Error on incompatible state value when resolving state (#4290)

* Handle incompatible state value * Changeset * Fix * Update packages/core/test/rehydration.test.ts Co-authored-by: Mateusz Burzyński <[email protected]> * Update .changeset/olive-sheep-fetch.md Co-authored-by: Mateusz Burzyński <[email protected]> * Update packages/core/test/rehydration.test.ts Co-authored-by: Mateusz Burzyński <[email protected]> --------- Co-authored-by: Mateusz Burzyński <[email protected]>
statelyai · Feb 14, 2024 · 7a8796f · 7a8796f
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diff --git a/.changeset/olive-sheep-fetch.md b/.changeset/olive-sheep-fetch.md
@@ -0,0 +1,5 @@
+---
+'xstate': minor
+---
+
+An error will now be thrown if an incompatible state value is passed to `machine.resolveState({ value })`.
diff --git a/examples/todomvc-react/readme.md b/examples/todomvc-react/readme.md
@@ -17,10 +17,10 @@ You may run the example locally with:
     pnpm run dev
 ```
 
-__OR__
+**OR**
 
 [Open in CodeSandbox](https://codesandbox.io/p/sandbox/github/statelyai/xstate/tree/main/examples/todomvc-react)
 
-__OR__
+**OR**
 
 [![Open in StackBlitz](https://developer.stackblitz.com/img/open_in_stackblitz.svg)](https://stackblitz.com/github/statelyai/xstate/tree/main/examples/todomvc-react)
diff --git a/packages/core/src/stateUtils.ts b/packages/core/src/stateUtils.ts
@@ -626,7 +626,13 @@ export function getStateNodes<
   TEvent extends EventObject
 >(stateNode: AnyStateNode, stateValue: StateValue): Array<AnyStateNode> {
   if (typeof stateValue === 'string') {
-    return [stateNode, stateNode.states[stateValue]];
+    const childStateNode = stateNode.states[stateValue];
+    if (!childStateNode) {
+      throw new Error(
+        `State '${stateValue}' does not exist on '${stateNode.id}'`
+      );
+    }
+    return [stateNode, childStateNode];
   }
 
   const childStateKeys = Object.keys(stateValue);

diff --git a/packages/core/test/rehydration.test.ts b/packages/core/test/rehydration.test.ts
@@ -123,6 +123,37 @@ describe('rehydration', () => {
 
       expect(actual).toEqual([]);
     });
+
+    it('should error on incompatible state value (shallow)', () => {
+      const machine = createMachine({
+        initial: 'valid',
+        states: {
+          valid: {}
+        }
+      });
+
+      expect(() => {
+        machine.resolveState({ value: 'invalid' });
+      }).toThrowError(/invalid/);
+    });
+
+    it('should error on incompatible state value (deep)', () => {
+      const machine = createMachine({
+        initial: 'parent',
+        states: {
+          parent: {
+            initial: 'valid',
+            states: {
+              valid: {}
+            }
+          }
+        }
+      });
+
+      expect(() => {
+        machine.resolveState({ value: { parent: 'invalid' } });
+      }).toThrowError(/invalid/);
+    });
   });
 
   it('should not replay actions when starting from a persisted state', () => {