createSlice: use template literal types for action type (#2250)

Author: phryneas

packages/toolkit/src/createSlice.ts

@@ -52,7 +52,7 @@ export interface Slice<
    * Action creators for the types of actions that are handled by the slice
    * reducer.
    */
-  actions: CaseReducerActions<CaseReducers>
+  actions: CaseReducerActions<CaseReducers, Name>
 
   /**
    * The individual case reducer functions that were passed in the `reducers` parameter.
@@ -165,38 +165,54 @@ export type SliceCaseReducers<State> = {
     | CaseReducerWithPrepare<State, PayloadAction<any, string, any, any>>
 }
 
+type SliceActionType<
+  SliceName extends string,
+  ActionName extends keyof any
+> = ActionName extends string | number ? `${SliceName}/${ActionName}` : string
+
 /**
  * Derives the slice's `actions` property from the `reducers` options
  *
  * @public
  */
-export type CaseReducerActions<CaseReducers extends SliceCaseReducers<any>> = {
+export type CaseReducerActions<
+  CaseReducers extends SliceCaseReducers<any>,
+  SliceName extends string
+> = {
   [Type in keyof CaseReducers]: CaseReducers[Type] extends { prepare: any }
-    ? ActionCreatorForCaseReducerWithPrepare<CaseReducers[Type]>
-    : ActionCreatorForCaseReducer<CaseReducers[Type]>
+    ? ActionCreatorForCaseReducerWithPrepare<
+        CaseReducers[Type],
+        SliceActionType<SliceName, Type>
+      >
+    : ActionCreatorForCaseReducer<
+        CaseReducers[Type],
+        SliceActionType<SliceName, Type>
+      >
 }
 
 /**
  * Get a `PayloadActionCreator` type for a passed `CaseReducerWithPrepare`
  *
  * @internal
  */
-type ActionCreatorForCaseReducerWithPrepare<CR extends { prepare: any }> =
-  _ActionCreatorWithPreparedPayload<CR['prepare'], string>
+type ActionCreatorForCaseReducerWithPrepare<
+  CR extends { prepare: any },
+  Type extends string
+> = _ActionCreatorWithPreparedPayload<CR['prepare'], Type>
 
 /**
  * Get a `PayloadActionCreator` type for a passed `CaseReducer`
  *
  * @internal
  */
-type ActionCreatorForCaseReducer<CR> = CR extends (
+type ActionCreatorForCaseReducer<CR, Type extends string> = CR extends (
   state: any,
   action: infer Action
 ) => any
   ? Action extends { payload: infer P }
-    ? PayloadActionCreator<P>
-    : ActionCreatorWithoutPayload
-  : ActionCreatorWithoutPayload
+    ? PayloadActionCreator<P, Type>
+    : ActionCreatorWithoutPayload<Type>
+  : ActionCreatorWithoutPayload<Type>
 
 /**
  * Extracts the CaseReducers out of a `reducers` object, even if they are

packages/toolkit/src/tests/createSlice.typetest.ts

@@ -154,12 +154,13 @@ const value = actionCreators.anyKey
     },
   })
 
-  const s: string = counter.actions.increment.type
-  const t: string = counter.actions.decrement.type
-  const u: string = counter.actions.multiply.type
+  const s: 'counter/increment' = counter.actions.increment.type
+  const sa: 'counter/increment' = counter.actions.increment().type
+  const t: 'counter/decrement' = counter.actions.decrement.type
+  const ta: 'counter/decrement' = counter.actions.decrement().type
+  const u: 'counter/multiply' = counter.actions.multiply.type
+  const ua: 'counter/multiply' = counter.actions.multiply(1).type
 
-  // @ts-expect-error
-  const x: 'counter/increment' = counter.actions.increment.type
   // @ts-expect-error
   const y: 'increment' = counter.actions.increment.type
 }
@@ -192,7 +193,9 @@ const value = actionCreators.anyKey
     },
   })
 
-  expectType<string>(counter.actions.incrementByStrLen('test').type)
+  expectType<'test/incrementByStrLen'>(
+    counter.actions.incrementByStrLen('test').type
+  )
   expectType<number>(counter.actions.incrementByStrLen('test').payload)
   expectType<string>(counter.actions.concatMetaStrLen('test').payload)
   expectType<number>(counter.actions.concatMetaStrLen('test').meta)
@@ -384,7 +387,7 @@ const value = actionCreators.anyKey
 
   const x: Action<unknown> = {} as any
   if (mySlice.actions.setName.match(x)) {
-    expectType<string>(x.type)
+    expectType<'name/setName'>(x.type)
     expectType<string>(x.payload)
   } else {
     // @ts-expect-error