From 4e4c72b5e61e2b5261f5286d257e934291060fa4 Mon Sep 17 00:00:00 2001
From: Mathias Buus <mathiasbuus@gmail.com>
Date: Tue, 1 Oct 2024 20:10:17 +0200
Subject: [PATCH] Fix `setImmediate()` not triggering the timer if idle (#2)
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Co-authored-by: Kasper Isager Dalsgarð <kasperisager@hey.com>
---
 index.js          |  8 ++++++++
 test/immediate.js | 12 ++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/index.js b/index.js
index efd5107..57d8261 100644
--- a/index.js
+++ b/index.js
@@ -251,6 +251,7 @@ function ontimer () {
 
 function onimmediate () {
   const now = Date.now()
+  const timerRunning = queue.length > 0
 
   let uncaughtError = null
 
@@ -267,6 +268,13 @@ function onimmediate () {
 
   tick()
 
+  // some reentry wants the timers to start but they are not, lets start them
+  if (!timerRunning && queue.length > 0) {
+    const l = queue.peek()
+    nextExpiry = l.expiry
+    updateTimer(l.ms)
+  }
+
   if (uncaughtError !== null) {
     throw uncaughtError
   }
diff --git a/test/immediate.js b/test/immediate.js
index 8a2e7d3..abed1bf 100644
--- a/test/immediate.js
+++ b/test/immediate.js
@@ -125,3 +125,15 @@ test('setImmediate following setTimeout', async function (t) {
 
   clearTimeout(timer)
 })
+
+test('setImmediate that triggers setTimeout', async function (t) {
+  t.plan(2)
+
+  timers.setImmediate(() => {
+    t.pass('immediate triggered')
+
+    timers.setTimeout(() => {
+      t.pass('timeout triggered')
+    }, 20)
+  })
+})