feat(NODE-4184)!: don't throw on aggregate with write concern and explain (mongodb#4718)

Author: durran

src/operations/aggregate.ts

@@ -80,12 +80,6 @@ export class AggregateOperation extends CommandOperation<CursorResponse> {
       delete this.options.writeConcern;
     }
 
-    if (this.explain && this.writeConcern) {
-      throw new MongoInvalidArgumentError(
-        'Option "explain" cannot be used on an aggregate call with writeConcern'
-      );
-    }
-
     if (options?.cursor != null && typeof options.cursor !== 'object') {
       throw new MongoInvalidArgumentError('Cursor options must be an object');
     }

test/integration/crud/aggregation.test.ts

@@ -1,6 +1,6 @@
 import { expect } from 'chai';
 
-import { MongoInvalidArgumentError } from '../../../src/error';
+import { MongoInvalidArgumentError, MongoServerError } from '../../../src/error';
 import { type MongoClient } from '../../../src/mongo_client';
 import { filterForCommands } from '../shared';
 
@@ -601,7 +601,7 @@ describe('Aggregation', function () {
       .toArray()
       .catch(error => error);
 
-    expect(error).to.be.instanceOf(MongoInvalidArgumentError);
+    expect(error).to.be.instanceOf(MongoServerError);
   });
 
   it('should fail if you try to use explain flag with { writeConcern: { j: true } }', async function () {
@@ -615,7 +615,7 @@ describe('Aggregation', function () {
       .toArray()
       .catch(error => error);
 
-    expect(error).to.be.instanceOf(MongoInvalidArgumentError);
+    expect(error).to.be.instanceOf(MongoServerError);
   });
 
   it('should ensure MaxTimeMS is correctly passed down into command execution when using a cursor', async function () {

test/unit/operations/aggregate.test.js renamed to test/unit/operations/aggregate.test.ts

@@ -1,31 +1,31 @@
-'use strict';
+import { expect } from 'chai';
 
-const { expect } = require('chai');
-const { AggregateOperation } = require('../../../src/operations/aggregate');
+import { AggregateOperation } from '../../../src/operations/aggregate';
+import { MongoDBNamespace, WriteConcern } from '../../mongodb';
 
 describe('AggregateOperation', function () {
-  const db = 'test';
+  const ns = new MongoDBNamespace('test', 'coll');
 
   describe('#constructor', function () {
     context('when out is in the options', function () {
-      const operation = new AggregateOperation(db, [], { out: 'test', dbName: db });
+      const operation = new AggregateOperation(ns, [], { out: 'test', dbName: ns.db });
 
       it('sets hasWriteStage to true', function () {
         expect(operation.hasWriteStage).to.be.true;
       });
     });
 
     context('when $out is the last stage', function () {
-      const operation = new AggregateOperation(db, [{ $out: 'test' }], { dbName: db });
+      const operation = new AggregateOperation(ns, [{ $out: 'test' }], { dbName: ns.db });
 
       it('sets hasWriteStage to true', function () {
         expect(operation.hasWriteStage).to.be.true;
       });
     });
 
     context('when $out is not the last stage', function () {
-      const operation = new AggregateOperation(db, [{ $out: 'test' }, { $project: { name: 1 } }], {
-        dbName: db
+      const operation = new AggregateOperation(ns, [{ $out: 'test' }, { $project: { name: 1 } }], {
+        dbName: ns.db
       });
 
       it('sets hasWriteStage to false', function () {
@@ -34,7 +34,9 @@ describe('AggregateOperation', function () {
     });
 
     context('when $merge is the last stage', function () {
-      const operation = new AggregateOperation(db, [{ $merge: { into: 'test' } }], { dbName: db });
+      const operation = new AggregateOperation(ns, [{ $merge: { into: 'test' } }], {
+        dbName: ns.db
+      });
 
       it('sets hasWriteStage to true', function () {
         expect(operation.hasWriteStage).to.be.true;
@@ -43,9 +45,9 @@ describe('AggregateOperation', function () {
 
     context('when $merge is not the last stage', function () {
       const operation = new AggregateOperation(
-        db,
+        ns,
         [{ $merge: { into: 'test' } }, { $project: { name: 1 } }],
-        { dbName: db }
+        { dbName: ns.db }
       );
 
       it('sets hasWriteStage to false', function () {
@@ -54,19 +56,33 @@ describe('AggregateOperation', function () {
     });
 
     context('when no writable stages in empty pipeline', function () {
-      const operation = new AggregateOperation(db, [], { dbName: db });
+      const operation = new AggregateOperation(ns, [], { dbName: ns.db });
 
       it('sets hasWriteStage to false', function () {
         expect(operation.hasWriteStage).to.be.false;
       });
     });
 
     context('when no writable stages', function () {
-      const operation = new AggregateOperation(db, [{ $project: { name: 1 } }], { dbName: db });
+      const operation = new AggregateOperation(ns, [{ $project: { name: 1 } }], { dbName: ns });
 
       it('sets hasWriteStage to false', function () {
         expect(operation.hasWriteStage).to.be.false;
       });
     });
+
+    context('when explain is set', function () {
+      context('when writeConcern is set', function () {
+        const operation = new AggregateOperation(ns, [], {
+          dbName: ns.db,
+          explain: true,
+          writeConcern: WriteConcern.fromOptions({ wtimeoutMS: 1000 })
+        });
+
+        it('does not raise an error', function () {
+          expect(operation.explain).to.exist;
+        });
+      });
+    });
   });
 });