timers: fix regression with clearImmediate()

This commit fixes a regression introduced in 0ed8839 that caused
additional queued immediate callbacks to be ignored if
`clearImmediate(immediate)` was called within the callback for
`immediate`.
PR-URL: #9086Fixes: #9084
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>

Author: mscdex

lib/timers.js

@@ -575,12 +575,21 @@ function processImmediate() {
 domain.enter();
 
 immediate._callback=immediate._onImmediate;
+
+// Save next in case `clearImmediate(immediate)` is called from callback
+varnext=immediate._idleNext;
+
 tryOnImmediate(immediate,tail);
 
 if(domain)
 domain.exit();
 
-immediate=immediate._idleNext;
+// If `clearImmediate(immediate)` wasn't called from the callback, use the
+// `immediate`'s next item
+if(immediate._idleNext)
+immediate=immediate._idleNext;
+else
+immediate=next;
 }
 
 // Only round-trip to C++ land if we have to. Calling clearImmediate() on an

test/parallel/test-timers-clearImmediate.js

@@ -0,0 +1,18 @@
+'use strict';
+require('../common');
+constassert=require('assert');
+
+constN=3;
+varcount=0;
+functionnext(){
+constimmediate=setImmediate(function(){
+clearImmediate(immediate);
+++count;
+});
+}
+for(vari=0;i<N;++i)
+next();
+
+process.on('exit',()=>{
+assert.strictEqual(count,N,`Expected ${N} immediate callback executions`);
+});