perf: optimize happy path (nodejs#1955)

* perf: do not call url.format if not needed

* perf: return early on parseURL

* perf: remove the usage of url.format from serializer

lib/core/util.js

@@ -46,6 +46,12 @@ function buildURL (url, queryParams) {
 function parseURL (url) {
   if (typeof url === 'string') {
     url = new URL(url)
+
+    if (!/^https?:/.test(url.origin || url.protocol)) {
+      throw new InvalidArgumentError('invalid protocol')
+    }
+
+    return url
   }
 
   if (!url || typeof url !== 'object') {

lib/fetch/dataURL.js

@@ -1,6 +1,5 @@
 const assert = require('assert')
 const { atob } = require('buffer')
-const { format } = require('url')
 const { isValidHTTPToken, isomorphicDecode } = require('./util')
 
 const encoder = new TextEncoder()
@@ -118,7 +117,17 @@ function dataURLProcessor (dataURL) {
  * @param {boolean} excludeFragment
  */
 function URLSerializer (url, excludeFragment = false) {
-  return format(url, { fragment: !excludeFragment })
+  const href = url.href
+
+  if (!excludeFragment) {
+    return href
+  }
+
+  const hash = href.lastIndexOf('#')
+  if (hash === -1) {
+    return href
+  }
+  return href.slice(0, hash)
 }
 
 // https://infra.spec.whatwg.org/#collect-a-sequence-of-code-points