Remove initial state getter from machines and require actor context f…

…or `transition`/`getInitialState` calls (#4018)

* Remove initialState getter

* add changesets

.changeset/happy-kings-destroy.md

@@ -0,0 +1,5 @@
+---
+'xstate': major
+---
+
+`machine.initialState` has been removed, you can use `machine.getInitialState(...)` instead

.changeset/itchy-owls-swim.md

@@ -0,0 +1,5 @@
+---
+'xstate': major
+---
+
+`machine.transition(...)` and `machine.getInitialState(...)` require now an `actorContext` argument

.changeset/odd-zoos-heal.md

@@ -0,0 +1,5 @@
+---
+'xstate': major
+---
+
+`machine.transition` no longer accepts state values. You have to resolve the state value to a `State` before passing it to `machine.transition`

packages/core/src/StateMachine.ts

@@ -231,22 +231,19 @@ export class StateMachine<
    * @param event The received event
    */
   public transition(
-    state: State<TContext, TEvent, TResolvedTypesMeta> | StateValue = this
-      .initialState,
+    state: State<TContext, TEvent, TResolvedTypesMeta>,
     event: TEvent,
-    actorCtx?: ActorContext<TEvent, State<TContext, TEvent, any>>
+    actorCtx: ActorContext<TEvent, State<TContext, TEvent, any>>
   ): State<TContext, TEvent, TResolvedTypesMeta> {
-    const currentState =
-      state instanceof State ? state : this.resolveStateValue(state);
     // TODO: handle error events in a better way
     if (
       isErrorEvent(event) &&
-      !currentState.nextEvents.some((nextEvent) => nextEvent === event.type)
+      !state.nextEvents.some((nextEvent) => nextEvent === event.type)
     ) {
       throw event.data;
     }
 
-    const { state: nextState } = macrostep(currentState, event, actorCtx);
+    const { state: nextState } = macrostep(state, event, actorCtx);
 
     return nextState;
   }
@@ -259,9 +256,9 @@ export class StateMachine<
    * @param event The received event
    */
   public microstep(
-    state: State<TContext, TEvent, TResolvedTypesMeta> = this.initialState,
+    state: State<TContext, TEvent, TResolvedTypesMeta>,
     event: TEvent,
-    actorCtx?: AnyActorContext | undefined
+    actorCtx: AnyActorContext
   ): Array<State<TContext, TEvent, TResolvedTypesMeta>> {
     return macrostep(state, event, actorCtx).microstates;
   }
@@ -278,7 +275,7 @@ export class StateMachine<
    * This "pre-initial" state is provided to initial actions executed in the initial state.
    */
   private getPreInitialState(
-    actorCtx: AnyActorContext | undefined,
+    actorCtx: AnyActorContext,
     input: any
   ): State<TContext, TEvent, TResolvedTypesMeta> {
     const [context, actions] = this.getContextAndActions(actorCtx, input);
@@ -312,22 +309,11 @@ export class StateMachine<
     return preInitial;
   }
 
-  /**
-   * The initial State instance, which includes all actions to be executed from
-   * entering the initial state.
-   */
-  public get initialState(): State<TContext, TEvent, TResolvedTypesMeta> {
-    return this.getInitialState();
-  }
-
   /**
    * Returns the initial `State` instance, with reference to `self` as an `ActorRef`.
    */
   public getInitialState(
-    actorCtx?: ActorContext<
-      TEvent,
-      State<TContext, TEvent, TResolvedTypesMeta>
-    >,
+    actorCtx: ActorContext<TEvent, State<TContext, TEvent, TResolvedTypesMeta>>,
     input?: any
   ): State<TContext, TEvent, TResolvedTypesMeta> {
     const initEvent = createInitEvent(input) as unknown as TEvent; // TODO: fix;

packages/core/src/actors/callback.ts

@@ -18,7 +18,7 @@ export interface CallbackInternalState {
 
 export function fromCallback<TEvent extends EventObject>(
   invokeCallback: InvokeCallback
-): ActorBehavior<TEvent, undefined> {
+): ActorBehavior<TEvent, undefined, CallbackInternalState> {
   const behavior: ActorBehavior<TEvent, undefined, CallbackInternalState> = {
     config: invokeCallback,
     start: (_state, { self }) => {

packages/core/src/actors/observable.ts

@@ -137,7 +137,12 @@ export function fromObservable<T, TEvent extends EventObject>(
 
 export function fromEventObservable<T extends EventObject>(
   lazyObservable: ({ input }: { input: any }) => Subscribable<T>
-): ActorBehavior<EventObject, T | undefined> {
+): ActorBehavior<
+  EventObject,
+  T | undefined,
+  ObservableInternalState<T>,
+  ObservablePersistedState<T>
+> {
   const errorEventType = '$$xstate.error';
   const completeEventType = '$$xstate.complete';
 

packages/core/src/stateUtils.ts

@@ -46,14 +46,12 @@ import {
   AnyEventObject,
   AnyHistoryValue,
   AnyState,
-  AnyStateMachine,
   AnyStateNode,
   AnyTransitionDefinition,
   DelayedTransitionDefinition,
   HistoryValue,
   InitialTransitionDefinition,
-  SendActionObject,
-  StateFromMachine
+  SendActionObject
 } from '.';
 import { stopSignalType } from './actors/index.ts';
 import { ActorStatus } from './interpreter.ts';
@@ -1031,7 +1029,7 @@ export function microstep<
 >(
   transitions: Array<TransitionDefinition<TContext, TEvent>>,
   currentState: State<TContext, TEvent, any>,
-  actorCtx: AnyActorContext | undefined,
+  actorCtx: AnyActorContext,
   event: TEvent
 ): State<TContext, TEvent, any> {
   const { machine } = currentState;
@@ -1120,7 +1118,7 @@ function microstepProcedure(
   currentState: AnyState,
   mutConfiguration: Set<AnyStateNode>,
   event: AnyEventObject,
-  actorCtx: AnyActorContext | undefined
+  actorCtx: AnyActorContext
 ): typeof currentState {
   const actions: BaseActionObject[] = [];
   const historyValue = {
@@ -1541,10 +1539,10 @@ export function resolveActionsAndContext<
   };
 }
 
-export function macrostep<TMachine extends AnyStateMachine>(
-  state: StateFromMachine<TMachine>,
-  event: TMachine['__TEvent'],
-  actorCtx: AnyActorContext | undefined
+export function macrostep(
+  state: AnyState,
+  event: EventObject,
+  actorCtx: AnyActorContext
 ): {
   state: typeof state;
   microstates: Array<typeof state>;
@@ -1554,7 +1552,7 @@ export function macrostep<TMachine extends AnyStateMachine>(
   }
 
   let nextState = state;
-  const states: StateFromMachine<TMachine>[] = [];
+  const states: AnyState[] = [];
 
   // Handle stop event
   if (event.type === stopSignalType) {
@@ -1630,7 +1628,7 @@ export function macrostep<TMachine extends AnyStateMachine>(
 function stopStep(
   event: AnyEventObject,
   nextState: AnyState,
-  actorCtx: AnyActorContext | undefined
+  actorCtx: AnyActorContext
 ): AnyState {
   const actions: BaseActionObject[] = [];
 

packages/core/src/types.ts

@@ -130,7 +130,13 @@ export type Spawner = <T extends ActorBehavior<any, any> | string>( // TODO: rea
     systemId?: string;
     input: any;
   }>
-) => T extends ActorBehavior<infer TActorEvent, infer TActorEmitted>
+) => T extends ActorBehavior<
+  infer TActorEvent,
+  infer TActorEmitted,
+  infer _,
+  infer __,
+  infer ___
+>
   ? ActorRef<TActorEvent, TActorEmitted>
   : ActorRef<any, any>; // TODO: narrow this to behaviors from machine
 
@@ -1758,7 +1764,7 @@ export type AnyActorContext = ActorContext<any, any, any>;
 export interface ActorBehavior<
   TEvent extends EventObject,
   TSnapshot = any,
-  TInternalState = any,
+  TInternalState = TSnapshot,
   /**
    * Serialized internal state used for persistence & restoration
    */
@@ -1820,7 +1826,15 @@ export type SnapshotFrom<T> = ReturnTypeOrValue<T> extends infer R
   : never;
 
 export type EventFromBehavior<TBehavior extends ActorBehavior<any, any>> =
-  TBehavior extends ActorBehavior<infer TEvent, infer _> ? TEvent : never;
+  TBehavior extends ActorBehavior<
+    infer TEvent,
+    infer _,
+    infer __,
+    infer ___,
+    infer ____
+  >
+    ? TEvent
+    : never;
 
 export type PersistedStateFrom<TBehavior extends ActorBehavior<any, any>> =
   TBehavior extends ActorBehavior<
@@ -1896,9 +1910,6 @@ export type TagsFrom<TMachine extends AnyStateMachine> = Parameters<
   StateFrom<TMachine>['hasTag']
 >[0];
 
-export type StateFromMachine<TMachine extends AnyStateMachine> =
-  TMachine['initialState'];
-
 export interface ActorSystemInfo {
   actors: Record<string, AnyActorRef>;
 }

packages/core/test/actions.test.ts

@@ -913,8 +913,8 @@ describe('entry/exit actions', () => {
 
       const flushTracked = trackEntries(machine);
 
-      const aa1State = machine.resolveStateValue({ A: 'A1' });
-      const service = interpret(machine, { state: aa1State }).start();
+      const service = interpret(machine).start();
+      flushTracked();
       service.send({ type: 'NEXT' });
 
       expect(flushTracked()).toEqual([
@@ -2231,9 +2231,11 @@ describe('actions config', () => {
         }
       }
     );
-    const state = machine.transition('a', { type: 'EVENT' });
+    const actorRef = interpret(machine).start();
+    actorRef.send({ type: 'EVENT' });
+    const snapshot = actorRef.getSnapshot();
 
-    // expect(state.actions).toEqual([
+    // expect(snapshot.actions).toEqual([
     //   expect.objectContaining({
     //     type: 'definedAction'
     //   }),
@@ -2243,7 +2245,7 @@ describe('actions config', () => {
     // ]);
     // TODO: specify which actions other actions came from
 
-    expect(state.context).toEqual({ count: 10 });
+    expect(snapshot.context).toEqual({ count: 10 });
   });
 
   it('should work with anonymous functions (with warning)', () => {

packages/core/test/actor.test.ts

@@ -849,10 +849,10 @@ describe('actors', () => {
       }
     });
 
-    const { initialState } = nullActorMachine;
-
-    // expect(initialState.context.ref!.id).toBe('null'); // TODO: identify null actors
-    expect(initialState.context.ref!.send).toBeDefined();
+    // expect(interpret(nullActorMachine).getSnapshot().context.ref!.id).toBe('null'); // TODO: identify null actors
+    expect(
+      interpret(nullActorMachine).getSnapshot().context.ref!.send
+    ).toBeDefined();
   });
 
   describe('with behaviors', () => {