Fix SSG data request failing with trailing slash (#10140)

* Fix SSG data request failing with trailing slash

* Update to re-use toRoute method

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

@@ -666,7 +666,7 @@ export default class Router implements BaseRouter {
 
   _getStaticData = (asPath: string, _cachedData?: object): Promise<object> => {
     let pathname = parse(asPath).pathname
-    pathname = !pathname || pathname === '/' ? '/index' : pathname
+    pathname = toRoute(!pathname || pathname === '/' ? '/index' : pathname)
 
     return process.env.NODE_ENV === 'production' &&
       (_cachedData = this.sdc[pathname])

test/integration/prerender/pages/index.js

@@ -14,7 +14,7 @@ const Page = ({ world, time }) => {
     <>
       <p>hello {world}</p>
       <span>time: {time}</span>
-      <Link href="/another">
+      <Link href="/another?hello=world" as="/another/?hello=world">
         <a id="another">to another</a>
       </Link>
       <br />

test/integration/prerender/test/index.test.js

@@ -134,9 +134,11 @@ const navigateTest = (dev = false) => {
 
     // go to /another
     async function goFromHomeToAnother() {
+      await browser.eval('window.beforeAnother = true')
       await browser.elementByCss('#another').click()
       await browser.waitForElementByCss('#home')
       text = await browser.elementByCss('p').text()
+      expect(await browser.eval('window.beforeAnother')).toBe(true)
       expect(text).toMatch(/hello.*?world/)
     }
     await goFromHomeToAnother()