feat(dns): added support for a custom lookup function; (#5339)

lib/adapters/http.js

@@ -23,6 +23,7 @@ import EventEmitter from 'events';
 import formDataToStream from "../helpers/formDataToStream.js";
 import readBlob from "../helpers/readBlob.js";
 import ZlibHeaderTransformStream from '../helpers/ZlibHeaderTransformStream.js';
+import callbackify from "../helpers/callbackify.js";
 
 const zlibOptions = {
   flush: zlib.constants.Z_SYNC_FLUSH,
@@ -146,13 +147,24 @@ const wrapAsync = (asyncExecutor) => {
 /*eslint consistent-return:0*/
 export default isHttpAdapterSupported && function httpAdapter(config) {
   return wrapAsync(async function dispatchHttpRequest(resolve, reject, onDone) {
-    let {data} = config;
+    let {data, lookup, family} = config;
     const {responseType, responseEncoding} = config;
     const method = config.method.toUpperCase();
     let isDone;
     let rejected = false;
     let req;
 
+    if (lookup && utils.isAsyncFn(lookup)) {
+      lookup = callbackify(lookup, (entry) => {
+        if(utils.isString(entry)) {
+          entry = [entry, entry.indexOf('.') < 0 ? 6 : 4]
+        } else if (!utils.isArray(entry)) {
+          throw new TypeError('lookup async function must return an array [ip: string, family: number]]')
+        }
+        return entry;
+      })
+    }
+
     // temporary internal emitter until the AxiosRequest class will be implemented
     const emitter = new EventEmitter();
 
@@ -378,6 +390,8 @@ export default isHttpAdapterSupported && function httpAdapter(config) {
       agents: { http: config.httpAgent, https: config.httpsAgent },
       auth,
       protocol,
+      family,
+      lookup,
       beforeRedirect: dispatchBeforeRedirect,
       beforeRedirects: {}
     };

lib/helpers/callbackify.js

@@ -0,0 +1,16 @@
+import utils from "../utils.js";
+
+const callbackify = (fn, reducer) => {
+  return utils.isAsyncFn(fn) ? function (...args) {
+    const cb = args.pop();
+    fn.apply(this, args).then((value) => {
+      try {
+        reducer ? cb(null, ...reducer(value)) : cb(null, value);
+      } catch (err) {
+        cb(err);
+      }
+    }, cb);
+  } : fn;
+}
+
+export default callbackify;

lib/utils.js

@@ -662,6 +662,15 @@ const toJSONObject = (obj) => {
   return visit(obj, 0);
 }
 
+const [isPlainFunction, isAsyncFn, isGeneratorFn, isAsyncGeneratorFn] = (
+  (...fns) => fns.map(
+    ({constructor})=> (thing) => thing && typeof thing === 'function' && thing.constructor === constructor
+  )
+)(()=> {}, async()=>{}, function*(){}, async function*(){});
+
+const isThenable = (thing) =>
+  thing && (isObject(thing) || isFunction(thing)) && isFunction(thing.then) && isFunction(thing.catch);
+
 export default {
   isArray,
   isArrayBuffer,
@@ -711,5 +720,10 @@ export default {
   ALPHABET,
   generateString,
   isSpecCompliantForm,
-  toJSONObject
+  toJSONObject,
+  isAsyncFn,
+  isGeneratorFn,
+  isAsyncGeneratorFn,
+  isPlainFunction,
+  isThenable
 };