fix(shell-api): Add support for running aggregate database with a single stage MONGOSH-1868

packages/shell-api/src/collection.ts

@@ -164,7 +164,7 @@ export default class Collection extends ShellApiWithMongoClass {
   async aggregate(
     pipeline: Document[],
     options: Document & { explain: ExplainVerbosityLike }
-  ): Promise<Document>;
+  ): Promise<AggregationCursor>;
   async aggregate(...stages: Document[]): Promise<AggregationCursor>;
   @returnsPromise
   @returnType('AggregationCursor')
@@ -191,7 +191,10 @@ export default class Collection extends ShellApiWithMongoClass {
       this._database._name,
       this._name,
       pipeline,
-      { ...(await this._database._baseOptions()), ...aggOptions },
+      {
+        ...(await this._database._baseOptions()),
+        ...aggOptions,
+      },
       dbOptions
     );
     const cursor = new AggregationCursor(this._mongo, providerCursor);

packages/shell-api/src/database.spec.ts

@@ -400,6 +400,16 @@ describe('Database', function () {
         );
       });
 
+      it('supports a single aggregation stage', async function () {
+        await database.aggregate({ $piplelineStage: {} }, { options: true });
+
+        expect(serviceProvider.aggregateDb).to.have.been.calledWith(
+          database._name,
+          [{ $piplelineStage: {} }],
+          { options: true }
+        );
+      });
+
       it('calls serviceProvider.aggregateDb with explicit batchSize', async function () {
         await database.aggregate([{ $piplelineStage: {} }], {
           options: true,

packages/shell-api/src/database.ts

@@ -412,6 +412,14 @@ export default class Database extends ShellApiWithMongoClass {
     return await this._runAdminCommand(cmd, {});
   }
 
+  async aggregate(
+    singleStage: Document,
+    options?: Document
+  ): Promise<AggregationCursor>;
+  async aggregate(
+    pipeline: Document[],
+    options?: Document
+  ): Promise<AggregationCursor>;
   /**
    * Run an aggregation against the db.
    *
@@ -423,15 +431,20 @@ export default class Database extends ShellApiWithMongoClass {
   @returnType('AggregationCursor')
   @apiVersions([1])
   async aggregate(
-    pipeline: Document[],
+    pipelineOrSingleStage: Document | Document[],
     options?: Document
   ): Promise<AggregationCursor> {
     if ('background' in (options ?? {})) {
       await this._instanceState.printWarning(
         aggregateBackgroundOptionNotSupportedHelp
       );
     }
+    const pipeline: Document[] = Array.isArray(pipelineOrSingleStage)
+      ? pipelineOrSingleStage
+      : [pipelineOrSingleStage];
+
     assertArgsDefinedType([pipeline], [true], 'Database.aggregate');
+
     this._emitDatabaseApiCall('aggregate', { options, pipeline });
 
     const { aggOptions, dbOptions, explain } = adaptAggregateOptions(options);
@@ -1429,6 +1442,7 @@ export default class Database extends ShellApiWithMongoClass {
         CommonErrors.CommandFailed
       );
     }
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
     for (const cmdDescription of Object.values(result.commands) as Document[]) {
       if ('slaveOk' in cmdDescription) {
         cmdDescription.secondaryOk = cmdDescription.slaveOk;