worker: display MessagePort status in util.inspect()

PR-URL: #22658
Reviewed-By: Benjamin Gruenbaum <[email protected]>
Reviewed-By: Denys Otrishko <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Tiancheng "Timothy" Gu <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Ruben Bridgewater <[email protected]>

Author: addaleax

lib/internal/worker.js

@@ -125,6 +125,27 @@ MessagePort.prototype.close = function(cb) {
 const drainMessagePort = MessagePort.prototype.drain;
 delete MessagePort.prototype.drain;
 
+Object.defineProperty(MessagePort.prototype, util.inspect.custom, {
+  enumerable: false,
+  writable: false,
+  value: function inspect() {  // eslint-disable-line func-name-matching
+    let ref;
+    try {
+      // This may throw when `this` does not refer to a native object,
+      // e.g. when accessing the prototype directly.
+      ref = this.hasRef();
+    } catch { return this; }
+    return Object.assign(Object.create(MessagePort.prototype),
+                         ref === undefined ? {
+                           active: false,
+                         } : {
+                           active: true,
+                           refed: ref
+                         },
+                         this);
+  }
+});
+
 function setupPortReferencing(port, eventEmitter, eventName) {
   // Keep track of whether there are any workerMessage listeners:
   // If there are some, ref() the channel so it keeps the event loop alive.