TanStack · ThiloAschebrock · Oct 26, 2025
diff --git a/.changeset/puny-melons-deny.md b/.changeset/puny-melons-deny.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/angular-query-experimental': minor
+---
+
+Ensure initial mutation pending state is emitted
diff --git a/packages/angular-query-experimental/src/__tests__/inject-mutation.test.ts b/packages/angular-query-experimental/src/__tests__/inject-mutation.test.ts
@@ -55,8 +55,6 @@ describe('injectMutation', () => {
       }))
     })
 
-    TestBed.tick()
-
     mutation.mutate(result)
     await vi.advanceTimersByTimeAsync(0)
 
@@ -389,11 +387,42 @@ describe('injectMutation', () => {
     expect(mutation2!.options.mutationKey).toEqual(['fake', 'updatedValue'])
   })
 
+  test('should have pending state when mutating in constructor', async () => {
+    @Component({
+      selector: 'app-fake',
+      template: `
+        <span>{{ mutation.isPending() ? 'pending' : 'not pending' }}</span>
+      `,
+    })
+    class FakeComponent {
+      mutation = injectMutation(() => ({
+        mutationKey: ['fake'],
+        mutationFn: () => sleep(10).then(() => 'fake'),
+      }))
+
+      constructor() {
+        this.mutation.mutate()
+      }
+    }
+
+    const fixture = TestBed.createComponent(FakeComponent)
+    const { debugElement } = fixture
+    const span = debugElement.query(By.css('span'))
+
+    await vi.advanceTimersByTimeAsync(0)
+    expect(span.nativeElement.textContent).toEqual('pending')
+
+    await vi.advanceTimersByTimeAsync(11)
+    fixture.detectChanges()
+
+    expect(span.nativeElement.textContent).toEqual('not pending')
+  })
+
   describe('throwOnError', () => {
     test('should evaluate throwOnError when mutation is expected to throw', async () => {
       const err = new Error('Expected mock error. All is well!')
       const boundaryFn = vi.fn()
-      const { mutate } = TestBed.runInInjectionContext(() => {
+      const { mutate, status, error } = TestBed.runInInjectionContext(() => {
         return injectMutation(() => ({
           mutationKey: ['fake'],
           mutationFn: () => {
@@ -403,14 +432,14 @@ describe('injectMutation', () => {
         }))
       })
 
-      TestBed.tick()
-
       mutate()
 
       await vi.advanceTimersByTimeAsync(0)
 
       expect(boundaryFn).toHaveBeenCalledTimes(1)
       expect(boundaryFn).toHaveBeenCalledWith(err)
+      expect(status()).toBe('error')
+      expect(error()).toBe(err)
     })
   })
 
@@ -533,21 +562,8 @@ describe('injectMutation', () => {
       // Start mutation
       mutation.mutate('retry-test')
 
-      // Synchronize pending effects for each retry attempt
-      TestBed.tick()
-      await Promise.resolve()
-      await vi.advanceTimersByTimeAsync(10)
-
-      TestBed.tick()
-      await Promise.resolve()
-      await vi.advanceTimersByTimeAsync(10)
-
-      TestBed.tick()
-
-      const stablePromise = app.whenStable()
-      await Promise.resolve()
-      await vi.advanceTimersByTimeAsync(10)
-      await stablePromise
+      await vi.advanceTimersByTimeAsync(30)
+      await app.whenStable()
 
       expect(mutation.isSuccess()).toBe(true)
       expect(mutation.data()).toBe('processed: retry-test')
@@ -590,14 +606,8 @@ describe('injectMutation', () => {
       mutation1.mutate('test1')
       mutation2.mutate('test2')
 
-      // Synchronize pending effects
-      TestBed.tick()
-
-      const stablePromise = app.whenStable()
-      // Flush microtasks to allow TanStack Query's scheduled notifications to process
-      await Promise.resolve()
       await vi.advanceTimersByTimeAsync(1)
-      await stablePromise
+      await app.whenStable()
 
       expect(mutation1.isSuccess()).toBe(true)
       expect(mutation1.data()).toBe('mutation1: test1')
@@ -642,14 +652,8 @@ describe('injectMutation', () => {
       // Start mutation
       mutation.mutate('test')
 
-      // Synchronize pending effects
-      TestBed.tick()
-
-      const stablePromise = app.whenStable()
-      // Flush microtasks to allow TanStack Query's scheduled notifications to process
-      await Promise.resolve()
       await vi.advanceTimersByTimeAsync(1)
-      await stablePromise
+      await app.whenStable()
 
       expect(onMutateCalled).toBe(true)
       expect(onSuccessCalled).toBe(true)
@@ -679,14 +683,8 @@ describe('injectMutation', () => {
       // Start mutation
       mutation.mutate('test')
 
-      // Synchronize pending effects
-      TestBed.tick()
-
-      const stablePromise = app.whenStable()
-      // Flush microtasks to allow TanStack Query's scheduled notifications to process
-      await Promise.resolve()
       await vi.advanceTimersByTimeAsync(1)
-      await stablePromise
+      await app.whenStable()
 
       // Synchronous mutations complete immediately
       expect(mutation.isSuccess()).toBe(true)

diff --git a/packages/angular-query-experimental/src/inject-mutation.ts b/packages/angular-query-experimental/src/inject-mutation.ts
@@ -1,9 +1,9 @@
 import {
+  DestroyRef,
   Injector,
   NgZone,
   assertInInjectionContext,
   computed,
-  effect,
   inject,
   signal,
   untracked,
@@ -17,8 +17,7 @@ import {
 } from '@tanstack/query-core'
 import { signalProxy } from './signal-proxy'
 import { PENDING_TASKS } from './pending-tasks-compat'
-import type { PendingTaskRef } from './pending-tasks-compat'
-import type { DefaultError, MutationObserverResult } from '@tanstack/query-core'
+import type { DefaultError } from '@tanstack/query-core'
 import type {
   CreateMutateFunction,
   CreateMutationOptions,
@@ -58,6 +57,7 @@ export function injectMutation<
 ): CreateMutationResult<TData, TError, TVariables, TOnMutateResult> {
   !options?.injector && assertInInjectionContext(injectMutation)
   const injector = options?.injector ?? inject(Injector)
+  const destroyRef = injector.get(DestroyRef)
   const ngZone = injector.get(NgZone)
   const pendingTasks = injector.get(PENDING_TASKS)
   const queryClient = injector.get(QueryClient)
@@ -78,7 +78,15 @@ export function injectMutation<
     > | null = null
 
     return computed(() => {
-      return (instance ||= new MutationObserver(queryClient, optionsSignal()))
+      const observerOptions = optionsSignal()
+      return untracked(() => {
+        if (instance) {
+          instance.setOptions(observerOptions)
+        } else {
+          instance = new MutationObserver(queryClient, observerOptions)
+        }
+        return instance
+      })
     })
   })()
 
@@ -87,97 +95,75 @@ export function injectMutation<
   >(() => {
     const observer = observerSignal()
     return (variables, mutateOptions) => {
-      observer.mutate(variables, mutateOptions).catch(noop)
+      void observer.mutate(variables, mutateOptions).catch(noop)
     }
   })
 
-  /**
-   * Computed signal that gets result from mutation cache based on passed options
-   */
-  const resultFromInitialOptionsSignal = computed(() => {
-    const observer = observerSignal()
-    return observer.getCurrentResult()
-  })
+  let cleanup: () => void = noop
 
   /**
-   * Signal that contains result set by subscriber
+   * Returning a writable signal from a computed is similar to `linkedSignal`,
+   * but compatible with Angular < 19
+   *
+   * Compared to `linkedSignal`, this pattern requires extra parentheses:
+   * - Accessing value: `result()()`
+   * - Setting value: `result().set(newValue)`
    */
-  const resultFromSubscriberSignal = signal<MutationObserverResult<
-    TData,
-    TError,
-    TVariables,
-    TOnMutateResult
-  > | null>(null)
-
-  effect(
-    () => {
-      const observer = observerSignal()
-      const observerOptions = optionsSignal()
+  const linkedResultSignal = computed(() => {
+    const observer = observerSignal()
 
-      untracked(() => {
-        observer.setOptions(observerOptions)
-      })
-    },
-    {
-      injector,
-    },
-  )
-
-  effect(
-    (onCleanup) => {
+    return untracked(() => {
       // observer.trackResult is not used as this optimization is not needed for Angular
-      const observer = observerSignal()
-      let pendingTaskRef: PendingTaskRef | null = null
-
-      untracked(() => {
-        const unsubscribe = ngZone.runOutsideAngular(() =>
-          observer.subscribe(
-            notifyManager.batchCalls((state) => {
-              ngZone.run(() => {
-                // Track pending task when mutation is pending
-                if (state.isPending && !pendingTaskRef) {
-                  pendingTaskRef = pendingTasks.add()
-                }
-
-                // Clear pending task when mutation is no longer pending
-                if (!state.isPending && pendingTaskRef) {
-                  pendingTaskRef()
-                  pendingTaskRef = null
-                }
-
-                if (
-                  state.isError &&
-                  shouldThrowError(observer.options.throwOnError, [state.error])
-                ) {
-                  ngZone.onError.emit(state.error)
-                  throw state.error
-                }
-
-                resultFromSubscriberSignal.set(state)
-              })
-            }),
-          ),
-        )
-        onCleanup(() => {
-          // Clean up any pending task on destroy
-          if (pendingTaskRef) {
-            pendingTaskRef()
-            pendingTaskRef = null
-          }
-          unsubscribe()
-        })
-      })
-    },
-    {
-      injector,
-    },
-  )
+      const currentResult = observer.getCurrentResult()
+      const result = signal(currentResult)
+
+      cleanup()
+      let pendingTaskRef = currentResult.isPending ? pendingTasks.add() : null
+
+      const unsubscribe = ngZone.runOutsideAngular(() =>
+        observer.subscribe(
+          notifyManager.batchCalls((state) => {
+            ngZone.run(() => {
+              result.set(state)
+
+              // Track pending task when mutation is pending
+              if (state.isPending && !pendingTaskRef) {
+                pendingTaskRef = pendingTasks.add()
+              }
+
+              // Clear pending task when mutation is no longer pending
+              if (!state.isPending && pendingTaskRef) {
+                pendingTaskRef()
+                pendingTaskRef = null
+              }
+
+              if (
+                state.isError &&
+                shouldThrowError(observer.options.throwOnError, [state.error])
+              ) {
+                ngZone.onError.emit(state.error)
+                throw state.error
+              }
+            })
+          }),
+        ),
+      )
+
+      cleanup = () => {
+        // Clean up any pending task on destroy
+        if (pendingTaskRef) {
+          pendingTaskRef()
+          pendingTaskRef = null
+        }
+        unsubscribe()
+      }
+
+      return result
+    })
+  })
 
   const resultSignal = computed(() => {
-    const resultFromSubscriber = resultFromSubscriberSignal()
-    const resultFromInitialOptions = resultFromInitialOptionsSignal()
-
-    const result = resultFromSubscriber ?? resultFromInitialOptions
+    const result = linkedResultSignal()()
 
     return {
       ...result,
@@ -186,6 +172,8 @@ export function injectMutation<
     }
   })
 
+  destroyRef.onDestroy(() => cleanup())
+
   return signalProxy(resultSignal) as CreateMutationResult<
     TData,
     TError,