fix(core): do not update mutations if key has changed (#6889)

* fix(core): do not update mutations if key has changed

* chore: remove .only test

packages/query-core/src/mutationObserver.ts

@@ -66,14 +66,15 @@ export class MutationObserver<
         observer: this,
       })
     }
-    this.#currentMutation?.setOptions(this.options)
 
     if (
       prevOptions?.mutationKey &&
       this.options.mutationKey &&
       hashKey(prevOptions.mutationKey) !== hashKey(this.options.mutationKey)
     ) {
       this.reset()
+    } else {
+      this.#currentMutation?.setOptions(this.options)
     }
   }
 

packages/query-core/src/tests/mutationObserver.test.tsx

@@ -126,4 +126,47 @@ describe('mutationObserver', () => {
 
     unsubscribe()
   })
+
+  test('changing mutation keys should not affect already existing mutations', async () => {
+    const key = queryKey()
+    const mutationObserver = new MutationObserver(queryClient, {
+      mutationKey: [...key, '1'],
+      mutationFn: async (text: string) => {
+        await sleep(5)
+        return text
+      },
+    })
+
+    const subscriptionHandler = vi.fn()
+
+    const unsubscribe = mutationObserver.subscribe(subscriptionHandler)
+
+    await mutationObserver.mutate('input')
+
+    expect(
+      queryClient.getMutationCache().find({ mutationKey: [...key, '1'] }),
+    ).toMatchObject({
+      options: { mutationKey: [...key, '1'] },
+      state: {
+        status: 'success',
+        data: 'input',
+      },
+    })
+
+    mutationObserver.setOptions({
+      mutationKey: [...key, '2'],
+    })
+
+    expect(
+      queryClient.getMutationCache().find({ mutationKey: [...key, '1'] }),
+    ).toMatchObject({
+      options: { mutationKey: [...key, '1'] },
+      state: {
+        status: 'success',
+        data: 'input',
+      },
+    })
+
+    unsubscribe()
+  })
 })