feat(mongo-client): remove deprecated logout and print warning

Logging out on a connected MongoClient has been disallowed since
the v3.0.0 major release due to incompatibilities with v3.6+ of
the server. A warning is now printed alerting users who might
still erroneously be using this feature.

lib/mongo_client.js

@@ -7,10 +7,10 @@ const executeOperation = require('./utils').executeOperation;
 const handleCallback = require('./utils').handleCallback;
 const inherits = require('util').inherits;
 const MongoError = require('mongodb-core').MongoError;
+const deprecate = require('util').deprecate;
 
 // Operations
 const connectOp = require('./operations/mongo_client_ops').connectOp;
-const logout = require('./operations/mongo_client_ops').logout;
 const validOptions = require('./operations/mongo_client_ops').validOptions;
 
 /**
@@ -170,25 +170,10 @@ MongoClient.prototype.connect = function(callback) {
   });
 };
 
-/**
- * Logout user from server, fire off on all connections and remove all auth info
- * @method
- * @param {object} [options] Optional settings.
- * @param {string} [options.dbName] Logout against different database than current.
- * @param {Db~resultCallback} [callback] The command result callback
- * @return {Promise} returns Promise if no callback passed
- */
-MongoClient.prototype.logout = function(options, callback) {
+MongoClient.prototype.logout = deprecate(function(options, callback) {
   if (typeof options === 'function') (callback = options), (options = {});
-  options = options || {};
-
-  // Establish the correct database name
-  const dbName = this.s.options.authSource ? this.s.options.authSource : this.s.options.dbName;
-
-  return executeOperation(this, logout, [this, dbName, callback], {
-    skipSessions: true
-  });
-};
+  callback(null, true);
+}, 'Multiple authentication is prohibited on a connected client, please only authenticate once per MongoClient');
 
 /**
  * Close the db and its underlying connections

lib/operations/mongo_client_ops.js

@@ -521,21 +521,6 @@ function legacyTransformUrlOptions(object) {
   return mergeOptions(createUnifiedOptions({}, object), object, false);
 }
 
-/**
- * Logout user from server, fire off on all connections and remove all auth info.
- *
- * @method
- * @param {MongoClient} mongoClient The MongoClient instance on which to logout.
- * @param {object} [options] Optional settings. See MongoClient.prototype.logout for a list of options.
- * @param {Db~resultCallback} [callback] The command result callback
- */
-function logout(mongoClient, dbName, callback) {
-  mongoClient.topology.logout(dbName, err => {
-    if (err) return callback(err);
-    callback(null, true);
-  });
-}
-
 function mergeOptions(target, source, flatten) {
   for (const name in source) {
     if (source[name] && typeof source[name] === 'object' && flatten) {
@@ -688,4 +673,4 @@ function validOptions(options) {
   }
 }
 
-module.exports = { connectOp, logout, validOptions };
+module.exports = { connectOp, validOptions };

lib/topologies/topology_base.js

@@ -375,11 +375,6 @@ class TopologyBase extends EventEmitter {
     this.s.coreTopology.auth.apply(this.s.coreTopology, args);
   }
 
-  logout() {
-    var args = Array.prototype.slice.call(arguments, 0);
-    this.s.coreTopology.logout.apply(this.s.coreTopology, args);
-  }
-
   /**
    * All raw connections
    * @method