fix(NODE-6763): pass WriteConcernOptions instead on WriteConcernSettings

src/utils.ts

@@ -531,9 +531,11 @@ export function resolveOptions<T extends CommandOperationOptions>(
     if (writeConcern) {
       if (timeoutMS != null) {
         writeConcern = WriteConcern.fromOptions({
-          ...writeConcern,
-          wtimeout: undefined,
-          wtimeoutMS: undefined
+          writeConcern: {
+            ...writeConcern,
+            wtimeout: undefined,
+            wtimeoutMS: undefined
+          }
         });
       }
       result.writeConcern = writeConcern;

test/integration/read-write-concern/write_concern.test.ts

@@ -304,4 +304,51 @@ describe('Write Concern', function () {
       }
     });
   });
+
+  describe('NODE-6763: write concern is still added with timeoutMS is set', function () {
+    let client: MongoClient;
+    let collection: Collection;
+    const commands: CommandStartedEvent[] = [];
+
+    beforeEach(async function () {
+      client = this.configuration.newClient({}, { monitorCommands: true });
+      client.on('commandStarted', filterForCommands('insert', commands));
+      collection = client.db('foo').collection('bar');
+    });
+
+    afterEach(async function () {
+      await client.close();
+      commands.length = 0;
+    });
+
+    context('when the write concern includes only timeouts', function () {
+      it('the writeConcern is not added to the command.', async function () {
+        await collection.insertOne(
+          { name: 'john doe' },
+          { timeoutMS: 1000, writeConcern: { wtimeout: 1000 } }
+        );
+        const [
+          {
+            command: { writeConcern }
+          }
+        ] = commands;
+        expect(writeConcern).not.to.exist;
+      });
+    });
+
+    context('when the write concern includes only non-timeout values (`w`)', function () {
+      it('the writeConcern is added to the command.', async function () {
+        await collection.insertOne(
+          { name: 'john doe' },
+          { timeoutMS: 1000, writeConcern: { wtimeout: 1000, w: 'majority' } }
+        );
+        const [
+          {
+            command: { writeConcern }
+          }
+        ] = commands;
+        expect(writeConcern).to.deep.equal({ w: 'majority' });
+      });
+    });
+  });
 });