[core] Transition function

.changeset/lemon-needles-play.md

@@ -0,0 +1,23 @@
+---
+'xstate': minor
+---
+
+Added a new `transition` function that takes an actor logic, a snapshot, and an event, and returns a tuple containing the next snapshot and the actions to execute. This function is a pure function and does not execute the actions itself. It can be used like this:
+
+```ts
+import { transition } from 'xstate';
+
+const [nextState, actions] = transition(actorLogic, currentState, event);
+// Execute actions as needed
+```
+
+Added a new `initialTransition` function that takes an actor logic and an optional input, and returns a tuple containing the initial snapshot and the actions to execute from the initial transition. This function is also a pure function and does not execute the actions itself. It can be used like this:
+
+```ts
+import { initialTransition } from 'xstate';
+
+const [initialState, actions] = initialTransition(actorLogic, input);
+// Execute actions as needed
+```
+
+These new functions provide a way to separate the calculation of the next snapshot and actions from the execution of those actions, allowing for more control and flexibility in the transition process.

.vscode/launch.json

@@ -11,7 +11,7 @@
       "console": "integratedTerminal",
       "internalConsoleOptions": "neverOpen",
       "windows": {
-        "program": "${workspaceFolder}/node_modules/jest/bin/jest"
+        "program": "${workspaceFolder}/node_modules/jest/bin/jest.js"
       }
     },
     {
@@ -30,7 +30,7 @@
       "console": "integratedTerminal",
       "internalConsoleOptions": "neverOpen",
       "windows": {
-        "program": "${workspaceFolder}/node_modules/jest/bin/jest"
+        "program": "${workspaceFolder}/node_modules/jest/bin/jest.js"
       }
     }
   ]

README.md

@@ -181,16 +181,16 @@ Read [📽 the slides](http://slides.com/davidkhourshid/finite-state-machines) (
 
 ## Packages
 
-| Package                                                                                       | Description                                                                  |
-| --------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------- |
-| 🤖 `xstate`                                                                                   | Core finite state machine and statecharts library + interpreter              |
-| [📉 `@xstate/graph`](https://github.com/statelyai/xstate/tree/main/packages/xstate-graph)     | Graph traversal and model-based testing utilities using XState               |
-| [⚛️ `@xstate/react`](https://github.com/statelyai/xstate/tree/main/packages/xstate-react)     | React hooks and utilities for using XState in React applications             |
-| [💚 `@xstate/vue`](https://github.com/statelyai/xstate/tree/main/packages/xstate-vue)         | Vue composition functions and utilities for using XState in Vue applications |
-| [🎷 `@xstate/svelte`](https://github.com/statelyai/xstate/tree/main/packages/xstate-svelte)   | Svelte utilities for using XState in Svelte applications                     |
-| [🥏 `@xstate/solid`](https://github.com/statelyai/xstate/tree/main/packages/xstate-solid)     | Solid hooks and utilities for using XState in Solid applications             |
-| [🔍 `@statelyai/inspect`](https://github.com/statelyai/inspect) | Inspection utilities for XState                                              |
-| [🏪 `@xstate/store`](https://github.com/statelyai/xstate/tree/main/packages/xstate-store) | Small library for simple state management |
+| Package                                                                                     | Description                                                                  |
+| ------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------- |
+| 🤖 `xstate`                                                                                 | Core finite state machine and statecharts library + interpreter              |
+| [📉 `@xstate/graph`](https://github.com/statelyai/xstate/tree/main/packages/xstate-graph)   | Graph traversal and model-based testing utilities using XState               |
+| [⚛️ `@xstate/react`](https://github.com/statelyai/xstate/tree/main/packages/xstate-react)   | React hooks and utilities for using XState in React applications             |
+| [💚 `@xstate/vue`](https://github.com/statelyai/xstate/tree/main/packages/xstate-vue)       | Vue composition functions and utilities for using XState in Vue applications |
+| [🎷 `@xstate/svelte`](https://github.com/statelyai/xstate/tree/main/packages/xstate-svelte) | Svelte utilities for using XState in Svelte applications                     |
+| [🥏 `@xstate/solid`](https://github.com/statelyai/xstate/tree/main/packages/xstate-solid)   | Solid hooks and utilities for using XState in Solid applications             |
+| [🔍 `@statelyai/inspect`](https://github.com/statelyai/inspect)                             | Inspection utilities for XState                                              |
+| [🏪 `@xstate/store`](https://github.com/statelyai/xstate/tree/main/packages/xstate-store)   | Small library for simple state management                                    |
 
 ## Finite State Machines
 

jest.config.js

@@ -3,7 +3,7 @@ const { constants } = require('jest-config');
 /** @type {import('@jest/types').Config.InitialOptions} */
 module.exports = {
   prettierPath: null,
-  setupFilesAfterEnv: ['@xstate-repo/jest-utils/setup'],
+  setupFilesAfterEnv: ['<rootDir>/scripts/jest-utils/setup'],
   transform: {
     [constants.DEFAULT_JS_PATTERN]: 'babel-jest',
     '^.+\\.vue$': '@vue/vue3-jest',

packages/core/src/StateMachine.ts

@@ -1,5 +1,9 @@
 import isDevelopment from '#is-development';
 import { assign } from './actions.ts';
+import { executeCancel } from './actions/cancel.ts';
+import { executeRaise } from './actions/raise.ts';
+import { executeSendTo } from './actions/send.ts';
+import { createEmptyActor } from './actors/index.ts';
 import { $$ACTOR_TYPE, createActor } from './createActor.ts';
 import { createInitEvent } from './eventUtils.ts';
 import {
@@ -18,6 +22,7 @@ import {
   macrostep,
   microstep,
   resolveActionsAndContext,
+  resolveReferencedAction,
   resolveStateValue,
   transitionNode
 } from './stateUtils.ts';
@@ -48,7 +53,8 @@ import type {
   TransitionDefinition,
   ResolvedStateMachineTypes,
   StateSchema,
-  SnapshotStatus
+  SnapshotStatus,
+  ExecutableActionObject
 } from './types.ts';
 import { resolveReferencedActor, toStatePath } from './utils.ts';
 
@@ -293,7 +299,8 @@ export class StateMachine<
     TMeta,
     TConfig
   > {
-    return macrostep(snapshot, event, actorScope).snapshot as typeof snapshot;
+    return macrostep(snapshot, event, actorScope, [])
+      .snapshot as typeof snapshot;
   }
 
   /**
@@ -328,7 +335,7 @@ export class StateMachine<
       TConfig
     >
   > {
-    return macrostep(snapshot, event, actorScope).microstates;
+    return macrostep(snapshot, event, actorScope, []).microstates;
   }
 
   public getTransitionData(
@@ -386,7 +393,8 @@ export class StateMachine<
         initEvent,
         actorScope,
         [assign(assignment)],
-        internalQueue
+        internalQueue,
+        undefined
       ) as SnapshotFrom<this>;
     }
 
@@ -629,4 +637,57 @@ export class StateMachine<
 
     return restoredSnapshot;
   }
+
+  /**
+   * Runs an executable action. Executable actions are returned from the
+   * `transition(…)` function.
+   *
+   * @example
+   *
+   * ```ts
+   * const [state, actions] = transition(someMachine, someState, someEvent);
+   *
+   * for (const action of actions) {
+   *   // Executes the action
+   *   someMachine.executeAction(action);
+   * }
+   * ```
+   */
+  public executeAction(
+    action: ExecutableActionObject,
+    actor: AnyActorRef = createEmptyActor()
+  ) {
+    const actorScope = (actor as any)._actorScope as AnyActorScope;
+    const defer = actorScope.defer;
+    actorScope.defer = (fn) => fn();
+    try {
+      switch (action.type) {
+        case 'xstate.cancel':
+          executeCancel(actorScope, action.params as any);
+          return;
+        case 'xstate.raise':
+          if (typeof (action as any).params.delay !== 'number') {
+            return;
+          }
+          executeRaise(actorScope, action.params as any);
+          return;
+        case 'xstate.sendTo':
+          executeSendTo(actorScope, action.params as any);
+          return;
+      }
+      const resolvedInfo = {
+        ...action.info,
+        self: actor,
+        system: actor.system
+      };
+      if (action.exec) {
+        action.exec?.(resolvedInfo, action.params);
+      } else {
+        const resolvedAction = resolveReferencedAction(this, action.type)!;
+        resolvedAction(resolvedInfo, action.params);
+      }
+    } finally {
+      actorScope.defer = defer;
+    }
+  }
 }

packages/core/src/StateNode.ts

@@ -4,6 +4,7 @@ import { NULL_EVENT, STATE_DELIMITER } from './constants.ts';
 import { evaluateGuard } from './guards.ts';
 import { memo } from './memo.ts';
 import {
+  BuiltinAction,
   formatInitialTransition,
   formatTransition,
   formatTransitions,
@@ -47,7 +48,7 @@ const toSerializableAction = (action: UnknownAction) => {
   }
   if (typeof action === 'function') {
     if ('resolve' in action) {
-      return { type: (action as any).type };
+      return { type: (action as BuiltinAction).type };
     }
     return {
       type: action.name
@@ -261,7 +262,7 @@ export class StateNode<
       on: this.on,
       transitions: [...this.transitions.values()].flat().map((t) => ({
         ...t,
-        actions: t.actions.map(toSerializableAction)
+        actions: t.actions
       })),
       entry: this.entry.map(toSerializableAction),
       exit: this.exit.map(toSerializableAction),
@@ -296,21 +297,22 @@ export class StateNode<
       toArray(this.config.invoke).map((invokeConfig, i) => {
         const { src, systemId } = invokeConfig;
         const resolvedId = invokeConfig.id ?? createInvokeId(this.id, i);
-        const resolvedSrc =
+        const sourceName =
           typeof src === 'string'
             ? src
             : `xstate.invoke.${createInvokeId(this.id, i)}`;
+
         return {
           ...invokeConfig,
-          src: resolvedSrc,
+          src: sourceName,
           id: resolvedId,
           systemId: systemId,
           toJSON() {
             const { onDone, onError, ...invokeDefValues } = invokeConfig;
             return {
               ...invokeDefValues,
               type: 'xstate.invoke',
-              src: resolvedSrc,
+              src: sourceName,
               id: resolvedId
             };
           }

packages/core/src/actions/assign.ts

@@ -1,7 +1,7 @@
 import isDevelopment from '#is-development';
 import { cloneMachineSnapshot } from '../State.ts';
+import { executingCustomAction } from '../createActor.ts';
 import { Spawner, createSpawner } from '../spawn.ts';
-import { executingCustomAction } from '../stateUtils.ts';
 import type {
   ActionArgs,
   AnyActorScope,

packages/core/src/actions/cancel.ts

@@ -5,7 +5,8 @@ import {
   EventObject,
   MachineContext,
   ActionArgs,
-  ParameterizedObject
+  ParameterizedObject,
+  SpecialActionResolution
 } from '../types.ts';
 
 type ResolvableSendId<
@@ -26,15 +27,18 @@ function resolveCancel(
   actionArgs: ActionArgs<any, any, any>,
   actionParams: ParameterizedObject['params'] | undefined,
   { sendId }: { sendId: ResolvableSendId<any, any, any, any> }
-) {
+): SpecialActionResolution {
   const resolvedSendId =
     typeof sendId === 'function' ? sendId(actionArgs, actionParams) : sendId;
-  return [snapshot, resolvedSendId];
+  return [snapshot, { sendId: resolvedSendId }];
 }
 
-function executeCancel(actorScope: AnyActorScope, resolvedSendId: string) {
+export function executeCancel(
+  actorScope: AnyActorScope,
+  params: { sendId: string }
+) {
   actorScope.defer(() => {
-    actorScope.system.scheduler.cancel(actorScope.self, resolvedSendId);
+    actorScope.system.scheduler.cancel(actorScope.self, params.sendId);
   });
 }
 

packages/core/src/actions/emit.ts

@@ -1,5 +1,5 @@
 import isDevelopment from '#is-development';
-import { executingCustomAction } from '../stateUtils.ts';
+import { executingCustomAction } from '../createActor.ts';
 import {
   ActionArgs,
   ActionFunction,

packages/core/src/actions/raise.ts

@@ -1,5 +1,5 @@
 import isDevelopment from '#is-development';
-import { executingCustomAction } from '../stateUtils.ts';
+import { executingCustomAction } from '../createActor.ts';
 import {
   ActionArgs,
   ActionFunction,
@@ -9,6 +9,7 @@ import {
   DelayExpr,
   DoNotInfer,
   EventObject,
+  ExecutableActionObject,
   MachineContext,
   ParameterizedObject,
   RaiseActionOptions,
@@ -75,10 +76,17 @@ function resolveRaise(
   if (typeof resolvedDelay !== 'number') {
     internalQueue.push(resolvedEvent);
   }
-  return [snapshot, { event: resolvedEvent, id, delay: resolvedDelay }];
+  return [
+    snapshot,
+    {
+      event: resolvedEvent,
+      id,
+      delay: resolvedDelay
+    }
+  ];
 }
 
-function executeRaise(
+export function executeRaise(
   actorScope: AnyActorScope,
   params: {
     event: EventObject;
@@ -168,3 +176,12 @@ export function raise<
 
   return raise;
 }
+
+export interface ExecutableRaiseAction extends ExecutableActionObject {
+  type: 'xstate.raise';
+  params: {
+    event: EventObject;
+    id: string | undefined;
+    delay: number | undefined;
+  };
+}