feat(NODE-5233)!: prevent session from one client from being used on another

src/mongo_client.ts

@@ -598,7 +598,14 @@ export class MongoClient extends TypedEventEmitter<MongoClientEvents> {
     return client.connect();
   }
 
-  /** Starts a new session on the server */
+  /**
+   * Creates a new ClientSession. When using the returned session in an operation
+   * a corresponding ServerSession will be created.
+   *
+   * @remarks
+   * A ClientSession instance may only be passed to operations being performed on the same
+   * MongoClient it was started from.
+   */
   startSession(options?: ClientSessionOptions): ClientSession {
     const session = new ClientSession(
       this,

src/operations/execute_operation.ts

@@ -118,6 +118,8 @@ async function executeOperationAsync<
     throw new MongoExpiredSessionError('Use of expired sessions is not permitted');
   } else if (session.snapshotEnabled && !topology.capabilities.supportsSnapshotReads) {
     throw new MongoCompatibilityError('Snapshot reads require MongoDB 5.0 or later');
+  } else if (session.client !== client) {
+    throw new MongoRuntimeError('ClientSession must be from the same MongoClient');
   }
 
   const readPreference = operation.readPreference ?? ReadPreference.primary;

test/integration/sessions/sessions.prose.test.ts

@@ -6,11 +6,46 @@ import {
   type Collection,
   type CommandStartedEvent,
   MongoClient,
-  MongoDriverError
+  MongoDriverError,
+  MongoRuntimeError
 } from '../../mongodb';
 import { sleep } from '../../tools/utils';
 
 describe('Sessions Prose Tests', () => {
+  describe('5. Session argument is for the right client', () => {
+    let client1: MongoClient;
+    let client2: MongoClient;
+    beforeEach(async function () {
+      client1 = this.configuration.newClient();
+      client2 = this.configuration.newClient();
+    });
+
+    afterEach(async function () {
+      await client1?.close();
+      await client2?.close();
+    });
+
+    /**
+     * Steps:
+     * - Create client1 and client2
+     * - Get database from client1
+     * - Get collection from database
+     * - Start session from client2
+     * - Call collection.insertOne(session,...)
+     * - Assert that an error was reported because session was not started from client1
+     */
+    context('when session is started from a different client than operation is being run on', () =>
+      it('the operation throws a MongoRuntimeError', async () => {
+        const db = client1.db();
+        const collection = db.collection('test');
+        const session = client2.startSession();
+        const error = await collection.insertOne({}, { session }).catch(error => error);
+        expect(error).to.be.instanceOf(MongoRuntimeError);
+        expect(error).to.match(/ClientSession must be from the same MongoClient/i);
+      })
+    );
+  });
+
   describe('14. Implicit sessions only allocate their server session after a successful connection checkout', () => {
     let client: MongoClient;
     let testCollection: Collection<{ _id: number; a?: number }>;