fix(NODE-6276): preserve top level error code MongoWriteConcernError

src/bulk/common.ts

@@ -616,8 +616,8 @@ function handleMongoWriteConcernError(
   callback(
     new MongoBulkWriteError(
       {
-        message: err.result?.writeConcernError.errmsg,
-        code: err.result?.writeConcernError.result
+        message: err?.result.writeConcernError.errmsg,
+        code: err?.result.writeConcernError.code
       },
       new BulkWriteResult(bulkResult, isOrdered)
     )

src/error.ts

@@ -1158,14 +1158,30 @@ export class MongoServerSelectionError extends MongoSystemError {
   }
 }
 
+/**
+ * The type of the result property of MongoWriteConcernError
+ * @public
+ */
+export interface WriteConcernErrorResult {
+  writeConcernError: {
+    code: number;
+    errmsg: string;
+    codeName?: string;
+    errInfo?: Document;
+  };
+  ok: 0 | 1;
+  code?: number;
+  [x: string | number]: unknown;
+}
+
 /**
  * An error thrown when the server reports a writeConcernError
  * @public
  * @category Error
  */
 export class MongoWriteConcernError extends MongoServerError {
   /** The result document */
-  result: Document;
+  result: WriteConcernErrorResult;
 
   /**
    * **Do not use this constructor!**
@@ -1178,18 +1194,11 @@ export class MongoWriteConcernError extends MongoServerError {
    *
    * @public
    **/
-  constructor(result: {
-    writeConcernError: {
-      code: number;
-      errmsg: string;
-      codeName?: string;
-      errInfo?: Document;
-    };
-    errorLabels?: string[];
-  }) {
-    super({ ...result, ...result.writeConcernError });
-    this.errInfo = result.writeConcernError.errInfo;
+  constructor(result: WriteConcernErrorResult) {
+    super(result);
+    this.errInfo = result.writeConcernError?.errInfo;
     this.result = result;
+    this.code = result.code ? result.code : undefined;
   }
 
   override get name(): string {
@@ -1237,7 +1246,9 @@ export function needsRetryableWriteLabel(error: Error, maxWireVersion: number):
   }
 
   if (error instanceof MongoWriteConcernError) {
-    return RETRYABLE_WRITE_ERROR_CODES.has(error.result?.code ?? error.code ?? 0);
+    return RETRYABLE_WRITE_ERROR_CODES.has(
+      error.result.writeConcernError?.code ?? error?.code ?? 0
+    );
   }
 
   if (error instanceof MongoError && typeof error.code === 'number') {

test/unit/error.test.ts

@@ -30,7 +30,8 @@ import {
   setDifference,
   type TopologyDescription,
   type TopologyOptions,
-  WaitQueueTimeoutError as MongoWaitQueueTimeoutError
+  WaitQueueTimeoutError as MongoWaitQueueTimeoutError,
+  WriteConcernErrorResult
 } from '../mongodb';
 import { ReplSetFixture } from '../tools/common';
 import { cleanup } from '../tools/mongodb-mock/index';
@@ -740,4 +741,33 @@ describe('MongoErrors', () => {
       });
     });
   });
+
+  describe('MongoWriteConcernError constructor', function () {
+    context('when no top-level code is provided and writeConcernError.code exists', function () {
+      it('error.code remains undefined', function () {
+        const res: WriteConcernErrorResult = {
+          writeConcernError: {
+            code: 81, // nested code
+            errmsg: 'fake msg'
+          },
+          ok: 1
+        };
+        expect(new MongoWriteConcernError(res).code).to.equal(undefined);
+      });
+    });
+    context('when top-level code is provided and  writeConcernError.code exists', function () {
+      it('error.code equals the top-level code', function () {
+        const topLevelCode = 10;
+        const res: WriteConcernErrorResult = {
+          writeConcernError: {
+            code: 81, // nested code
+            errmsg: 'fake msg'
+          },
+          ok: 1,
+          code: topLevelCode
+        };
+        expect(new MongoWriteConcernError(res).code).to.equal(topLevelCode);
+      });
+    });
+  });
 });

test/unit/mongo_client.test.ts

@@ -737,7 +737,7 @@ describe('MongoClient', function () {
     expect(error).to.have.property('code', 'EBADNAME');
   });
 
-  it('srvServiceName should not error if it is greater than 15 characters as long as the DNS query limit is not surpassed', async () => {
+  it.only('srvServiceName should not error if it is greater than 15 characters as long as the DNS query limit is not surpassed', async () => {
     const options = parseOptions('mongodb+srv://localhost.a.com', {
       srvServiceName: 'a'.repeat(16)
     });