fix(NODE-3386): listCollections result type definition (#2866)

src/db.ts

@@ -34,7 +34,11 @@ import {
   DropDatabaseOptions,
   DropCollectionOptions
 } from './operations/drop';
-import { ListCollectionsCursor, ListCollectionsOptions } from './operations/list_collections';
+import {
+  CollectionInfo,
+  ListCollectionsCursor,
+  ListCollectionsOptions
+} from './operations/list_collections';
 import { ProfilingLevelOperation, ProfilingLevelOptions } from './operations/profiling_level';
 import { RemoveUserOperation, RemoveUserOptions } from './operations/remove_user';
 import { RenameOperation, RenameOptions } from './operations/rename';
@@ -358,8 +362,25 @@ export class Db {
    * @param filter - Query to filter collections by
    * @param options - Optional settings for the command
    */
-  listCollections(filter?: Document, options?: ListCollectionsOptions): ListCollectionsCursor {
-    return new ListCollectionsCursor(this, filter || {}, resolveOptions(this, options));
+  listCollections(
+    filter: Document,
+    options: Exclude<ListCollectionsOptions, 'nameOnly'> & { nameOnly: true }
+  ): ListCollectionsCursor<Pick<CollectionInfo, 'name' | 'type'>>;
+  listCollections(
+    filter: Document,
+    options: Exclude<ListCollectionsOptions, 'nameOnly'> & { nameOnly: false }
+  ): ListCollectionsCursor<CollectionInfo>;
+  listCollections<
+    T extends Pick<CollectionInfo, 'name' | 'type'> | CollectionInfo =
+      | Pick<CollectionInfo, 'name' | 'type'>
+      | CollectionInfo
+  >(filter?: Document, options?: ListCollectionsOptions): ListCollectionsCursor<T>;
+  listCollections<
+    T extends Pick<CollectionInfo, 'name' | 'type'> | CollectionInfo =
+      | Pick<CollectionInfo, 'name' | 'type'>
+      | CollectionInfo
+  >(filter: Document = {}, options: ListCollectionsOptions = {}): ListCollectionsCursor<T> {
+    return new ListCollectionsCursor<T>(this, filter, resolveOptions(this, options));
   }
 
   /**

src/index.ts

@@ -269,7 +269,7 @@ export type {
   IndexDirection
 } from './operations/indexes';
 export type { InsertOneResult, InsertOneOptions, InsertManyResult } from './operations/insert';
-export type { ListCollectionsOptions } from './operations/list_collections';
+export type { ListCollectionsOptions, CollectionInfo } from './operations/list_collections';
 export type { ListDatabasesResult, ListDatabasesOptions } from './operations/list_databases';
 export type {
   MapFunction,

src/operations/is_capped.ts

@@ -22,7 +22,7 @@ export class IsCappedOperation extends AbstractOperation<boolean> {
     coll.s.db
       .listCollections(
         { name: coll.collectionName },
-        { ...this.options, readPreference: this.readPreference, session }
+        { ...this.options, nameOnly: false, readPreference: this.readPreference, session }
       )
       .toArray((err, collections) => {
         if (err || !collections) return callback(err);

src/operations/list_collections.ts

@@ -2,7 +2,7 @@ import { CommandOperation, CommandOperationOptions } from './command';
 import { Aspect, defineAspects } from './operation';
 import { maxWireVersion, Callback, getTopology, MongoDBNamespace } from '../utils';
 import * as CONSTANTS from '../constants';
-import type { Document } from '../bson';
+import type { Binary, Document } from '../bson';
 import type { Server } from '../sdam/server';
 import type { Db } from '../db';
 import { AbstractCursor } from '../cursor/abstract_cursor';
@@ -105,7 +105,21 @@ export class ListCollectionsOperation extends CommandOperation<string[]> {
 }
 
 /** @public */
-export class ListCollectionsCursor extends AbstractCursor {
+export interface CollectionInfo extends Document {
+  name: string;
+  type?: string;
+  options?: Document;
+  info?: {
+    readOnly?: false;
+    uuid?: Binary;
+  };
+  idIndex?: Document;
+}
+
+/** @public */
+export class ListCollectionsCursor<
+  T extends Pick<CollectionInfo, 'name' | 'type'> | CollectionInfo = CollectionInfo
+> extends AbstractCursor<T> {
   parent: Db;
   filter: Document;
   options?: ListCollectionsOptions;
@@ -117,7 +131,7 @@ export class ListCollectionsCursor extends AbstractCursor {
     this.options = options;
   }
 
-  clone(): ListCollectionsCursor {
+  clone(): ListCollectionsCursor<T> {
     return new ListCollectionsCursor(this.parent, this.filter, {
       ...this.options,
       ...this.cursorOptions

src/operations/options_operation.ts

@@ -23,15 +23,15 @@ export class OptionsOperation extends AbstractOperation<Document> {
     coll.s.db
       .listCollections(
         { name: coll.collectionName },
-        { ...this.options, readPreference: this.readPreference, session }
+        { ...this.options, nameOnly: false, readPreference: this.readPreference, session }
       )
       .toArray((err, collections) => {
         if (err || !collections) return callback(err);
         if (collections.length === 0) {
           return callback(new MongoDriverError(`collection ${coll.namespace} not found`));
         }
 
-        callback(err, collections[0].options || null);
+        callback(err, collections[0].options);
       });
   }
 }

test/types/list_collections.test-d.ts

@@ -0,0 +1,45 @@
+import { expectType, expectNotType } from 'tsd';
+
+import { MongoClient } from '../../src/mongo_client';
+import type { CollectionInfo, ListCollectionsCursor } from '../../src/operations/list_collections';
+
+const db = new MongoClient('').db();
+
+type EitherCollectionInfoResult = CollectionInfo | Pick<CollectionInfo, 'name' | 'type'>;
+
+// We default to the CollectionInfo result type
+expectType<ListCollectionsCursor<Pick<CollectionInfo, 'name' | 'type'> | CollectionInfo>>(
+  db.listCollections()
+);
+// By default it isn't narrowed to either type
+expectNotType<ListCollectionsCursor<Pick<CollectionInfo, 'name' | 'type'>>>(db.listCollections());
+expectNotType<ListCollectionsCursor<CollectionInfo>>(db.listCollections());
+
+// Testing each argument variation
+db.listCollections();
+db.listCollections({ a: 2 });
+db.listCollections({ a: 2 }, { batchSize: 2 });
+
+const collections = await db.listCollections().toArray();
+expectType<EitherCollectionInfoResult[]>(collections);
+
+const nameOnly = await db.listCollections({}, { nameOnly: true }).toArray();
+expectType<Pick<CollectionInfo, 'name' | 'type'>[]>(nameOnly);
+
+const fullInfo = await db.listCollections({}, { nameOnly: false }).toArray();
+expectType<CollectionInfo[]>(fullInfo);
+
+const couldBeEither = await db.listCollections({}, { nameOnly: Math.random() > 0.5 }).toArray();
+expectType<EitherCollectionInfoResult[]>(couldBeEither);
+
+// Showing here that:
+// regardless of the option the generic parameter can be used to coerce the result if need be
+// note the nameOnly: false, yet strings are returned
+const overridden = await db
+  .listCollections<Pick<CollectionInfo, 'name' | 'type'>>({}, { nameOnly: false })
+  .toArray();
+expectType<Pick<CollectionInfo, 'name' | 'type'>[]>(overridden);
+const overriddenWithToArray = await db
+  .listCollections({}, { nameOnly: false })
+  .toArray<Pick<CollectionInfo, 'name' | 'type'>>();
+expectType<Pick<CollectionInfo, 'name' | 'type'>[]>(overriddenWithToArray);