test: add unit test for runPendingImmediatesAfterCurrentTask

Author: lubieowoce

packages/next/src/server/app-render/fast-set-immediate.external.test.ts

@@ -0,0 +1,106 @@
+import { createPromiseWithResolvers } from '../../shared/lib/promise-with-resolvers'
+import {
+  install,
+  runPendingImmediatesAfterCurrentTask,
+} from './fast-set-immediate.external'
+
+install()
+
+it('runs immediates after each task', async () => {
+  const logs: string[] = []
+
+  const log = (...args: any[]) => {
+    const { inspect } = require('node:util') as typeof import('node:util')
+
+    let logLine = args
+      .map((arg) =>
+        typeof arg === 'string' ? arg : inspect(arg, { colors: true })
+      )
+      .join(' ')
+
+    logs.push(logLine)
+    process.stdout.write(logLine + '\n')
+  }
+
+  const done = createPromiseWithResolvers<void>()
+
+  setTimeout(() => {
+    runPendingImmediatesAfterCurrentTask()
+
+    log('timeout 1')
+    setImmediate(() => {
+      log('timeout 1 -> immediate 1')
+      process.nextTick(() => {
+        log('timeout 1 -> immediate 1 -> nextTick 1')
+        queueMicrotask(() => {
+          log('timeout 1 -> immediate 1 -> nextTick 1 -> microtask 1')
+        })
+        queueMicrotask(() => {
+          process.nextTick(() => {
+            log(
+              'timeout 1 -> immediate 1 -> nextTick 1 -> microtask 2 -> nextTick'
+            )
+          })
+        })
+      })
+    })
+    setImmediate(() => {
+      log('timeout 1 -> immediate 2')
+    })
+    process.nextTick(() => {
+      log('timeout 1 -> nextTick 1')
+      queueMicrotask(() => {
+        log('timeout 1 -> nextTick 1 -> microtask 1')
+      })
+      queueMicrotask(() => {
+        process.nextTick(() => {
+          log('timeout 1 -> nextTick 1 -> microtask 2 -> nextTick')
+        })
+      })
+      process.nextTick(() => {
+        log('timeout 1 -> nextTick 1 -> nextTick 1')
+      })
+    })
+  })
+  setTimeout(() => {
+    runPendingImmediatesAfterCurrentTask()
+
+    log('timeout 2')
+    setImmediate(() => {
+      log('timeout 2 -> immediate 1')
+      setImmediate(() => {
+        log('timeout 2 -> immediate 1 -> immediate 1')
+      })
+    })
+  })
+  setTimeout(() => {
+    log('timeout 3')
+    done.resolve()
+  })
+
+  await done.promise
+
+  expect(logs).toEqual([
+    // ===================================
+    'timeout 1',
+    'timeout 1 -> nextTick 1',
+    'timeout 1 -> nextTick 1 -> nextTick 1',
+    'timeout 1 -> nextTick 1 -> microtask 1',
+    'timeout 1 -> nextTick 1 -> microtask 2 -> nextTick',
+    // ======================
+    'timeout 1 -> immediate 1',
+    'timeout 1 -> immediate 1 -> nextTick 1',
+    'timeout 1 -> immediate 1 -> nextTick 1 -> microtask 1',
+    'timeout 1 -> immediate 1 -> nextTick 1 -> microtask 2 -> nextTick',
+    // ======================
+    'timeout 1 -> immediate 2',
+    // ===================================
+    'timeout 2',
+    // ======================
+    'timeout 2 -> immediate 1',
+    // ======================
+    'timeout 2 -> immediate 1 -> immediate 1',
+    // ===================================
+    'timeout 3',
+  ])
+})