Add DNS cache

package.json

@@ -40,6 +40,7 @@
 		"@sindresorhus/is": "^0.15.0",
 		"@szmarczak/http-timer": "^1.1.2",
 		"@types/p-cancelable": "^1.0.0",
+		"cacheable-lookup": "^0.1.0",
 		"cacheable-request": "^6.0.0",
 		"debug": "^4.1.1",
 		"decompress-response": "^4.0.0",

readme.md

@@ -328,7 +328,14 @@ If this is disabled, a compressed response is returned as a `Buffer`. This may b
 Type: `Object`<br>
 Default: `false`
 
-[Cache adapter instance](#cache-adapters) for storing cached data.
+[Cache adapter instance](#cache-adapters) for storing cached response data.
+
+###### dnsCache
+
+Type: `Object`<br>
+Default: `false`
+
+[Cache adapter instance](#cache-adapters) for storing cached DNS data.
 
 ###### request
 
@@ -806,7 +813,7 @@ The promise returned by Got has a [`.cancel()`](https://github.com/sindresorhus/
 <a name="cache-adapters"></a>
 ## Cache
 
-Got implements [RFC 7234](http://httpwg.org/specs/rfc7234.html) compliant HTTP caching which works out of the box in-memory and is easily pluggable with a wide range of storage adapters. Fresh cache entries are served directly from the cache, and stale cache entries are revalidated with `If-None-Match`/`If-Modified-Since` headers. You can read more about the underlying cache behavior in the [`cacheable-request` documentation](https://github.com/lukechilds/cacheable-request).
+Got implements [RFC 7234](http://httpwg.org/specs/rfc7234.html) compliant HTTP caching which works out of the box in-memory and is easily pluggable with a wide range of storage adapters. Fresh cache entries are served directly from the cache, and stale cache entries are revalidated with `If-None-Match`/`If-Modified-Since` headers. You can read more about the underlying cache behavior in the [`cacheable-request` documentation](https://github.com/lukechilds/cacheable-request). For DNS cache, Got uses [`cacheable-lookup`](https://github.com/szmarczak/cacheable-lookup).
 
 You can use the JavaScript `Map` type as an in-memory cache:
 

source/as-stream.ts

@@ -76,13 +76,13 @@ export default function asStream(options: MergedOptions) {
 			throw new Error('Failed to pipe. The response has been emitted already.');
 		}
 
-		const result = pipe(destination, options);
+		pipe(destination, options);
 
 		if (Reflect.has(destination, 'setHeader')) {
 			piped.add(destination);
 		}
 
-		return result;
+		return destination;
 	};
 
 	proxy.unpipe = stream => {

source/index.js

@@ -48,6 +48,7 @@ const defaults = {
 		followRedirect: true,
 		stream: false,
 		cache: false,
+		dnsCache: false,
 		useElectronNet: false,
 		responseType: 'text',
 		resolveBodyOnly: false

source/normalize-arguments.js

@@ -1,6 +1,7 @@
 'use strict';
 const {URL, URLSearchParams} = require('url'); // TODO: Use the `URL` global when targeting Node.js 10
 const urlLib = require('url');
+const CacheableLookup = require('cacheable-lookup');
 const is = require('@sindresorhus/is');
 const lowercaseKeys = require('lowercase-keys');
 const urlToOptions = require('./utils/url-to-options').default;
@@ -93,6 +94,12 @@ const preNormalize = (options, defaults) => {
 		options.retry.errorCodes = new Set(options.retry.errorCodes);
 	}
 
+	if (options.dnsCache) {
+		const cacheableLookup = new CacheableLookup({cacheAdapter: options.dnsCache});
+		options.lookup = cacheableLookup.lookup;
+		delete options.dnsCache;
+	}
+
 	return options;
 };
 

test/cache.js

@@ -143,3 +143,10 @@ test('doesn\'t cache response when received HTTP error', async t => {
 	t.is(statusCode, 200);
 	t.deepEqual(body, 'ok');
 });
+
+test('dns cache works', async t => {
+	const map = new Map();
+	await t.notThrowsAsync(got('https://example.com', {dnsCache: map}));
+
+	t.is(map.size, 1);
+});