feat(types): Lazy, LazyPromise, LazyNullablePromise

src/decorators/memo.decorator.test.ts

@@ -54,7 +54,7 @@ test('MEMO_DROP_CACHE', () => {
   // second call
   a.a(2, 3)
 
-  expect(a.func).toBeCalledTimes(2)
+  expect(a.func).toHaveBeenCalledTimes(2)
 })
 
 test('memo unsupported', () => {

src/decorators/memoSimple.decorator.test.ts

@@ -49,7 +49,7 @@ test('MEMO_DROP_CACHE', () => {
   // second call
   a.a(2, 3)
 
-  expect(a.func).toBeCalledTimes(2)
+  expect(a.func).toHaveBeenCalledTimes(2)
 })
 
 test('memo unsupported', () => {

src/define.test.ts

@@ -1,21 +1,23 @@
+import { expectTypeOf } from 'expect-type'
 import {
   _defineLazyProperty,
   _defineLazyProps,
   _defineProperty,
   _defineProps,
   _lazyValue,
 } from './define'
-import { AnyObject } from './types'
+import { AnyObject, Lazy } from './types'
 
 test('_lazyValue', () => {
   const fn = jest.fn(() => 42)
 
   const value = _lazyValue(fn)
+  expectTypeOf(value).toEqualTypeOf<Lazy<number>>()
   expect(value()).toBe(42)
   expect(value()).toBe(42)
   expect(value()).toBe(42)
 
-  expect(fn).toBeCalledTimes(1)
+  expect(fn).toHaveBeenCalledTimes(1)
 })
 
 interface Obj {
@@ -33,7 +35,7 @@ test('_defineLazyProperty', () => {
   expect(obj.v).toBe(42)
   expect(obj.v).toBe(42)
 
-  expect(fn).toBeCalledTimes(1)
+  expect(fn).toHaveBeenCalledTimes(1)
 
   // Another way to declare an object:
 
@@ -60,12 +62,12 @@ test('_defineLazyProps', () => {
   expect(obj.v1).toBe(42)
   expect(obj.v1).toBe(42)
   expect(obj.v1).toBe(42)
-  expect(fn1).toBeCalledTimes(1)
+  expect(fn1).toHaveBeenCalledTimes(1)
 
   expect(obj.v2).toBe(48)
   expect(obj.v2).toBe(48)
   expect(obj.v2).toBe(48)
-  expect(fn2).toBeCalledTimes(1)
+  expect(fn2).toHaveBeenCalledTimes(1)
 })
 
 test('_defineProperty', () => {

src/define.ts

@@ -1,5 +1,5 @@
 import { _mapObject, _mapValues } from './object/object.util'
-import type { AnyFunction, AnyObject } from './types'
+import type { AnyFunction, AnyObject, Lazy } from './types'
 import { SKIP } from './types'
 
 /**
@@ -11,7 +11,7 @@ import { SKIP } from './types'
  *
  * Based on: https://github.com/sindresorhus/lazy-value
  */
-export function _lazyValue<T extends AnyFunction>(fn: T): T {
+export function _lazyValue<T>(fn: () => T): Lazy<T> {
   let isCalled = false
   let result: any
 

src/http/fetcher.test.ts

@@ -111,7 +111,7 @@ test('should not mutate console', () => {
   // So, it'll be called 0 times
   // Here we're expecting that it's called 1 time
   console.log('yo')
-  expect(consoleSpy).toBeCalledTimes(1)
+  expect(consoleSpy).toHaveBeenCalledTimes(1)
 })
 
 test('mocking fetch', async () => {

src/types.ts

@@ -90,6 +90,18 @@ export type AnyAsyncFunction<T = any> = (...args: any[]) => Promise<T>
 export type AsyncFunction<T = any> = () => Promise<T>
 export type AnyPromisableFunction<T = any> = (...args: any[]) => Promisable<T>
 export type PromisableFunction<T = any> = () => Promisable<T>
+/**
+ * A function that lazily calculates something.
+ */
+export type Lazy<T> = () => T
+/**
+ * A function that lazily calculates something async (returns a Promise).
+ */
+export type LazyPromise<T> = () => Promise<T>
+/**
+ * A function that lazily calculates something async, that can return null.
+ */
+export type LazyNullablePromise<T> = () => Promise<T | null>
 
 /**
  * Symbol to indicate END of Sequence.