make parseRelativeUrl return a UrlObject (#16809)

Alternative to https://github.com/vercel/next.js/pull/16798

packages/next/client/page-loader.ts

@@ -12,7 +12,6 @@ import {
 import getAssetPathFromRoute from '../next-server/lib/router/utils/get-asset-path-from-route'
 import { isDynamicRoute } from '../next-server/lib/router/utils/is-dynamic'
 import { parseRelativeUrl } from '../next-server/lib/router/utils/parse-relative-url'
-import { searchParamsToUrlQuery } from '../next-server/lib/router/utils/querystring'
 
 export const looseToArray = <T extends {}>(input: any): T[] =>
   [].slice.call(input)
@@ -204,10 +203,7 @@ export default class PageLoader {
    * @param {string} asPath the URL as shown in browser (virtual path); used for dynamic routes
    */
   getDataHref(href: string, asPath: string, ssg: boolean) {
-    const { pathname: hrefPathname, searchParams, search } = parseRelativeUrl(
-      href
-    )
-    const query = searchParamsToUrlQuery(searchParams)
+    const { pathname: hrefPathname, query, search } = parseRelativeUrl(href)
     const { pathname: asPathname } = parseRelativeUrl(asPath)
     const route = normalizeRoute(hrefPathname)
 

packages/next/next-server/lib/router/router.ts

@@ -563,7 +563,7 @@ export default class Router implements BaseRouter {
 
     let parsed = parseRelativeUrl(url)
 
-    let { pathname, searchParams } = parsed
+    let { pathname, query } = parsed
 
     parsed = this._resolveHref(parsed, pages) as typeof parsed
 
@@ -572,8 +572,6 @@ export default class Router implements BaseRouter {
       url = formatWithValidation(parsed)
     }
 
-    const query = searchParamsToUrlQuery(searchParams)
-
     // url and as should always be prefixed with basePath by this
     // point by either next/link or router.push/replace so strip the
     // basePath from the pathname to match the pages dir 1-to-1

packages/next/next-server/lib/router/utils/parse-relative-url.ts

 import { getLocationOrigin } from '../../utils'
+import { searchParamsToUrlQuery } from './querystring'
 
 const DUMMY_BASE = new URL(
   typeof window === 'undefined' ? 'http://n' : getLocationOrigin()
@@ -29,7 +30,7 @@ export function parseRelativeUrl(url: string, base?: string) {
   }
   return {
     pathname,
-    searchParams,
+    query: searchParamsToUrlQuery(searchParams),
     search,
     hash,
     href: href.slice(DUMMY_BASE.origin.length),

packages/next/next-server/lib/router/utils/prepare-destination.ts

@@ -35,7 +35,7 @@ export default function prepareDestination(
 
     parsedDestination = {
       pathname,
-      searchParams,
+      query: searchParamsToUrlQuery(searchParams),
       hash,
       protocol,
       hostname,
@@ -45,9 +45,6 @@ export default function prepareDestination(
     }
   }
 
-  parsedDestination.query = searchParamsToUrlQuery(
-    parsedDestination.searchParams
-  )
   const destQuery = parsedDestination.query
   const destPath = `${parsedDestination.pathname!}${
     parsedDestination.hash || ''
@@ -108,7 +105,6 @@ export default function prepareDestination(
     parsedDestination.pathname = pathname
     parsedDestination.hash = `${hash ? '#' : ''}${hash || ''}`
     delete parsedDestination.search
-    delete parsedDestination.searchParams
   } catch (err) {
     if (err.message.match(/Expected .*? to not repeat, but got an array/)) {
       throw new Error(