selectors
-    // @ts-ignore
-    ...params: [...MergeParameters<ObjValueTuple<SelectorMap>>]
+    // The annoying head/tail bit here is because TS isn't convinced that
+    // the `SelectorParams` type is really an array, so we launder things.
+    // Plus it matches common usage anyway.
+    state: Head<SelectorParams>,
+    ...params: Tail<SelectorParams>
   ) => {
     [Key in keyof SelectorMap]: ReturnType<SelectorMap[Key]>
   }

src/types.ts

@@ -179,7 +179,7 @@ export type ExpandItems<T extends readonly unknown[]> = {
 }
 
 /** First item in an array */
-export type Head<T extends any[]> = T extends [any, ...any[]] ? T[0] : never
+export type Head<T> = T extends [any, ...any[]] ? T[0] : never
 /** All other items in an array */
 export type Tail<A> = A extends [any, ...infer Rest] ? Rest : never
 

typescript_test/test.ts

@@ -608,6 +608,16 @@ function testCreateSelectorCreator() {
 }
 
 function testCreateStructuredSelector() {
+  const oneParamSelector = createStructuredSelector({
+    foo: (state: StateAB) => state.a,
+    bar: (state: StateAB) => state.b
+  })
+
+  const threeParamSelector = createStructuredSelector({
+    foo: (state: StateAB, c: number, d: string) => state.a,
+    bar: (state: StateAB, c: number, d: string) => state.b
+  })
+
   const selector = createStructuredSelector<
     { foo: string },
     {
@@ -619,9 +629,9 @@ function testCreateStructuredSelector() {
     bar: state => +state.foo
   })
 
-  const res = selector({ foo: '42' })
-  const foo: string = res.foo
-  const bar: number = res.bar
+  const res1 = selector({ foo: '42' })
+  const foo: string = res1.foo
+  const bar: number = res1.bar
 
   // @ts-expect-error
   selector({ bar: '42' })
@@ -646,8 +656,8 @@ function testCreateStructuredSelector() {
 
   // Test automatic inference of types for createStructuredSelector via overload
   type State = { foo: string }
-  const FooSelector = (state: State) => state.foo
-  const BarSelector = (state: State) => +state.foo
+  const FooSelector = (state: State, a: number, b: string) => state.foo
+  const BarSelector = (state: State, a: number, b: string) => +state.foo
 
   const selector2 = createStructuredSelector({
     foo: FooSelector,
@@ -667,8 +677,15 @@ function testCreateStructuredSelector() {
     bar: number
   }
 
+  const resOneParam = oneParamSelector({ a: 1, b: 2 })
+  const resThreeParams = threeParamSelector({ a: 1, b: 2 }, 99, 'blah')
   const res2: ExpectedResult = selector({ foo: '42' })
-  const resGenerics: ExpectedResult = selectorGenerics({ foo: '42' })
+  const res3: ExpectedResult = selector2({ foo: '42' }, 99, 'test')
+  const resGenerics: ExpectedResult = selectorGenerics(
+    { foo: '42' },
+    99,
+    'test'
+  )
 
   //@ts-expect-error
   selector2({ bar: '42' })