Add experimental caseSensitiveRoutes config

packages/next/src/build/index.ts

@@ -712,6 +712,7 @@ export default async function build(
           varyHeader: typeof RSC_VARY_HEADER
         }
         skipMiddlewareUrlNormalize?: boolean
+        caseSensitive?: boolean
       } = nextBuildSpan.traceChild('generate-routes-manifest').traceFn(() => {
         const sortedRoutes = getSortedRoutes([
           ...pageKeys.pages,
@@ -731,6 +732,7 @@ export default async function build(
         return {
           version: 3,
           pages404: true,
+          caseSensitive: !!config.experimental.caseSensitiveRoutes,
           basePath: config.basePath,
           redirects: redirects.map((r: any) => buildCustomRoute(r, 'redirect')),
           headers: headers.map((r: any) => buildCustomRoute(r, 'header')),

packages/next/src/server/base-server.ts

@@ -783,6 +783,7 @@ export default abstract class Server<ServerOptions extends Options = Options> {
             i18n: this.nextConfig.i18n,
             basePath: this.nextConfig.basePath,
             rewrites: this.customRoutes.rewrites,
+            caseSensitive: !!this.nextConfig.experimental.caseSensitiveRoutes,
           })
 
           // Ensure parsedUrl.pathname includes locale before processing

packages/next/src/server/config-schema.ts

@@ -270,6 +270,9 @@ const configSchema = {
         craCompat: {
           type: 'boolean',
         },
+        caseSensitiveRoutes: {
+          type: 'boolean',
+        },
         useDeploymentId: {
           type: 'boolean',
         },

packages/next/src/server/config-shared.ts

@@ -144,6 +144,7 @@ export interface NextJsWebpackConfig {
 }
 
 export interface ExperimentalConfig {
+  caseSensitiveRoutes?: boolean
   useDeploymentId?: boolean
   useDeploymentIdServerActions?: boolean
   deploymentId?: string
@@ -663,6 +664,7 @@ export const defaultConfig: NextConfig = {
   output: !!process.env.NEXT_PRIVATE_STANDALONE ? 'standalone' : undefined,
   modularizeImports: undefined,
   experimental: {
+    caseSensitiveRoutes: false,
     useDeploymentId: false,
     deploymentId: undefined,
     useDeploymentIdServerActions: false,

packages/next/src/server/next-server.ts

@@ -1335,6 +1335,8 @@ export default class NextNodeServer extends BaseServer {
       ...publicRoutes,
       ...staticFilesRoutes,
     ]
+    const caseSensitiveRoutes =
+      !!this.nextConfig.experimental.caseSensitiveRoutes
 
     const restrictedRedirectPaths = this.nextConfig.basePath
       ? [`${this.nextConfig.basePath}/_next`]
@@ -1345,14 +1347,22 @@ export default class NextNodeServer extends BaseServer {
       this.minimalMode || this.isRenderWorker
         ? []
         : this.customRoutes.headers.map((rule) =>
-            createHeaderRoute({ rule, restrictedRedirectPaths })
+            createHeaderRoute({
+              rule,
+              restrictedRedirectPaths,
+              caseSensitive: caseSensitiveRoutes,
+            })
           )
 
     const redirects =
       this.minimalMode || this.isRenderWorker
         ? []
         : this.customRoutes.redirects.map((rule) =>
-            createRedirectRoute({ rule, restrictedRedirectPaths })
+            createRedirectRoute({
+              rule,
+              restrictedRedirectPaths,
+              caseSensitive: caseSensitiveRoutes,
+            })
           )
 
     const rewrites = this.generateRewrites({ restrictedRedirectPaths })
@@ -2044,6 +2054,7 @@ export default class NextNodeServer extends BaseServer {
           type: 'rewrite',
           rule: rewrite,
           restrictedRedirectPaths,
+          caseSensitive: !!this.nextConfig.experimental.caseSensitiveRoutes,
         })
         return {
           ...rewriteRoute,

packages/next/src/server/server-route-utils.ts

@@ -24,21 +24,25 @@ export function getCustomRoute(params: {
   rule: Header
   type: RouteType
   restrictedRedirectPaths: string[]
+  caseSensitive: boolean
 }): Route & Header
 export function getCustomRoute(params: {
   rule: Rewrite
   type: RouteType
   restrictedRedirectPaths: string[]
+  caseSensitive: boolean
 }): Route & Rewrite
 export function getCustomRoute(params: {
   rule: Redirect
   type: RouteType
   restrictedRedirectPaths: string[]
+  caseSensitive: boolean
 }): Route & Redirect
 export function getCustomRoute(params: {
   rule: Rewrite | Redirect | Header
   type: RouteType
   restrictedRedirectPaths: string[]
+  caseSensitive: boolean
 }): (Route & Rewrite) | (Route & Header) | (Route & Rewrite) {
   const { rule, type, restrictedRedirectPaths } = params
   const match = getPathMatch(rule.source, {
@@ -51,6 +55,7 @@ export function getCustomRoute(params: {
             type === 'redirect' ? restrictedRedirectPaths : undefined
           )
       : undefined,
+    sensitive: params.caseSensitive,
   })
 
   return {
@@ -65,14 +70,17 @@ export function getCustomRoute(params: {
 export const createHeaderRoute = ({
   rule,
   restrictedRedirectPaths,
+  caseSensitive,
 }: {
   rule: Header
   restrictedRedirectPaths: string[]
+  caseSensitive: boolean
 }): Route => {
   const headerRoute = getCustomRoute({
     type: 'header',
     rule,
     restrictedRedirectPaths,
+    caseSensitive,
   })
   return {
     match: headerRoute.match,
@@ -134,14 +142,17 @@ export const stringifyQuery = (req: BaseNextRequest, query: ParsedUrlQuery) => {
 export const createRedirectRoute = ({
   rule,
   restrictedRedirectPaths,
+  caseSensitive,
 }: {
   rule: Redirect
   restrictedRedirectPaths: string[]
+  caseSensitive: boolean
 }): Route => {
   const redirectRoute = getCustomRoute({
     type: 'redirect',
     rule,
     restrictedRedirectPaths,
+    caseSensitive,
   })
   return {
     internal: redirectRoute.internal,

packages/next/src/server/server-utils.ts

@@ -97,6 +97,7 @@ export function getUtils({
   rewrites,
   pageIsDynamic,
   trailingSlash,
+  caseSensitive,
 }: {
   page: string
   i18n?: NextConfig['i18n']
@@ -108,6 +109,7 @@ export function getUtils({
   }
   pageIsDynamic: boolean
   trailingSlash?: boolean
+  caseSensitive: boolean
 }) {
   let defaultRouteRegex: ReturnType<typeof getNamedRouteRegex> | undefined
   let dynamicRouteMatcher: RouteMatchFn | undefined
@@ -140,6 +142,7 @@ export function getUtils({
         {
           removeUnnamedParams: true,
           strict: true,
+          sensitive: !!caseSensitive,
         }
       )
       let params = matcher(parsedUrl.pathname)

packages/next/src/shared/lib/router/utils/path-match.ts

@@ -18,6 +18,11 @@ interface Options {
    * to match.
    */
   strict?: boolean
+
+  /**
+   * When true the matcher will be case-sensitive, defaults to false
+   */
+  sensitive?: boolean
 }
 
 /**
@@ -29,7 +34,8 @@ export function getPathMatch(path: string, options?: Options) {
   const keys: Key[] = []
   const regexp = pathToRegexp(path, keys, {
     delimiter: '/',
-    sensitive: false,
+    sensitive:
+      typeof options?.sensitive === 'boolean' ? options.sensitive : false,
     strict: options?.strict,
   })
 

test/integration/custom-routes/next.config.js

@@ -1,4 +1,7 @@
 module.exports = {
+  experimental: {
+    caseSensitiveRoutes: true,
+  },
   async rewrites() {
     // no-rewrites comment
     return {

test/integration/custom-routes/test/index.test.js

@@ -39,6 +39,44 @@ let appPort
 let app
 
 const runTests = (isDev = false, isTurbo = false) => {
+  it.each([
+    {
+      path: '/to-ANOTHER',
+      content: /could not be found/,
+      status: 404,
+    },
+    {
+      path: '/HELLO-world',
+      content: /could not be found/,
+      status: 404,
+    },
+    {
+      path: '/docs/GITHUB',
+      content: /could not be found/,
+      status: 404,
+    },
+    {
+      path: '/add-HEADER',
+      content: /could not be found/,
+      status: 404,
+    },
+  ])(
+    'should honor caseSensitiveRoutes config for $path',
+    async ({ path, status, content }) => {
+      const res = await fetchViaHTTP(appPort, path, undefined, {
+        redirect: 'manual',
+      })
+
+      if (status) {
+        expect(res.status).toBe(status)
+      }
+
+      if (content) {
+        expect(await res.text()).toMatch(content)
+      }
+    }
+  )
+
   it('should successfully rewrite a WebSocket request', async () => {
     // TODO: remove once test failure has been fixed
     if (isTurbo) return
@@ -1534,6 +1572,7 @@ const runTests = (isDev = false, isTurbo = false) => {
       expect(manifest).toEqual({
         version: 3,
         pages404: true,
+        caseSensitive: true,
         basePath: '',
         dataRoutes: [
           {

test/integration/dynamic-routing/test/index.test.js

@@ -1232,6 +1232,7 @@ function runTests({ dev }) {
       expect(manifest).toEqual({
         version: 3,
         pages404: true,
+        caseSensitive: false,
         basePath: '',
         headers: [],
         rewrites: [],

test/lib/next-test-utils.js

@@ -154,7 +154,7 @@ export function renderViaHTTP(appPort, pathname, query, opts) {
  * @param {string} pathname
  * @param {Record<string, any> | string | null | undefined} [query]
  * @param {import('node-fetch').RequestInit} [opts]
- * @returns {Promise<Response & {buffer: any} & {headers: any}>}
+ * @returns {Promise<Response & {buffer: any} & {headers: Headers}>}
  */
 export function fetchViaHTTP(appPort, pathname, query, opts) {
   const url = query ? withQuery(pathname, query) : pathname