fix: correctly handle matchers with lookaheads and i18n (#1693)

* fix: correctly handle matchers with lookaheads and i18n

* chore: add tests

* fix: add back rest of matcher

* chore: remove comment

Author: ascorbic

cypress/integration/middleware/enhanced.spec.ts

@@ -18,7 +18,7 @@ describe('Enhanced middleware', () => {
   })
 
   it('modifies the page props', () => {
-    cy.request('/_next/data/build-id/static.json').then((response) => {
+    cy.request('/_next/data/build-id/en/static.json').then((response) => {
       expect(response.body).to.have.nested.property('pageProps.showAd', true)
       expect(response.body)
         .to.have.nested.property('pageProps.message')

cypress/integration/middleware/standard.spec.ts

@@ -37,11 +37,22 @@ describe('Middleware matchers', () => {
   })
 
   it('matches when headers are sent', () => {
-    cy.request('/_next/data/build-id/static.json').then((response) => {
+    cy.request('/_next/data/build-id/en/static.json').then((response) => {
       expect(response.headers).to.have.property('x-is-deno', 'true')
       expect(response.headers).to.have.property('x-modified-edge', 'true')
     })
   })
+
+  it('correctly handles negative lookaheads', () => {
+    cy.request('/shows/11').then((response) => {
+      expect(response.headers).to.have.property('x-is-deno', 'true')
+      expect(response.headers).to.have.property('x-modified-edge', 'true')
+    })
+    cy.request('/shows/99').then((response) => {
+      expect(response.headers).not.to.have.property('x-is-deno', 'true')
+      expect(response.headers).not.to.have.property('x-modified-edge', 'true')
+    })
+  })
 })
 
 describe('Middleware with edge API', () => {

demos/middleware/middleware.ts

@@ -94,7 +94,7 @@ export const config = {
     '/api/:all*',
     '/headers',
     { source: '/static' },
-    { source: '/shows/:all*' },
+    { source: '/shows/((?!99|88).*)' },
     {
       source: '/conditional',
       has: [

demos/middleware/next.config.js

@@ -7,6 +7,10 @@ const nextConfig = {
     ignoreDuringBuilds: true,
   },
   generateBuildId: () => 'build-id',
+  i18n: {
+    defaultLocale: 'en',
+    locales: ['en'],
+  },
 }
 
 module.exports = nextConfig

package-lock.json

@@ -28,6 +28,7 @@
     "p-limit": "^3.1.0",
     "pathe": "^0.2.0",
     "pretty-bytes": "^5.6.0",
+    "regexp-tree": "^0.1.24",
     "semver": "^7.3.5",
     "slash": "^3.0.0",
     "tiny-glob": "^0.2.9"

packages/runtime/package.json

@@ -10,7 +10,8 @@ import type { MiddlewareManifest } from 'next/dist/build/webpack/plugins/middlew
 import type { RouteHas } from 'next/dist/lib/load-custom-routes'
 import { outdent } from 'outdent'
 
-import { getRequiredServerFiles } from './config'
+import { getRequiredServerFiles, NextConfig } from './config'
+import { makeLocaleOptional, stripLookahead } from './matchers'
 
 // This is the format as of next@12.2
 interface EdgeFunctionDefinitionV1 {
@@ -132,10 +133,12 @@ const writeEdgeFunction = async ({
   edgeFunctionDefinition,
   edgeFunctionRoot,
   netlifyConfig,
+  nextConfig,
 }: {
   edgeFunctionDefinition: EdgeFunctionDefinition
   edgeFunctionRoot: string
   netlifyConfig: NetlifyConfig
+  nextConfig: NextConfig
 }): Promise<
   Array<{
     function: string
@@ -165,14 +168,22 @@ const writeEdgeFunction = async ({
   // The v1 middleware manifest has a single regexp, but the v2 has an array of matchers
   if ('regexp' in edgeFunctionDefinition) {
     matchers.push({ regexp: edgeFunctionDefinition.regexp })
+  } else if (nextConfig.i18n) {
+    matchers.push(
+      ...edgeFunctionDefinition.matchers.map((matcher) => ({
+        ...matcher,
+        regexp: makeLocaleOptional(matcher.regexp),
+      })),
+    )
   } else {
     matchers.push(...edgeFunctionDefinition.matchers)
   }
+
   await writeJson(join(edgeFunctionDir, 'matchers.json'), matchers)
 
   // We add a defintion for each matching path
   return matchers.map((matcher) => {
-    const pattern = matcher.regexp
+    const pattern = stripLookahead(matcher.regexp)
     return { function: name, pattern, name: edgeFunctionDefinition.name }
   })
 }
@@ -258,6 +269,7 @@ export const writeEdgeFunctions = async (netlifyConfig: NetlifyConfig) => {
         edgeFunctionDefinition,
         edgeFunctionRoot,
         netlifyConfig,
+        nextConfig,
       })
       manifest.functions.push(...functionDefinitions)
     }
@@ -270,6 +282,7 @@ export const writeEdgeFunctions = async (netlifyConfig: NetlifyConfig) => {
           edgeFunctionDefinition,
           edgeFunctionRoot,
           netlifyConfig,
+          nextConfig,
         })
         manifest.functions.push(...functionDefinitions)
       }