Passed state type generic to the Config interface

statelyai · Apr 10, 2020 · dcbd72f · dcbd72f
1 parent 7f08309
commit dcbd72f
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Showing 4 changed files with 21 additions and 4 deletions.
diff --git a/.changeset/wise-lemons-travel.md b/.changeset/wise-lemons-travel.md
@@ -0,0 +1,5 @@
+---
+'@xstate/fsm': patch
+---
+
+Passed state type generic to the Config interface
diff --git a/packages/xstate-fsm/src/index.ts b/packages/xstate-fsm/src/index.ts
@@ -81,7 +81,7 @@ export function createMachine<
   TEvent extends EventObject = EventObject,
   TState extends Typestate<TContext> = any
 >(
-  fsmConfig: StateMachine.Config<TContext, TEvent>,
+  fsmConfig: StateMachine.Config<TContext, TEvent, TState>,
   options: {
     actions?: StateMachine.ActionMap<TContext, TEvent>;
   } = {}

diff --git a/packages/xstate-fsm/src/types.ts b/packages/xstate-fsm/src/types.ts
@@ -68,12 +68,16 @@ export namespace StateMachine {
     ) => this is TState extends { value: TSV } ? TState : never;
   }
 
-  export interface Config<TContext extends object, TEvent extends EventObject> {
+  export interface Config<
+    TContext extends object,
+    TEvent extends EventObject,
+    TState extends Typestate<TContext> = any
+  > {
     id?: string;
     initial: string;
     context?: TContext;
     states: {
-      [key: string]: {
+      [key in TState['value']]: {
         on?: {
           [K in TEvent['type']]?: SingleOrArray<
             Transition<TContext, TEvent extends { type: K } ? TEvent : never>

diff --git a/packages/xstate-fsm/test/fsm.test.ts b/packages/xstate-fsm/test/fsm.test.ts
@@ -20,9 +20,17 @@ describe('@xstate/fsm', () => {
     | {
         value: 'yellow';
         context: LightContext & { go: false };
+      }
+    | {
+        value: 'red';
+        context: LightContext & { go: false };
       };
 
-  const lightConfig: StateMachine.Config<LightContext, LightEvent> = {
+  const lightConfig: StateMachine.Config<
+    LightContext,
+    LightEvent,
+    LightState
+  > = {
     id: 'light',
     initial: 'green',
     context: { count: 0, foo: 'bar', go: true },