refactor: simplify connect, reuse a set for error event names

Author: mbroadst

lib/core/connection/connect.js

@@ -20,34 +20,14 @@ function connect(options, callback) {
     AUTH_PROVIDERS = defaultAuthProviders(options.bson);
   }
 
-  if (options.family !== void 0) {
-    makeConnection(options.family, options, (err, socket) => {
-      if (err) {
-        callback(err, socket); // in the error case, `socket` is the originating error event name
-        return;
-      }
-
-      performInitialHandshake(new ConnectionType(socket, options), options, callback);
-    });
-
-    return;
-  }
-
-  return makeConnection(6, options, (err, ipv6Socket) => {
+  const family = options.family !== void 0 ? options.family : 0;
+  makeConnection(family, options, (err, socket) => {
     if (err) {
-      makeConnection(0, options, (err, ipv4Socket) => {
-        if (err) {
-          callback(err, ipv4Socket); // in the error case, `ipv4Socket` is the originating error event name
-          return;
-        }
-
-        performInitialHandshake(new ConnectionType(ipv4Socket, options), options, callback);
-      });
-
+      callback(err, socket); // in the error case, `socket` is the originating error event name
       return;
     }
 
-    performInitialHandshake(new ConnectionType(ipv6Socket, options), options, callback);
+    performInitialHandshake(new ConnectionType(socket, options), options, callback);
   });
 }
 
@@ -238,6 +218,7 @@ function parseSslOptions(family, options) {
   return result;
 }
 
+const SOCKET_ERROR_EVENTS = new Set(['error', 'close', 'timeout', 'parseError']);
 function makeConnection(family, options, _callback) {
   const useSsl = typeof options.ssl === 'boolean' ? options.ssl : false;
   const keepAlive = typeof options.keepAlive === 'boolean' ? options.keepAlive : true;
@@ -279,17 +260,16 @@ function makeConnection(family, options, _callback) {
   socket.setTimeout(connectionTimeout);
   socket.setNoDelay(noDelay);
 
-  const errorEvents = ['error', 'close', 'timeout', 'parseError'];
   function errorHandler(eventName) {
     return err => {
-      errorEvents.forEach(event => socket.removeAllListeners(event));
+      SOCKET_ERROR_EVENTS.forEach(event => socket.removeAllListeners(event));
       socket.removeListener('connect', connectHandler);
       callback(connectionFailureError(eventName, err), eventName);
     };
   }
 
   function connectHandler() {
-    errorEvents.forEach(event => socket.removeAllListeners(event));
+    SOCKET_ERROR_EVENTS.forEach(event => socket.removeAllListeners(event));
     if (socket.authorizationError && rejectUnauthorized) {
       return callback(socket.authorizationError);
     }
@@ -298,10 +278,7 @@ function makeConnection(family, options, _callback) {
     callback(null, socket);
   }
 
-  socket.once('error', errorHandler('error'));
-  socket.once('close', errorHandler('close'));
-  socket.once('timeout', errorHandler('timeout'));
-  socket.once('parseError', errorHandler('parseError'));
+  SOCKET_ERROR_EVENTS.forEach(event => socket.once(event, errorHandler(event)));
   socket.once('connect', connectHandler);
 }