Make dynamic routes case-sensitive (vercel#15444)

Fixes vercel#15377
Closes vercel#15394

packages/next/next-server/lib/router/utils/route-regex.ts

@@ -107,15 +107,15 @@ export function getRouteRegex(
       .join('')
 
     return {
-      re: new RegExp(`^${parameterizedRoute}(?:/)?$`, 'i'),
+      re: new RegExp(`^${parameterizedRoute}(?:/)?$`),
       groups,
       routeKeys,
       namedRegex: `^${namedParameterizedRoute}(?:/)?$`,
     }
   }
 
   return {
-    re: new RegExp(`^${parameterizedRoute}(?:/)?$`, 'i'),
+    re: new RegExp(`^${parameterizedRoute}(?:/)?$`),
     groups,
   }
 }

test/integration/client-navigation/pages/dynamic/[slug]/route.js

@@ -0,0 +1,13 @@
+import React from 'react'
+
+export default class DynamicRoute extends React.Component {
+  static async getInitialProps({ query = { slug: 'default' } }) {
+    return {
+      query,
+    }
+  }
+
+  render() {
+    return <p>{this.props.query.slug}</p>
+  }
+}

test/integration/client-navigation/test/index.test.js

@@ -43,6 +43,7 @@ describe('Client Navigation', () => {
       '/url-prop-override',
 
       '/dynamic/ssr',
+      '/dynamic/[slug]/route',
 
       '/nav',
       '/nav/about',
@@ -1002,6 +1003,27 @@ describe('Client Navigation', () => {
       await browser.close()
     })
 
+    it('should get url dynamic param', async () => {
+      const browser = await webdriver(
+        context.appPort,
+        '/dynamic/dynamic-part/route'
+      )
+      expect(await browser.elementByCss('p').text()).toBe('dynamic-part')
+      await browser.close()
+    })
+
+    it('should 404 on wrong casing of url dynamic param', async () => {
+      const browser = await webdriver(
+        context.appPort,
+        '/dynamic/dynamic-part/RoUtE'
+      )
+      expect(await browser.elementByCss('h1').text()).toBe('404')
+      expect(await browser.elementByCss('h2').text()).toBe(
+        'This page could not be found.'
+      )
+      await browser.close()
+    })
+
     it('should not 404 for <page>/', async () => {
       const browser = await webdriver(context.appPort, '/nav/about/')
       const text = await browser.elementByCss('p').text()