Merge pull request #2632 from statelyai/davidkpiano/model-actions-fix

[core] Allow any action if action creators are not specified in model
statelyai · Sep 14, 2021 · cda1b9e · cda1b9e
2 parents ef70ce9 + f8cf5df
commit cda1b9e
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diff --git a/.changeset/slow-timers-nail.md b/.changeset/slow-timers-nail.md
@@ -0,0 +1,20 @@
+---
+'xstate': patch
+---
+
+A regression was fixed where actions were being typed as `never` if events were specified in `createModel(...)` but not actions:
+
+```ts
+const model = createModel(
+  {},
+  {
+    events: {}
+  }
+);
+
+model.createMachine({
+  // These actions will cause TS to not compile
+  entry: 'someAction',
+  exit: { type: 'someObjectAction' }
+});
+```
diff --git a/packages/core/src/model.ts b/packages/core/src/model.ts
@@ -22,9 +22,11 @@ export function createModel<
   TComputedEvent = 'events' extends keyof TFinalModelCreators
     ? UnionFromCreatorsReturnTypes<TFinalModelCreators['events']>
     : never,
-  TComputedAction = 'actions' extends keyof TFinalModelCreators
-    ? UnionFromCreatorsReturnTypes<TFinalModelCreators['actions']>
-    : never
+  TComputedAction = 'actions' extends keyof TModelCreators
+    ? 'actions' extends keyof TFinalModelCreators
+      ? UnionFromCreatorsReturnTypes<TFinalModelCreators['actions']>
+      : any
+    : any
 >(
   initialContext: TContext,
   creators: TModelCreators

diff --git a/packages/core/test/model.test.ts b/packages/core/test/model.test.ts
@@ -436,7 +436,14 @@ describe('createModel', () => {
   });
 
   it('should typecheck `createMachine` for model without creators', () => {
-    const toggleModel = createModel({ count: 0 });
+    const toggleModel = createModel(
+      { count: 0 },
+      {
+        events: {
+          TOGGLE: () => ({})
+        }
+      }
+    );
 
     toggleModel.createMachine({
       id: 'machine',
@@ -519,6 +526,24 @@ describe('createModel', () => {
     });
   });
 
+  it('should allow any action if actions are not specified', () => {
+    const model = createModel(
+      {},
+      {
+        events: {}
+      }
+    );
+
+    model.createMachine({
+      entry: 'someAction',
+      exit: { type: 'someObjectAction' },
+      on: {
+        // @ts-expect-error
+        UNEXPECTED_EVENT: {}
+      }
+    });
+  });
+
   it('should keep the context type on the state after using `state.matches`', () => {
     const model = createModel<{ count: number }, { type: 'INC' }>({ count: 0 });