chore(NODE-3521): find/agg cursor session always there

src/cursor/aggregation_cursor.ts

@@ -61,7 +61,7 @@ export class AggregationCursor<TSchema = Document> extends AbstractCursor<TSchem
   }
 
   /** @internal */
-  _initialize(session: ClientSession | undefined, callback: Callback<ExecutionResult>): void {
+  _initialize(session: ClientSession, callback: Callback<ExecutionResult>): void {
     const aggregateOperation = new AggregateOperation(this.namespace, this[kPipeline], {
       ...this[kOptions],
       ...this.cursorOptions,

src/cursor/find_cursor.ts

@@ -68,7 +68,7 @@ export class FindCursor<TSchema = Document> extends AbstractCursor<TSchema> {
   }
 
   /** @internal */
-  _initialize(session: ClientSession | undefined, callback: Callback<ExecutionResult>): void {
+  _initialize(session: ClientSession, callback: Callback<ExecutionResult>): void {
     const findOperation = new FindOperation(undefined, this.namespace, this[kFilter], {
       ...this[kBuiltOptions], // NOTE: order matters here, we may need to refine this
       ...this.cursorOptions,

test/unit/cursor/aggregation_cursor.test.js

@@ -0,0 +1,117 @@
+'use strict';
+
+const expect = require('chai').expect;
+const { MongoError } = require('../../../src/error');
+const mock = require('../../tools/mongodb-mock/index');
+const { Topology } = require('../../../src/sdam/topology');
+const { Long } = require('bson');
+const { MongoDBNamespace, isHello } = require('../../../src/utils');
+const { AggregationCursor } = require('../../../src/cursor/aggregation_cursor');
+
+const test = {};
+describe('Aggregation Cursor', function () {
+  describe('#next', function () {
+    afterEach(function () {
+      mock.cleanup();
+    });
+    beforeEach(function () {
+      return mock.createServer().then(mockServer => {
+        test.server = mockServer;
+      });
+    });
+
+    context('when there is a data bearing server', function () {
+      beforeEach(function () {
+        test.server.setMessageHandler(request => {
+          const doc = request.document;
+          if (isHello(doc)) {
+            request.reply(mock.HELLO);
+          } else if (doc.aggregate) {
+            request.reply({
+              cursor: {
+                id: Long.fromNumber(1),
+                ns: 'test.test',
+                firstBatch: [{ _id: 1, name: 'test' }]
+              },
+              ok: 1
+            });
+          }
+        });
+      });
+
+      it('sets the session on the cursor', function (done) {
+        const topology = new Topology(test.server.hostAddress());
+        const cursor = new AggregationCursor(topology, MongoDBNamespace.fromString('test.test'), [], {});
+        topology.connect(function () {
+          cursor.next(function () {
+            expect(cursor.session).to.exist;
+            topology.close(done);
+          });
+        });
+      });
+    });
+
+    context('when there is no data bearing server', function () {
+      beforeEach(function () {
+        test.server.setMessageHandler(request => {
+          const doc = request.document;
+          if (isHello(doc)) {
+            request.reply({ errmsg: 'network error' });
+          } else if (doc.aggregate) {
+            request.reply({
+              cursor: {
+                id: Long.fromNumber(1),
+                ns: 'test.test',
+                firstBatch: [{ _id: 1, name: 'test' }]
+              },
+              ok: 1
+            });
+          }
+        });
+      });
+
+      it('does not set the session on the cursor', function (done) {
+        const topology = new Topology(test.server.hostAddress(), { serverSelectionTimeoutMS: 2 });
+        const cursor = new AggregationCursor(topology, MongoDBNamespace.fromString('test.test'), [], {});
+        topology.connect(function () {
+          cursor.next(function () {
+            expect(cursor.session).to.not.exist;
+            topology.close(done);
+          });
+        });
+      });
+    });
+
+    context('when a data bearing server becomes available', function () {
+      beforeEach(function () {
+        let helloCalls = 0;
+        test.server.setMessageHandler(request => {
+          const doc = request.document;
+          if (isHello(doc)) {
+            request.reply(helloCalls > 0 ? { errmsg: 'network error' } : mock.HELLO);
+          } else if (doc.aggregate) {
+            request.reply({
+              cursor: {
+                id: Long.fromNumber(1),
+                ns: 'test.test',
+                firstBatch: [{ _id: 1, name: 'test' }]
+              },
+              ok: 1
+            });
+          }
+        });
+      });
+
+      it('sets the session on the cursor', function (done) {
+        const topology = new Topology(test.server.hostAddress(), { serverSelectionTimeoutMS: 2 });
+        const cursor = new AggregationCursor(topology, MongoDBNamespace.fromString('test.test'), [], {});
+        topology.connect(function () {
+          cursor.next(function () {
+            expect(cursor.session).to.exist;
+            topology.close(done);
+          });
+        });
+      });
+    });
+  });
+});

test/unit/cursor/find_cursor.test.js

@@ -12,7 +12,7 @@ const test = {};
 describe('Find Cursor', function () {
   describe('#next', function () {
     afterEach(function () {
-      mock.cleanup()
+      mock.cleanup();
     });
     beforeEach(function () {
       return mock.createServer().then(mockServer => {