fix(query-core): use !== undefined for timer ID checks to handle falsy 0

.changeset/seven-facts-unite.md

@@ -0,0 +1,6 @@
+---
+'@tanstack/query-core': patch
+---
+
+fix: use !== undefined instead of truthy check for timer IDs to correctly handle falsy value 0 in clearGcTimeout,  
+

packages/query-core/src/__tests__/queryObserver.test.tsx

@@ -10,6 +10,7 @@ import {
 } from 'vitest'
 import { queryKey, sleep } from '@tanstack/query-test-utils'
 import { QueryClient, QueryObserver, focusManager } from '..'
+import { defaultTimeoutProvider, timeoutManager } from '../timeoutManager'
 import type { QueryObserverResult } from '..'
 
 describe('queryObserver', () => {
@@ -1626,4 +1627,60 @@ describe('queryObserver', () => {
       unsubscribe2()
     })
   })
+
+  describe('falsy timer ID (0) handling', () => {
+    test('should call clearTimeout when stale timer ID is 0', async () => {
+      const provider = {
+        setTimeout: vi.fn(() => 0),
+        clearTimeout: vi.fn(),
+        setInterval: vi.fn(() => 0),
+        clearInterval: vi.fn(),
+      }
+      timeoutManager.setTimeoutProvider(provider)
+
+      const key = queryKey()
+      const observer = new QueryObserver(queryClient, {
+        queryKey: key,
+        queryFn: () => 'data',
+        staleTime: 100,
+      })
+
+      const unsubscribe = observer.subscribe(() => undefined)
+      await vi.advanceTimersByTimeAsync(0)
+
+      // setOptions triggers #clearStaleTimeout → must call clearTimeout(0)
+      observer.setOptions({ queryKey: key, queryFn: () => 'data', staleTime: 200 })
+
+      expect(provider.clearTimeout).toHaveBeenCalledWith(0)
+
+      unsubscribe()
+      timeoutManager.setTimeoutProvider(defaultTimeoutProvider)
+    })
+
+    test('should call clearInterval when refetch interval timer ID is 0', async () => {
+      const provider = {
+        setTimeout: vi.fn(() => 0),
+        clearTimeout: vi.fn(),
+        setInterval: vi.fn(() => 0),
+        clearInterval: vi.fn(),
+      }
+      timeoutManager.setTimeoutProvider(provider)
+
+      const key = queryKey()
+      const observer = new QueryObserver(queryClient, {
+        queryKey: key,
+        queryFn: () => 'data',
+        refetchInterval: 100,
+      })
+
+      const unsubscribe = observer.subscribe(() => undefined)
+      await vi.advanceTimersByTimeAsync(0)
+
+      unsubscribe() // destroy → #clearRefetchInterval → must call clearInterval(0)
+
+      expect(provider.clearInterval).toHaveBeenCalledWith(0)
+
+      timeoutManager.setTimeoutProvider(defaultTimeoutProvider)
+    })
+  })
 })

packages/query-core/src/__tests__/removable.test.tsx

@@ -0,0 +1,51 @@
+import { afterEach, beforeEach, describe, expect, test, vi } from 'vitest'
+import { queryKey } from '@tanstack/query-test-utils'
+import { QueryClient, QueryObserver } from '..'
+import { defaultTimeoutProvider, timeoutManager } from '../timeoutManager'
+
+describe('removable', () => {
+  let queryClient: QueryClient
+
+  beforeEach(() => {
+    vi.useFakeTimers()
+    queryClient = new QueryClient()
+    queryClient.mount()
+  })
+
+  afterEach(() => {
+    queryClient.clear()
+    vi.useRealTimers()
+    timeoutManager.setTimeoutProvider(defaultTimeoutProvider)
+  })
+
+  describe('falsy timer ID (0) handling', () => {
+    test('should call clearTimeout for gcTimeout when timer ID is 0', async () => {
+      const provider = {
+        setTimeout: vi.fn(() => 0),
+        clearTimeout: vi.fn(),
+        setInterval: vi.fn(() => 0),
+        clearInterval: vi.fn(),
+      }
+      timeoutManager.setTimeoutProvider(provider)
+
+      const key = queryKey()
+      const observer = new QueryObserver(queryClient, {
+        queryKey: key,
+        queryFn: () => 'data',
+        gcTime: 100,
+      })
+
+      // Subscribe then unsubscribe: no observers left → scheduleGc() sets #gcTimeout = 0
+      const unsubscribe = observer.subscribe(() => undefined)
+      await vi.advanceTimersByTimeAsync(0)
+      unsubscribe()
+
+      // Subscribe again: addObserver calls clearGcTimeout() → must call clearTimeout(0)
+      const unsubscribe2 = observer.subscribe(() => undefined)
+
+      expect(provider.clearTimeout).toHaveBeenCalledWith(0)
+
+      unsubscribe2()
+    })
+  })
+})

packages/query-core/src/queryObserver.ts

@@ -417,14 +417,14 @@ export class QueryObserver<
   }
 
   #clearStaleTimeout(): void {
-    if (this.#staleTimeoutId) {
+    if (this.#staleTimeoutId !== undefined) {
       timeoutManager.clearTimeout(this.#staleTimeoutId)
       this.#staleTimeoutId = undefined
     }
   }
 
   #clearRefetchInterval(): void {
-    if (this.#refetchIntervalId) {
+    if (this.#refetchIntervalId !== undefined) {
       timeoutManager.clearInterval(this.#refetchIntervalId)
       this.#refetchIntervalId = undefined
     }

packages/query-core/src/removable.ts

@@ -30,7 +30,7 @@ export abstract class Removable {
   }
 
   protected clearGcTimeout() {
-    if (this.#gcTimeout) {
+    if (this.#gcTimeout !== undefined) {
       timeoutManager.clearTimeout(this.#gcTimeout)
       this.#gcTimeout = undefined
     }