From eedc66f8fc82a714963e452162dae406705d4bf7 Mon Sep 17 00:00:00 2001
From: Durran Jordan <durran@gmail.com>
Date: Tue, 22 Nov 2022 19:24:33 +0100
Subject: [PATCH 1/2] fix(NODE-4831): check map value is not undefined

---
 src/cmap/connection.ts            |  3 ++-
 test/unit/cmap/connection.test.ts | 28 ++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/src/cmap/connection.ts b/src/cmap/connection.ts
index 7aa913fbe40..265ea7a1c0d 100644
--- a/src/cmap/connection.ts
+++ b/src/cmap/connection.ts
@@ -384,7 +384,8 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
       } else {
         // Get the first orphaned operation description.
         const entry = this[kQueue].entries().next();
-        if (entry) {
+        /* eslint no-restricted-syntax: 0 */
+        if (entry.value !== undefined) {
           const [requestId, orphaned]: [number, OperationDescription] = entry.value;
           // If the orphaned operation description exists then set it.
           operationDescription = orphaned;
diff --git a/test/unit/cmap/connection.test.ts b/test/unit/cmap/connection.test.ts
index a9b95bcea2c..b6ab033a118 100644
--- a/test/unit/cmap/connection.test.ts
+++ b/test/unit/cmap/connection.test.ts
@@ -287,6 +287,34 @@ describe('new Connection()', function () {
         });
       });
 
+      context('when no operation description is in the queue', function () {
+        const document = { ok: 1 };
+
+        beforeEach(function () {
+          // @ts-expect-error: driverSocket does not fully satisfy the stream type, but that's okay
+          connection = sinon.spy(new Connection(driverSocket, connectionOptionsDefaults));
+          connection.isMonitoringConnection = true;
+          const queueSymbol = getSymbolFrom(connection, 'queue');
+          queue = connection[queueSymbol];
+        });
+
+        it('does not error', function () {
+          const msg = generateOpMsgBuffer(document);
+          const msgHeader: MessageHeader = {
+            length: msg.readInt32LE(0),
+            requestId: 2,
+            responseTo: 1,
+            opCode: msg.readInt32LE(12)
+          };
+          const msgBody = msg.subarray(16);
+
+          const message = new BinMsg(msg, msgHeader, msgBody);
+          expect(() => {
+            connection.onMessage(message);
+          }).to.not.throw(/undefined is not iterable/);
+        });
+      });
+
       context('when more than one operation description is in the queue', function () {
         let spyOne;
         let spyTwo;

From 48244b6bc88ff0defd79eef31320f6696df7549d Mon Sep 17 00:00:00 2001
From: Durran Jordan <durran@gmail.com>
Date: Tue, 22 Nov 2022 20:47:35 +0100
Subject: [PATCH 2/2] fix(NODE-4831): check for null

---
 src/cmap/connection.ts            | 3 +--
 test/unit/cmap/connection.test.ts | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/cmap/connection.ts b/src/cmap/connection.ts
index 265ea7a1c0d..85f60008174 100644
--- a/src/cmap/connection.ts
+++ b/src/cmap/connection.ts
@@ -384,8 +384,7 @@ export class Connection extends TypedEventEmitter<ConnectionEvents> {
       } else {
         // Get the first orphaned operation description.
         const entry = this[kQueue].entries().next();
-        /* eslint no-restricted-syntax: 0 */
-        if (entry.value !== undefined) {
+        if (entry.value != null) {
           const [requestId, orphaned]: [number, OperationDescription] = entry.value;
           // If the orphaned operation description exists then set it.
           operationDescription = orphaned;
diff --git a/test/unit/cmap/connection.test.ts b/test/unit/cmap/connection.test.ts
index b6ab033a118..5c8d872bb84 100644
--- a/test/unit/cmap/connection.test.ts
+++ b/test/unit/cmap/connection.test.ts
@@ -311,7 +311,7 @@ describe('new Connection()', function () {
           const message = new BinMsg(msg, msgHeader, msgBody);
           expect(() => {
             connection.onMessage(message);
-          }).to.not.throw(/undefined is not iterable/);
+          }).to.not.throw();
         });
       });