fn -> to

Author: davidkpiano

packages/core/src/StateNode.ts

@@ -369,7 +369,7 @@ export class StateNode<
             transition.target ||
             // transition.actions.length ||
             transition.reenter ||
-            transition.fn
+            transition.to
         );
       })
     );

packages/core/src/stateUtils.ts

@@ -270,7 +270,7 @@ export function getDelayedTransitions(
       typeof configTransition === 'string'
         ? { target: configTransition }
         : typeof configTransition === 'function'
-          ? { fn: configTransition }
+          ? { to: configTransition }
           : configTransition;
     const resolvedDelay = Number.isNaN(+delay) ? delay : +delay;
     const eventType = mutateEntryExitWithDelay(resolvedDelay);
@@ -1254,7 +1254,7 @@ export function getTransitionResult(
   reenter?: boolean;
   internalEvents: EventObject[] | undefined;
 } {
-  if (transition.fn) {
+  if (transition.to) {
     const actions: UnknownAction[] = [];
     const internalEvents: EventObject[] = [];
     const enqueue = createEnqueueObject(
@@ -1339,7 +1339,7 @@ export function getTransitionResult(
       }
     );
 
-    const res = transition.fn(
+    const res = transition.to(
       {
         context: snapshot.context,
         event,
@@ -2167,7 +2167,7 @@ export function hasEffect(
   snapshot: AnyMachineSnapshot,
   self: AnyActorRef
 ): boolean {
-  if (transition.fn) {
+  if (transition.to) {
     let hasEffect = false;
     let res;
 
@@ -2176,7 +2176,7 @@ export function hasEffect(
         hasEffect = true;
         throw new Error('Effect triggered');
       };
-      res = transition.fn(
+      res = transition.to(
         {
           context,
           event,
@@ -2224,7 +2224,7 @@ export function evaluateCandidate(
   stateNode: AnyStateNode,
   self: AnyActorRef
 ): boolean {
-  if (candidate.fn) {
+  if (candidate.to) {
     let hasEffect = false;
     let res;
     const context = snapshot.context;
@@ -2234,7 +2234,7 @@ export function evaluateCandidate(
         hasEffect = true;
         throw new Error('Effect triggered');
       };
-      res = candidate.fn(
+      res = candidate.to(
         {
           context,
           event,

packages/core/src/types.ts

@@ -252,7 +252,7 @@ export interface TransitionConfig<
   actions?: never;
   reenter?: boolean;
   target?: TransitionTarget | undefined;
-  fn?: TransitionConfigFunction<
+  to?: TransitionConfigFunction<
     TContext,
     TExpressionEvent,
     TEvent,

packages/core/src/types.v6.ts

@@ -417,7 +417,28 @@ export type Next_TransitionConfigOrTarget<
 > =
   | string
   | undefined
-  | { target?: string | string[]; description?: string; reenter?: boolean }
+  | {
+      target?: string | string[];
+      description?: string;
+      reenter?: boolean;
+      meta?: TMeta;
+    }
+  | {
+      to?: TransitionConfigFunction<
+        TContext,
+        TExpressionEvent,
+        TEvent,
+        TEmitted,
+        TActionMap,
+        TActorMap,
+        TGuardMap,
+        TDelayMap,
+        TMeta
+      >;
+      description?: string;
+      reenter?: boolean;
+      meta?: TMeta;
+    }
   | TransitionConfigFunction<
       TContext,
       TExpressionEvent,

packages/core/src/utils.ts

@@ -232,7 +232,7 @@ export function toTransitionConfigArray(
     }
 
     if (typeof transitionLike === 'function') {
-      return { fn: transitionLike };
+      return { to: transitionLike };
     }
 
     return transitionLike;

packages/core/test/transition.test.ts

@@ -584,4 +584,32 @@ describe('transition function', () => {
     await sleep(10);
     expect(JSON.parse(db.state).value).toBe('finish');
   });
+
+  it('should support transition functions', () => {
+    const fn = vi.fn();
+    const machine = createMachine({
+      initial: 'a',
+      states: {
+        a: {
+          on: {
+            NEXT: {
+              description: 'next',
+              to: (_, enq) => {
+                enq(fn);
+                return {
+                  target: 'b'
+                };
+              }
+            }
+          }
+        },
+        b: {}
+      }
+    });
+
+    const [init] = initialTransition(machine);
+    const [s1, actions] = transition(machine, init, { type: 'NEXT' });
+    expect(s1.value).toEqual('b');
+    expect(actions.length).toEqual(1);
+  });
 });