From 302aee0df9bf6ba1d85b0c82eedbe32c453d2428 Mon Sep 17 00:00:00 2001
From: riccardoperra <riccardo.perra@icloud.com>
Date: Mon, 4 Mar 2024 00:10:50 +0100
Subject: [PATCH] feat(angular-query): lazy signal initializer test

---
 .../lazy-signal-initializer.test.ts           | 136 ++++++++++++++++++
 .../lazy-signal-initializer.ts                |  23 +--
 2 files changed, 148 insertions(+), 11 deletions(-)
 create mode 100644 packages/angular-query-experimental/src/__tests__/util/lazy-signal-initializer/lazy-signal-initializer.test.ts

diff --git a/packages/angular-query-experimental/src/__tests__/util/lazy-signal-initializer/lazy-signal-initializer.test.ts b/packages/angular-query-experimental/src/__tests__/util/lazy-signal-initializer/lazy-signal-initializer.test.ts
new file mode 100644
index 0000000000..afdd71e3f4
--- /dev/null
+++ b/packages/angular-query-experimental/src/__tests__/util/lazy-signal-initializer/lazy-signal-initializer.test.ts
@@ -0,0 +1,136 @@
+import { describe, expect, test } from 'vitest'
+import {
+  Component,
+  type Signal,
+  type WritableSignal,
+  effect,
+  input,
+  signal,
+} from '@angular/core'
+import { TestBed } from '@angular/core/testing'
+import { lazySignalInitializer } from '../../../util/lazy-signal-initializer/lazy-signal-initializer'
+import { setFixtureSignalInputs } from '../../test-utils'
+
+async function flushQueue() {
+  await new Promise(setImmediate)
+}
+
+describe('lazySignalInitializer', () => {
+  test('should init lazily in next tick when not accessing manually', async () => {
+    const mockFn = vi.fn()
+
+    TestBed.runInInjectionContext(() => {
+      lazySignalInitializer(() => {
+        mockFn()
+        return signal(true)
+      })
+    })
+
+    expect(mockFn).not.toHaveBeenCalled()
+
+    await new Promise(setImmediate)
+
+    expect(mockFn).toHaveBeenCalled()
+  })
+
+  test('should init eagerly accessing manually', async () => {
+    const mockFn = vi.fn()
+
+    TestBed.runInInjectionContext(() => {
+      const lazySignal = lazySignalInitializer(() => {
+        mockFn()
+        return signal(true)
+      })
+
+      lazySignal()
+    })
+
+    expect(mockFn).toHaveBeenCalled()
+  })
+
+  test('should init lazily and only once', async () => {
+    const initCallFn = vi.fn()
+    const registerEffectValue = vi.fn<[number]>()
+
+    let value!: Signal<number>
+    const outerSignal = signal(0)
+    let innerSignal!: WritableSignal<number>
+
+    TestBed.runInInjectionContext(() => {
+      value = lazySignalInitializer(() => {
+        initCallFn()
+        innerSignal = signal(0)
+
+        void outerSignal()
+
+        return innerSignal
+      })
+
+      effect(() => registerEffectValue(value()))
+    })
+
+    expect(initCallFn).toHaveBeenCalledTimes(0)
+    expect(outerSignal).toBeDefined()
+    expect(innerSignal).not.toBeDefined()
+
+    await flushQueue()
+
+    expect(outerSignal).toBeDefined()
+    expect(innerSignal).toBeDefined()
+
+    expect(initCallFn).toHaveBeenCalledTimes(1)
+
+    innerSignal.set(1)
+    await flushQueue()
+    outerSignal.set(2)
+    await flushQueue()
+
+    expect(initCallFn).toHaveBeenCalledTimes(1)
+    expect(registerEffectValue).toHaveBeenCalledTimes(2)
+  })
+
+  test('should init lazily', async () => {
+    @Component({
+      standalone: true,
+      template: `{{ subscribed }}`,
+    })
+    class Test {
+      subscribed = false
+
+      lazySignal = lazySignalInitializer(() => {
+        this.subscribed = true
+        return signal('value')
+      })
+    }
+
+    const fixture = TestBed.createComponent(Test)
+    const { debugElement } = fixture
+    fixture.detectChanges()
+
+    expect(debugElement.nativeElement.textContent).toBe('false')
+
+    await new Promise(setImmediate)
+
+    fixture.detectChanges()
+
+    expect(debugElement.nativeElement.textContent).toBe('true')
+  })
+
+  test('should support required signal input', () => {
+    @Component({
+      standalone: true,
+      template: `{{ subscribed }}`,
+    })
+    class Test {
+      readonly title = input.required<string>()
+      subscribed = false
+
+      lazySignal = lazySignalInitializer(() => {
+        return signal(this.title())
+      })
+    }
+
+    const fixture = TestBed.createComponent(Test)
+    setFixtureSignalInputs(fixture, { title: 'newValue' })
+  })
+})
diff --git a/packages/angular-query-experimental/src/util/lazy-signal-initializer/lazy-signal-initializer.ts b/packages/angular-query-experimental/src/util/lazy-signal-initializer/lazy-signal-initializer.ts
index 52998030e8..eb33083aab 100644
--- a/packages/angular-query-experimental/src/util/lazy-signal-initializer/lazy-signal-initializer.ts
+++ b/packages/angular-query-experimental/src/util/lazy-signal-initializer/lazy-signal-initializer.ts
@@ -1,4 +1,10 @@
-import { Injector, type Signal, computed, inject } from '@angular/core'
+import {
+  Injector,
+  type Signal,
+  computed,
+  inject,
+  untracked,
+} from '@angular/core'
 
 type SignalInitializerFn<T> = (injector: Injector) => Signal<T>
 
@@ -9,19 +15,14 @@ export function lazySignalInitializer<T>(
 
   let source: Signal<T> | null = null
 
-  const initializeObject = () => {
+  const unwrapSignal = () => {
     if (!source) {
-      source = initializerFn(injector)
+      source = untracked(() => initializerFn(injector))
     }
-    return source
+    return source()
   }
 
-  queueMicrotask(() => initializeObject())
+  queueMicrotask(() => unwrapSignal())
 
-  return computed(() => {
-    if (!source) {
-      source = initializeObject()
-    }
-    return source()
-  })
+  return computed(unwrapSignal)
 }