From e188e7789426e2b25f2044c80be109a272bdcb8b Mon Sep 17 00:00:00 2001
From: Olivier Dubuc <olivier@odubuc.ca>
Date: Wed, 18 Oct 2023 16:23:30 -0400
Subject: [PATCH] feat: support dequeue event to properly match enqueue
 counterpart

---
 lib/pool.js                                                | 2 ++
 promise.d.ts                                               | 1 +
 promise.js                                                 | 2 +-
 test/integration/promise-wrappers/test-promise-wrappers.js | 7 ++++++-
 typings/mysql/lib/Pool.d.ts                                | 1 +
 5 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/lib/pool.js b/lib/pool.js
index db54a7ab76..bc32be67d9 100644
--- a/lib/pool.js
+++ b/lib/pool.js
@@ -87,10 +87,12 @@ class Pool extends EventEmitter {
       // The connection has been removed from the pool and is no longer good.
       if (this._connectionQueue.length) {
         cb = this._connectionQueue.shift();
+        this.emit('dequeue', connection);
         process.nextTick(this.getConnection.bind(this, cb));
       }
     } else if (this._connectionQueue.length) {
       cb = this._connectionQueue.shift();
+      this.emit('dequeue', connection);
       process.nextTick(cb.bind(null, null, connection));
     } else {
       this._freeConnections.push(connection);
diff --git a/promise.d.ts b/promise.d.ts
index e9f3e08a1d..099ce564ee 100644
--- a/promise.d.ts
+++ b/promise.d.ts
@@ -90,6 +90,7 @@ export interface Pool extends Connection {
   on(event: 'acquire', listener: (connection: PoolConnection) => any): this;
   on(event: 'release', listener: (connection: PoolConnection) => any): this;
   on(event: 'enqueue', listener: () => any): this;
+  on(event: 'dequeue', listener: () => any): this;
 
   end(): Promise<void>;
 
diff --git a/promise.js b/promise.js
index 95c5808b45..a407c1b020 100644
--- a/promise.js
+++ b/promise.js
@@ -331,7 +331,7 @@ class PromisePool extends EventEmitter {
     super();
     this.pool = pool;
     this.Promise = thePromise || Promise;
-    inheritEvents(pool, this, ['acquire', 'connection', 'enqueue', 'release']);
+    inheritEvents(pool, this, ['acquire', 'connection', 'enqueue', 'release', 'dequeue']);
   }
 
   getConnection() {
diff --git a/test/integration/promise-wrappers/test-promise-wrappers.js b/test/integration/promise-wrappers/test-promise-wrappers.js
index 6a1fc17448..b860e43a7e 100644
--- a/test/integration/promise-wrappers/test-promise-wrappers.js
+++ b/test/integration/promise-wrappers/test-promise-wrappers.js
@@ -326,17 +326,22 @@ function testEventsPool() {
       assert.equal(this, pool);
       ++events;
     })
+    .once('dequeue', function() {
+      assert.equal(this, pool);
+      ++events;
+    })
     .once('release', function() {
       assert.equal(this, pool);
       ++events;
 
-      doneEventsPool = events === 4;
+      doneEventsPool = events === 5;
     });
   /* eslint-enable no-invalid-this */
 
   pool.pool.emit('acquire');
   pool.pool.emit('connection');
   pool.pool.emit('enqueue');
+  pool.pool.emit('dequeue');
   pool.pool.emit('release');
 
   for (const eventName in expectedListeners) {
diff --git a/typings/mysql/lib/Pool.d.ts b/typings/mysql/lib/Pool.d.ts
index 93f8499561..d95b901a90 100644
--- a/typings/mysql/lib/Pool.d.ts
+++ b/typings/mysql/lib/Pool.d.ts
@@ -68,6 +68,7 @@ declare class Pool extends QueryableBase(ExecutableBase(EventEmitter)) {
   on(event: 'acquire', listener: (connection: PoolConnection) => any): this;
   on(event: 'release', listener: (connection: PoolConnection) => any): this;
   on(event: 'enqueue', listener: () => any): this;
+  on(event: 'dequeue', listener: () => any): this;
 
   unprepare(sql: string): PrepareStatementInfo;