dns: refactor dns to more modern JavaScript

lib/dns.js

@@ -1,6 +1,5 @@
 'use strict';
 
-const net = require('net');
 const util = require('util');
 
 const cares = process.binding('cares_wrap');
@@ -11,7 +10,7 @@ const GetAddrInfoReqWrap = cares.GetAddrInfoReqWrap;
 const GetNameInfoReqWrap = cares.GetNameInfoReqWrap;
 const QueryReqWrap = cares.QueryReqWrap;
 
-const isIp = net.isIP;
+const isIp = cares.isIP;
 const isLegalPort = internalNet.isLegalPort;
 
 
@@ -38,6 +37,9 @@ function errnoException(err, syscall, hostname) {
   return ex;
 }
 
+function validIpVersion(isIpResult) {
+  return isIpResult !== 0;
+}
 
 // c-ares invokes a callback either synchronously or asynchronously,
 // but the dns API should always invoke a callback asynchronously.
@@ -62,7 +64,7 @@ function makeAsync(callback) {
   return function asyncCallback() {
     if (asyncCallback.immediately) {
       // The API already returned, we can invoke the callback immediately.
-      callback(...arguments);
+      callback.apply(null, arguments);
     } else {
       var args = new Array(arguments.length + 1);
       args[0] = callback;
@@ -95,13 +97,13 @@ function onlookupall(err, addresses) {
     return;
   }
 
-  const results = Array(addresses.length);
-  
+  const results = new Array(addresses.length);
+
   for (var i = 0; i < addresses.length; i++) {
-    results.push({
+    results[i] = {
       address: addresses[i],
       family: this.family || (addresses[i].indexOf(':') >= 0 ? 6 : 4)
-    });
+    };
   }
 
   this.callback(null, results);
@@ -182,7 +184,8 @@ exports.lookup = function lookup(hostname, options, callback) {
 
 function onlookupservice(err, host, service) {
   if (err) {
-    return this.callback(errnoException(err, 'getnameinfo', this.host));
+    this.callback(errnoException(err, 'getnameinfo', this.host));
+    return;
   }
 
   this.callback(null, host, service);
@@ -192,10 +195,10 @@ function onlookupservice(err, host, service) {
 // lookupService(address, port, callback)
 exports.lookupService = function(host, port, callback) {
   if (arguments.length !== 3) {
-    throw new Error('Invalid arguments');
+    throw new TypeError(`Expected 3 arguments, got ${arguments.length}`);
   }
 
-  if (cares.isIP(host) === 0) {
+  if (isIP(host) === 0) {
     throw new TypeError('"host" argument needs to be a valid IP address');
   }
 
@@ -236,9 +239,10 @@ function resolver(bindingName) {
 
   return function query(name, callback) {
     if (typeof name !== 'string') {
-      throw new Error('"name" argument must be a string');
+      const msg = `"name" argument must be a string, got ${typeof name}`;
+      throw new TypeError(msg);
     } else if (typeof callback !== 'function') {
-      throw new Error('"callback" argument must be a function');
+      throw new TypeError('"callback" argument must be a function');
     }
 
     callback = makeAsync(callback);
@@ -272,7 +276,7 @@ exports.resolveSoa = resolveMap.SOA = resolver('querySoa');
 exports.reverse = resolver('getHostByAddr');
 
 
-exports.resolve = function(hostname, type_, callback_) {
+exports.resolve = (hostname, type_, callback_) => {
   var resolver, callback;
   if (typeof type_ === 'string') {
     resolver = resolveMap[type_];
@@ -292,42 +296,37 @@ exports.resolve = function(hostname, type_, callback_) {
 };
 
 
-exports.getServers = function() {
+exports.getServers = () => {
   return cares.getServers();
 };
 
 
 exports.setServers = function(servers) {
   // cache the original servers because in the event of an error setting the
   // servers cares won't have any servers available for resolution
-  var orig = cares.getServers();
-
-  var newSet = [];
+  var originalServers = cares.getServers();
 
-  servers.forEach(function(serv) {
-    var ver = isIp(serv);
+  const newSet = servers.map((serv) => {
+    var ipVersion = isIp(serv);
 
-    if (ver) {
-      newSet.push([ver, serv]);
-      return;
+    if (validIpVersion(ipVersion)) {
+      return [ver, serv];
     }
-    var match = serv.match(/\[(.*)\](:\d+)?/);
+    const match = serv.match(/\[(.*)\](:\d+)?/);
 
     // we have an IPv6 in brackets
     if (match) {
-      ver = isIp(match[1]);
-      if (ver) {
-        newSet.push([ver, match[1]]);
-        return;
+      ipVersion = isIp(match[1]);
+      if (validIpVersion(ipVersion)) {
+        return [ver, match[1]];
       }
     }
 
     var s = serv.split(/:\d+$/)[0];
-    ver = isIp(s);
+    ipVersion = isIp(s);
 
-    if (ver) {
-      newSet.push([ver, s]);
-      return;
+    if (validIpVersion(ipVersion)) {
+      return [ver, s];
     }
 
     throw new Error(`IP address is not properly formatted: ${serv}`);
@@ -337,7 +336,7 @@ exports.setServers = function(servers) {
 
   if (errorNumber !== 0) {
     // reset the servers to the old servers, because ares probably unset them
-    cares.setServers(orig.join(','));
+    cares.setServers(originalServers.join(','));
 
     var err = cares.strerror(r);
     throw new Error(`c-ares failed to set servers: ${err} [${servers}]`);