fix: allow connect again after close

lib/operations/connect.js

@@ -260,6 +260,18 @@ function connect(mongoClient, url, options, callback) {
     throw new Error('no callback function provided');
   }
 
+  // Has a connection already been established?
+  if (mongoClient.topology) {
+    if (mongoClient.topology.isConnected()) {
+      throw new Error('already connected');
+    }
+    // this is a reconnect, clear out old state
+    mongoClient.topology = undefined;
+    mongoClient.s.options = {};
+    mongoClient.s.dbCache = new Map();
+    mongoClient.s.sessions = new Set();
+  }
+
   let didRequestAuthentication = false;
   const logger = Logger('MongoClient', options);
 

package.json

@@ -68,7 +68,7 @@
     "test": "npm run lint && mocha --recursive test/functional test/unit test/core",
     "test-nolint": "mocha --recursive test/functional test/unit test/core",
     "coverage": "istanbul cover mongodb-test-runner -- -t 60000 test/core test/unit test/functional",
-    "lint": "eslint lib test",
+    "lint": "eslint -v && eslint lib test",
     "format": "prettier --print-width 100 --tab-width 2 --single-quote --write 'test/**/*.js' 'lib/**/*.js'",
     "bench": "node test/benchmarks/driverBench/",
     "generate-evergreen": "node .evergreen/generate_evergreen_tasks.js",

test/functional/connection.test.js

@@ -1,7 +1,8 @@
 'use strict';
-const test = require('./shared').assert,
-  setupDatabase = require('./shared').setupDatabase,
-  expect = require('chai').expect;
+const test = require('./shared').assert;
+const setupDatabase = require('./shared').setupDatabase;
+const withClient = require('./shared').withClient;
+const expect = require('chai').expect;
 
 describe('Connection', function() {
   before(function() {
@@ -514,4 +515,27 @@ describe('Connection', function() {
       });
     }
   });
+
+  it('should be able to connect again after close', function() {
+    return withClient(this.configuration.newClient(), client => done => {
+      expect(client.isConnected()).to.be.true;
+      const collection = () => client.db('testReconnect').collection('test');
+      collection().insertOne({ a: 1 }, (err, result) => {
+        expect(err).to.not.exist;
+        expect(result).to.exist;
+        client.close(err => {
+          expect(err).to.not.exist;
+          client.connect(err => {
+            expect(err).to.not.exist;
+            collection().insertOne({ b: 2 }, (err, result) => {
+              expect(err).to.not.exist;
+              expect(result).to.exist;
+              expect(client.topology.isDestroyed()).to.be.false;
+              done();
+            });
+          });
+        });
+      });
+    });
+  });
 });

test/functional/shared.js

@@ -78,9 +78,20 @@ function makeCleanupFn(client) {
 function withClient(client, operation, errorHandler) {
   const cleanup = makeCleanupFn(client);
 
+  function operationHandler(client) {
+    // run the operation
+    const result = operation(client);
+    // if it returns a callback, wrap it in a Promise
+    if (typeof result === 'function') {
+      return new Promise(done => result(done));
+    }
+    // otherwise assume it returned a Promise
+    return result;
+  }
+
   return client
     .connect()
-    .then(operation, errorHandler)
+    .then(operationHandler, errorHandler)
     .then(() => cleanup(), cleanup);
 }