[core] Transition function (#4954)

* Use defaultActionExecutor (temp)

* Convert entry/exit events

* UnknownAction -> UnknownActionObject

* Use defaultActionExecutor

* Cleanup

* WIP

* Fixing tests

* Add toJSON to built-in actions

* Add docs

* Update packages/core/src/actions/spawnChild.ts

Co-authored-by: Mateusz Burzyński <[email protected]>

* Update packages/core/src/stateUtils.ts

Co-authored-by: Mateusz Burzyński <[email protected]>

* Unify convertAction

* Update packages/core/src/stateUtils.ts

Co-authored-by: Mateusz Burzyński <[email protected]>

* Remove TODO

* Introduce `executeAction`, remove `action.execute()`

* Enqueue actions test

* Fix type error

* Expose `executeAction(…)`

* Provide actor to action

* Fix type issue

* Changeset

* Deprecate getNextSnapshot and getInitialSnapshot

* Update packages/core/src/stateUtils.ts

Co-authored-by: Mateusz Burzyński <[email protected]>

* Restore getNextSnapshot.test.ts file

* function -> exec

* Delayed raise action test

* Getting close

* Update scheduler to handle delayed sendTo actions without an initially resolved target

* Fix types

* WIP

* Remove test code

* Default actor

* Serialization in test

* Revert invoke.test.ts

* Cancel action execution

* WIP

* Update launch.json and jest.config.js

* Proof of concept for invoked actions

* Include resolved input & systemId in spawnChild action

* Refactor action types to use ExecutableActionObject and add startedAt timestamp to raise and send actions

* Add ExecutableActionsFrom

* Clean up types

* Lint

* Lint for real

* Lint lint

* Back to any

* Update packages/core/test/transition.test.ts

Co-authored-by: Mateusz Burzyński <[email protected]>

* use sleep

* remove outdated comment

* add `ExecutableSendToAction` to `SpecialExecutableAction`

* remove `startedAt`

* add failing raise test case

* tweak test title

* add extra cancel tests

* add failing test for invalid event delivery

* Revert test (happens in main)

* Remove invalid test: The <cancel> element is used to cancel a delayed <send> event.

* Fixed tests

* remove unused import

* add warn assertions

* Revert "Remove invalid test: The <cancel> element is used to cancel a delayed <send> event."

This reverts commit ab4bad0.

* make it green, make it green

* add action resolution capabilities to machine.executeAction

* share `resolvedInfo` between branches

* bring back `ExecutableActionObject['exec']`

* add a failing boilerplate for `cancel` execution

* Fix cancel action

* Add SpecialActionResolution type

* Add test for sendTo action

* actorId -> targetId

* Rename

* Add tests for emit and log

* Remove switch statement in executeAction

* Undo

* Remove executeAction for now

* bring back one `toSerializableAction` call

* fix one type issue

* tweak test titles

* remove redundant test

* dont export `getAction`

---------

Co-authored-by: Mateusz Burzyński <[email protected]>

Author: davidkpiano

.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

@@ -293,7 +293,8 @@ 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 +329,7 @@ export class StateMachine<
       TConfig
     >
   > {
-    return macrostep(snapshot, event, actorScope).microstates;
+    return macrostep(snapshot, event, actorScope, []).microstates;
   }
 
   public getTransitionData(
@@ -386,7 +387,8 @@ export class StateMachine<
         initEvent,
         actorScope,
         [assign(assignment)],
-        internalQueue
+        internalQueue,
+        undefined
       ) as SnapshotFrom<this>;
     }
 

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
@@ -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,
@@ -15,7 +15,8 @@ import type {
   ParameterizedObject,
   PropertyAssigner,
   ProvidedActor,
-  ActionFunction
+  ActionFunction,
+  BuiltinActionResolution
 } from '../types.ts';
 
 export interface AssignArgs<
@@ -39,7 +40,7 @@ function resolveAssign(
       | Assigner<any, any, any, any, any>
       | PropertyAssigner<any, any, any, any, any>;
   }
-) {
+): BuiltinActionResolution {
   if (!snapshot.context) {
     throw new Error(
       'Cannot assign to undefined `context`. Ensure that `context` is defined in the machine config.'
@@ -83,7 +84,9 @@ function resolveAssign(
             ...spawnedChildren
           }
         : snapshot.children
-    })
+    }),
+    undefined,
+    undefined
   ];
 }
 

packages/core/src/actions/cancel.ts

@@ -5,7 +5,8 @@ import {
   EventObject,
   MachineContext,
   ActionArgs,
-  ParameterizedObject
+  ParameterizedObject,
+  BuiltinActionResolution
 } from '../types.ts';
 
 type ResolvableSendId<
@@ -26,15 +27,15 @@ function resolveCancel(
   actionArgs: ActionArgs<any, any, any>,
   actionParams: ParameterizedObject['params'] | undefined,
   { sendId }: { sendId: ResolvableSendId<any, any, any, any> }
-) {
+): BuiltinActionResolution {
   const resolvedSendId =
     typeof sendId === 'function' ? sendId(actionArgs, actionParams) : sendId;
-  return [snapshot, resolvedSendId];
+  return [snapshot, { sendId: resolvedSendId }, undefined];
 }
 
-function executeCancel(actorScope: AnyActorScope, resolvedSendId: string) {
+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,
@@ -10,7 +10,8 @@ import {
   EventObject,
   MachineContext,
   ParameterizedObject,
-  SendExpr
+  SendExpr,
+  BuiltinActionResolution
 } from '../types.ts';
 
 function resolveEmit(
@@ -31,12 +32,12 @@ function resolveEmit(
           EventObject
         >;
   }
-) {
+): BuiltinActionResolution {
   const resolvedEvent =
     typeof eventOrExpr === 'function'
       ? eventOrExpr(args, actionParams)
       : eventOrExpr;
-  return [snapshot, { event: resolvedEvent }];
+  return [snapshot, { event: resolvedEvent }, undefined];
 }
 
 function executeEmit(

packages/core/src/actions/enqueueActions.ts

@@ -12,6 +12,7 @@ import {
   MachineContext,
   ParameterizedObject,
   ProvidedActor,
+  BuiltinActionResolution,
   UnifiedArg
 } from '../types.ts';
 import { assign } from './assign.ts';
@@ -130,7 +131,7 @@ function resolveEnqueueActions(
       EventObject
     >;
   }
-) {
+): BuiltinActionResolution {
   const actions: any[] = [];
   const enqueue: Parameters<typeof collect>[0]['enqueue'] = function enqueue(
     action