Fix persisting unresolved promises (#3959)

* Fix persisting unresolved promises * Changeset * Avoid mutations of the internal state in all actor types (#3970) --------- Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>
statelyai · Apr 19, 2023 · ead2872 · ead2872
1 parent 423c5ab
commit ead2872
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diff --git a/.changeset/large-cooks-taste.md b/.changeset/large-cooks-taste.md
@@ -0,0 +1,5 @@
+---
+'xstate': patch
+---
+
+Unresolved promises will now be properly persisted. The current behavior is to restart a promise that is unresolved.
diff --git a/packages/core/src/actors/callback.ts b/packages/core/src/actors/callback.ts
@@ -34,7 +34,7 @@ export function fromCallback<TEvent extends EventObject>(
       if (_event.name === startSignalType) {
         const sender = (eventForParent: AnyEventObject) => {
           if (state.canceled) {
-            return state;
+            return;
           }
 
           self._parent?.send(toSCXMLEvent(eventForParent, { origin: self }));

diff --git a/packages/core/src/actors/observable.ts b/packages/core/src/actors/observable.ts
@@ -9,8 +9,7 @@ import { stopSignalType } from '../actors';
 
 export interface ObservableInternalState<T> {
   subscription: Subscription | undefined;
-  canceled: boolean;
-  status: 'active' | 'done' | 'error';
+  status: 'active' | 'done' | 'error' | 'canceled';
   data: T | undefined;
   input?: any;
 }
@@ -43,13 +42,12 @@ export function fromObservable<T, TEvent extends EventObject>(
     transition: (state, event, { self, id, defer }) => {
       const _event = toSCXMLEvent(event);
 
-      if (state.canceled) {
+      if (state.status !== 'active') {
         return state;
       }
 
       switch (_event.name) {
         case nextEventType:
-          state.data = event.data.data;
           // match the exact timing of events sent by machines
           // send actions are not executed immediately
           defer(() => {
@@ -63,29 +61,40 @@ export function fromObservable<T, TEvent extends EventObject>(
               )
             );
           });
-          return state;
+          return {
+            ...state,
+            data: event.data.data
+          };
         case errorEventType:
-          state.status = 'error';
-          delete state.input;
-          state.data = _event.data.data;
-          return state;
+          return {
+            ...state,
+            status: 'error',
+            input: undefined,
+            data: _event.data.data,
+            subscription: undefined
+          };
         case completeEventType:
-          state.status = 'done';
-          delete state.input;
-          return state;
+          return {
+            ...state,
+            status: 'done',
+            input: undefined,
+            subscription: undefined
+          };
         case stopSignalType:
-          state.canceled = true;
-          delete state.input;
           state.subscription!.unsubscribe();
-          return state;
+          return {
+            ...state,
+            status: 'canceled',
+            input: undefined,
+            subscription: undefined
+          };
         default:
           return state;
       }
     },
     getInitialState: (_, input) => {
       return {
         subscription: undefined,
-        canceled: false,
         status: 'active',
         data: undefined,
         input
@@ -109,8 +118,7 @@ export function fromObservable<T, TEvent extends EventObject>(
       });
     },
     getSnapshot: (state) => state.data,
-    getPersistedState: ({ canceled, status, data, input }) => ({
-      canceled,
+    getPersistedState: ({ status, data, input }) => ({
       status,
       data,
       input
@@ -150,33 +158,41 @@ export function fromEventObservable<T extends EventObject>(
     transition: (state, event) => {
       const _event = toSCXMLEvent(event);
 
-      if (state.canceled) {
+      if (state.status !== 'active') {
         return state;
       }
 
       switch (_event.name) {
         case errorEventType:
-          state.status = 'error';
-          delete state.input;
-          state.data = _event.data.data;
-          return state;
+          return {
+            ...state,
+            status: 'error',
+            input: undefined,
+            data: _event.data.data,
+            subscription: undefined
+          };
         case completeEventType:
-          state.status = 'done';
-          delete state.input;
-          return state;
+          return {
+            ...state,
+            status: 'done',
+            input: undefined,
+            subscription: undefined
+          };
         case stopSignalType:
-          state.canceled = true;
-          delete state.input;
           state.subscription!.unsubscribe();
-          return state;
+          return {
+            ...state,
+            status: 'canceled',
+            input: undefined,
+            subscription: undefined
+          };
         default:
           return state;
       }
     },
     getInitialState: () => {
       return {
         subscription: undefined,
-        canceled: false,
         status: 'active',
         data: undefined
       };
@@ -200,8 +216,7 @@ export function fromEventObservable<T extends EventObject>(
       });
     },
     getSnapshot: (_) => undefined,
-    getPersistedState: ({ canceled, status, data, input }) => ({
-      canceled,
+    getPersistedState: ({ status, data, input }) => ({
       status,
       data,
       input

diff --git a/packages/core/src/actors/promise.ts b/packages/core/src/actors/promise.ts
@@ -3,8 +3,7 @@ import { toSCXMLEvent } from '../utils';
 import { stopSignalType } from '../actors';
 
 export interface PromiseInternalState<T> {
-  status: 'active' | 'error' | 'done';
-  canceled: boolean;
+  status: 'active' | 'error' | 'done' | 'canceled';
   data: T | undefined;
   input?: any;
 }
@@ -33,27 +32,33 @@ export function fromPromise<T>(
     transition: (state, event) => {
       const _event = toSCXMLEvent(event);
 
-      if (state.canceled) {
+      if (state.status !== 'active') {
         return state;
       }
 
       const eventObject = _event.data;
 
       switch (_event.name) {
         case resolveEventType:
-          state.status = 'done';
-          state.data = eventObject.data;
-          delete state.input;
-          return state;
+          return {
+            ...state,
+            status: 'done',
+            data: eventObject.data,
+            input: undefined
+          };
         case rejectEventType:
-          state.status = 'error';
-          state.data = eventObject.data;
-          delete state.input;
-          return state;
+          return {
+            ...state,
+            status: 'error',
+            data: eventObject.data,
+            input: undefined
+          };
         case stopSignalType:
-          state.canceled = true;
-          delete state.input;
-          return state;
+          return {
+            ...state,
+            status: 'canceled',
+            input: undefined
+          };
         default:
           return state;
       }
@@ -80,7 +85,6 @@ export function fromPromise<T>(
     },
     getInitialState: (_, input) => {
       return {
-        canceled: false,
         status: 'active',
         data: undefined,
         input

diff --git a/packages/core/test/behaviors.test.ts b/packages/core/test/behaviors.test.ts
@@ -86,7 +86,31 @@ describe('promise behavior (fromPromise)', () => {
     expect(called).toBe(false);
   });
 
-  it('should persist a promise', (done) => {
+  it('should persist an unresolved promise', (done) => {
+    const promiseBehavior = fromPromise(
+      () =>
+        new Promise<number>((res) => {
+          setTimeout(() => res(42), 10);
+        })
+    );
+
+    const actor = interpret(promiseBehavior);
+    actor.start();
+
+    const resolvedPersistedState = actor.getPersistedState();
+    actor.stop();
+
+    const restoredActor = interpret(promiseBehavior, {
+      state: resolvedPersistedState
+    }).start();
+
+    setTimeout(() => {
+      expect(restoredActor.getSnapshot()).toBe(42);
+      done();
+    }, 20);
+  });
+
+  it('should persist a resolved promise', (done) => {
     const promiseBehavior = fromPromise(
       () =>
         new Promise<number>((res) => {
@@ -350,7 +374,7 @@ describe('machine behavior', () => {
 
     expect(persistedState.children.a.state).toEqual(
       expect.objectContaining({
-        canceled: false,
+        status: 'done',
         data: 42
       })
     );