lib: run microtasks before ticks

ronag · ronag · commit 9df2edf92b26 · 2023-12-24T11:39:16.000+01:00
This resolve multiple timing issues related to promises and nextTick. As well as resolving zaldo in promise only code, i.e. our current best practice of using process.nextTick will always apply and work. Refs: nodejs#51156 Refs: nodejs#51156 (comment) Refs: nodejs#51114 Refs: nodejs#51070 Refs: nodejs#51156 PR-URL: nodejs#51267
diff --git a/doc/api/cli.md b/doc/api/cli.md
@@ -787,6 +787,20 @@ Use this flag to generate a blob that can be injected into the Node.js
 binary to produce a [single executable application][]. See the documentation
 about [this configuration][`--experimental-sea-config`] for details.
 
+
+### `--experimental-task-ordering`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+> Stability: 1 - Experimental
+
+Enable experimental task ordering. Always drain micro task queue
+before running `process.nextTick` to avoid unintuitive behavior
+and unexpected logical deadlocks when mixing async callback and
+event API's with `Promise`, `async`/`await`` and `queueMicroTask`.
+
 ### `--experimental-shadow-realm`
 
 <!-- YAML
diff --git a/lib/internal/process/task_queues.js b/lib/internal/process/task_queues.js
@@ -41,6 +41,7 @@ const {
 
 const { AsyncResource } = require('async_hooks');
 
+let experimentalTaskOrdering;
 // *Must* match Environment::TickInfo::Fields in src/env.h.
 const kHasTickScheduled = 0;
 
@@ -65,8 +66,16 @@ function runNextTicks() {
 }
 
 function processTicksAndRejections() {
+  if (experimentalTaskOrdering === undeifned) {
+    const { getOptionValue } = require('internal/options');
+    experimentalTaskOrdering = getOptionValue('--experimental-task-ordering');
+  }
+
   let tock;
   do {
+    if (experimentalTaskOrdering) {
+      runMicrotasks();
+    }
     while ((tock = queue.shift()) !== null) {
       const asyncId = tock[async_id_symbol];
       emitBefore(asyncId, tock[trigger_async_id_symbol], tock);
@@ -92,7 +101,9 @@ function processTicksAndRejections() {
 
       emitAfter(asyncId);
     }
-    runMicrotasks();
+    if (!experimentalTaskOrdering) {
+      runMicrotasks();
+    }
   } while (!queue.isEmpty() || processPromiseRejections());
   setHasTickScheduled(false);
   setHasRejectionToWarn(false);
