From c12711ebfeaf482be1cbccc748f6ae428e097420 Mon Sep 17 00:00:00 2001
From: Joyee Cheung <joyeec9h3@gmail.com>
Date: Mon, 7 Aug 2023 16:28:56 +0200
Subject: [PATCH] lib: implement WeakReference on top of JS WeakRef

The C++ implementation can now be done entirely in JS using WeakRef.
Re-implement it in JS instead to simplify the code.

PR-URL: https://github.com/nodejs/node/pull/49053
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
---
 lib/diagnostics_channel.js                    |  2 +-
 lib/domain.js                                 |  3 +-
 lib/internal/util.js                          | 34 +++++++++++++++++++
 test/fixtures/snapshot/weak-reference-gc.js   |  3 +-
 test/fixtures/snapshot/weak-reference.js      |  3 +-
 .../test-internal-util-weakreference.js       |  3 +-
 6 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/lib/diagnostics_channel.js b/lib/diagnostics_channel.js
index dae0e930a395e9..10d35054f56535 100644
--- a/lib/diagnostics_channel.js
+++ b/lib/diagnostics_channel.js
@@ -28,7 +28,7 @@ const {
 
 const { triggerUncaughtException } = internalBinding('errors');
 
-const { WeakReference } = internalBinding('util');
+const { WeakReference } = require('internal/util');
 
 // Can't delete when weakref count reaches 0 as it could increment again.
 // Only GC can be used as a valid time to clean up the channels map.
diff --git a/lib/domain.js b/lib/domain.js
index 51565795d72010..7da672a3691560 100644
--- a/lib/domain.js
+++ b/lib/domain.js
@@ -52,9 +52,8 @@ const {
 const { createHook } = require('async_hooks');
 const { useDomainTrampoline } = require('internal/async_hooks');
 
-// TODO(addaleax): Use a non-internal solution for this.
 const kWeak = Symbol('kWeak');
-const { WeakReference } = internalBinding('util');
+const { WeakReference } = require('internal/util');
 
 // Overwrite process.domain with a getter/setter that will allow for more
 // effective optimizations
diff --git a/lib/internal/util.js b/lib/internal/util.js
index 1e1a647e693876..3586084ba7b8bd 100644
--- a/lib/internal/util.js
+++ b/lib/internal/util.js
@@ -33,6 +33,7 @@ const {
   SafeMap,
   SafeSet,
   SafeWeakMap,
+  SafeWeakRef,
   StringPrototypeReplace,
   StringPrototypeToLowerCase,
   StringPrototypeToUpperCase,
@@ -797,6 +798,38 @@ function guessHandleType(fd) {
   return handleTypes[type];
 }
 
+class WeakReference {
+  #weak = null;
+  #strong = null;
+  #refCount = 0;
+  constructor(object) {
+    this.#weak = new SafeWeakRef(object);
+  }
+
+  incRef() {
+    this.#refCount++;
+    if (this.#refCount === 1) {
+      const derefed = this.#weak.deref();
+      if (derefed !== undefined) {
+        this.#strong = derefed;
+      }
+    }
+    return this.#refCount;
+  }
+
+  decRef() {
+    this.#refCount--;
+    if (this.#refCount === 0) {
+      this.#strong = null;
+    }
+    return this.#refCount;
+  }
+
+  get() {
+    return this.#weak.deref();
+  }
+}
+
 module.exports = {
   getLazy,
   assertCrypto,
@@ -855,4 +888,5 @@ module.exports = {
   kEnumerableProperty,
   setOwnProperty,
   pendingDeprecate,
+  WeakReference,
 };
diff --git a/test/fixtures/snapshot/weak-reference-gc.js b/test/fixtures/snapshot/weak-reference-gc.js
index 8dada530e77c2a..b6af6c46e3829a 100644
--- a/test/fixtures/snapshot/weak-reference-gc.js
+++ b/test/fixtures/snapshot/weak-reference-gc.js
@@ -1,7 +1,6 @@
 'use strict';
 
-const { internalBinding } = require('internal/test/binding');
-const { WeakReference } = internalBinding('util');
+const { WeakReference } = require('internal/util');
 const {
   setDeserializeMainFunction
 } = require('v8').startupSnapshot
diff --git a/test/fixtures/snapshot/weak-reference.js b/test/fixtures/snapshot/weak-reference.js
index 214d52fee185fe..1aefc6a1c07195 100644
--- a/test/fixtures/snapshot/weak-reference.js
+++ b/test/fixtures/snapshot/weak-reference.js
@@ -1,7 +1,6 @@
 'use strict';
 
-const { internalBinding } = require('internal/test/binding');
-const { WeakReference } = internalBinding('util');
+const { WeakReference } = require('internal/util');
 const {
   setDeserializeMainFunction
 } = require('v8').startupSnapshot
diff --git a/test/parallel/test-internal-util-weakreference.js b/test/parallel/test-internal-util-weakreference.js
index 75a00176bb095b..ef3c0943b1f83e 100644
--- a/test/parallel/test-internal-util-weakreference.js
+++ b/test/parallel/test-internal-util-weakreference.js
@@ -2,8 +2,7 @@
 'use strict';
 const common = require('../common');
 const assert = require('assert');
-const { internalBinding } = require('internal/test/binding');
-const { WeakReference } = internalBinding('util');
+const { WeakReference } = require('internal/util');
 
 let obj = { hello: 'world' };
 const ref = new WeakReference(obj);