refactor!: CreateIndexOp returns string, CreateIndexesOp returns array (

#2666)

`CreateIndexesOperation` was returning the name of the created index
instead of the result from the server because of the logic ensuring
`CreateIndexOperation` has that behavior.

This PR makes `CreateIndexesOperation` return an *array of index names*
(breaking change), while `CreateIndexOperation` continues to return a
single index name string. This makes the behavior consistent with other
official drivers.

Users in need of the raw result from the server should use `db.command`.

NODE-2602

src/bulk/common.ts

@@ -1221,7 +1221,10 @@ export abstract class BulkOperationBase {
   }
 
   /** An internal helper method. Do not invoke directly. Will be going away in the future */
-  execute(options?: BulkWriteOptions, callback?: Callback<BulkWriteResult>): Promise<void> | void {
+  execute(
+    options?: BulkWriteOptions,
+    callback?: Callback<BulkWriteResult>
+  ): Promise<BulkWriteResult> | void {
     if (typeof options === 'function') (callback = options), (options = {});
     options = options ?? {};
 
@@ -1303,7 +1306,7 @@ Object.defineProperty(BulkOperationBase.prototype, 'length', {
 function handleEarlyError(
   err?: AnyError,
   callback?: Callback<BulkWriteResult>
-): Promise<void> | void {
+): Promise<BulkWriteResult> | void {
   const Promise = PromiseProvider.get();
   if (typeof callback === 'function') {
     callback(err);

src/collection.ts

@@ -744,19 +744,19 @@ export class Collection {
    * await collection.createIndex(['j', ['k', -1], { l: '2d' }])
    * ```
    */
-  createIndex(indexSpec: IndexSpecification): Promise<Document>;
-  createIndex(indexSpec: IndexSpecification, callback: Callback<Document>): void;
-  createIndex(indexSpec: IndexSpecification, options: CreateIndexesOptions): Promise<Document>;
+  createIndex(indexSpec: IndexSpecification): Promise<string>;
+  createIndex(indexSpec: IndexSpecification, callback: Callback<string>): void;
+  createIndex(indexSpec: IndexSpecification, options: CreateIndexesOptions): Promise<string>;
   createIndex(
     indexSpec: IndexSpecification,
     options: CreateIndexesOptions,
-    callback: Callback<Document>
+    callback: Callback<string>
   ): void;
   createIndex(
     indexSpec: IndexSpecification,
-    options?: CreateIndexesOptions | Callback<Document>,
-    callback?: Callback<Document>
-  ): Promise<Document> | void {
+    options?: CreateIndexesOptions | Callback<string>,
+    callback?: Callback<string>
+  ): Promise<string> | void {
     if (typeof options === 'function') (callback = options), (options = {});
 
     return executeOperation(
@@ -798,19 +798,19 @@ export class Collection {
    * ]);
    * ```
    */
-  createIndexes(indexSpecs: IndexDescription[]): Promise<Document>;
-  createIndexes(indexSpecs: IndexDescription[], callback: Callback<Document>): void;
-  createIndexes(indexSpecs: IndexDescription[], options: CreateIndexesOptions): Promise<Document>;
+  createIndexes(indexSpecs: IndexDescription[]): Promise<string[]>;
+  createIndexes(indexSpecs: IndexDescription[], callback: Callback<string[]>): void;
+  createIndexes(indexSpecs: IndexDescription[], options: CreateIndexesOptions): Promise<string[]>;
   createIndexes(
     indexSpecs: IndexDescription[],
     options: CreateIndexesOptions,
-    callback: Callback<Document>
+    callback: Callback<string[]>
   ): void;
   createIndexes(
     indexSpecs: IndexDescription[],
-    options?: CreateIndexesOptions | Callback<Document>,
-    callback?: Callback<Document>
-  ): Promise<Document> | void {
+    options?: CreateIndexesOptions | Callback<string[]>,
+    callback?: Callback<string[]>
+  ): Promise<string[]> | void {
     if (typeof options === 'function') (callback = options), (options = {});
     options = options ? Object.assign({}, options) : {};
     if (typeof options.maxTimeMS !== 'number') delete options.maxTimeMS;

src/db.ts

@@ -579,25 +579,25 @@ export class Db {
    * @param options - Optional settings for the command
    * @param callback - An optional callback, a Promise will be returned if none is provided
    */
-  createIndex(name: string, indexSpec: IndexSpecification): Promise<Document>;
-  createIndex(name: string, indexSpec: IndexSpecification, callback?: Callback<Document>): void;
+  createIndex(name: string, indexSpec: IndexSpecification): Promise<string>;
+  createIndex(name: string, indexSpec: IndexSpecification, callback?: Callback<string>): void;
   createIndex(
     name: string,
     indexSpec: IndexSpecification,
     options: CreateIndexesOptions
-  ): Promise<Document>;
+  ): Promise<string>;
   createIndex(
     name: string,
     indexSpec: IndexSpecification,
     options: CreateIndexesOptions,
-    callback: Callback<Document>
+    callback: Callback<string>
   ): void;
   createIndex(
     name: string,
     indexSpec: IndexSpecification,
-    options?: CreateIndexesOptions | Callback<Document>,
-    callback?: Callback<Document>
-  ): Promise<Document> | void {
+    options?: CreateIndexesOptions | Callback<string>,
+    callback?: Callback<string>
+  ): Promise<string> | void {
     if (typeof options === 'function') (callback = options), (options = {});
 
     return executeOperation(

src/operations/indexes.ts

@@ -154,10 +154,11 @@ export class IndexesOperation extends AbstractOperation<Document> {
 }
 
 /** @internal */
-export class CreateIndexesOperation extends CommandOperation<Document> {
+export class CreateIndexesOperation<
+  T extends string | string[] = string[]
+> extends CommandOperation<T> {
   options: CreateIndexesOptions;
   collectionName: string;
-  onlyReturnNameOfCreatedIndex?: boolean;
   indexes: IndexDescription[];
 
   constructor(
@@ -172,12 +173,9 @@ export class CreateIndexesOperation extends CommandOperation<Document> {
     this.collectionName = collectionName;
 
     this.indexes = indexes;
-    if (indexes.length === 1) {
-      this.onlyReturnNameOfCreatedIndex = true;
-    }
   }
 
-  execute(server: Server, session: ClientSession, callback: Callback<Document>): void {
+  execute(server: Server, session: ClientSession, callback: Callback<T>): void {
     const options = this.options;
     const indexes = this.indexes;
 
@@ -223,19 +221,20 @@ export class CreateIndexesOperation extends CommandOperation<Document> {
     // collation is set on each index, it should not be defined at the root
     this.options.collation = undefined;
 
-    super.executeCommand(server, session, cmd, (err, result) => {
+    super.executeCommand(server, session, cmd, err => {
       if (err) {
         callback(err);
         return;
       }
 
-      callback(undefined, this.onlyReturnNameOfCreatedIndex ? indexes[0].name : result);
+      const indexNames = indexes.map(index => index.name || '');
+      callback(undefined, indexNames as T);
     });
   }
 }
 
 /** @internal */
-export class CreateIndexOperation extends CreateIndexesOperation {
+export class CreateIndexOperation extends CreateIndexesOperation<string> {
   constructor(
     parent: OperationParent,
     collectionName: string,
@@ -250,6 +249,12 @@ export class CreateIndexOperation extends CreateIndexesOperation {
 
     super(parent, collectionName, [makeIndexSpec(indexSpec, options)], options);
   }
+  execute(server: Server, session: ClientSession, callback: Callback<string>): void {
+    super.execute(server, session, (err, indexNames) => {
+      if (err || !indexNames) return callback(err);
+      return callback(undefined, indexNames[0]);
+    });
+  }
 }
 
 /** @internal */

test/functional/index.test.js

@@ -831,10 +831,8 @@ describe('Indexes', function () {
     }
   });
 
-  it('should correctly execute createIndexes', {
-    metadata: {
-      requires: { mongodb: '>=2.6.0', topology: ['single', 'ssl', 'heap', 'wiredtiger'] }
-    },
+  it('should correctly execute createIndexes with multiple indexes', {
+    metadata: { requires: { mongodb: '>=2.6.0', topology: ['single'] } },
 
     test: function (done) {
       var configuration = this.configuration;
@@ -845,7 +843,7 @@ describe('Indexes', function () {
           [{ key: { a: 1 } }, { key: { b: 1 }, name: 'hello1' }],
           function (err, r) {
             expect(err).to.not.exist;
-            test.equal(3, r.numIndexesAfter);
+            expect(r).to.deep.equal(['a_1', 'hello1']);
 
             db.collection('createIndexes')
               .listIndexes()
@@ -868,6 +866,38 @@ describe('Indexes', function () {
     }
   });
 
+  it('should correctly execute createIndexes with one index', {
+    metadata: { requires: { mongodb: '>=2.6.0', topology: ['single'] } },
+
+    test: function (done) {
+      var configuration = this.configuration;
+      var client = configuration.newClient(configuration.writeConcernMax(), { maxPoolSize: 1 });
+      client.connect(function (err, client) {
+        var db = client.db(configuration.db);
+        db.collection('createIndexes').createIndexes([{ key: { a: 1 } }], function (err, r) {
+          expect(err).to.not.exist;
+          expect(r).to.deep.equal(['a_1']);
+
+          db.collection('createIndexes')
+            .listIndexes()
+            .toArray(function (err, docs) {
+              expect(err).to.not.exist;
+              var keys = {};
+
+              for (var i = 0; i < docs.length; i++) {
+                keys[docs[i].name] = true;
+              }
+
+              test.ok(keys['a_1']);
+              test.ok(keys['hello1']);
+
+              client.close(done);
+            });
+        });
+      });
+    }
+  });
+
   it('shouldCorrectlyCreateTextIndex', {
     metadata: {
       requires: { topology: ['single', 'replicaset', 'sharded', 'ssl', 'heap', 'wiredtiger'] }