Fix setImmediate() not triggering the timer if idle (#2)

Co-authored-by: Kasper Isager Dalsgarð <kasperisager@hey.com>

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
   }

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)
+  })
+})