Add codemod for middleware to proxy (#84127)

Stacked to #84119

This PR adds a codemod for renaming `middleware` to `proxy`. Below are
the behaviors:

- Rename `middleware.*`, `src/middleware.*` to `proxy.*`, `src/proxy.*`
- Rename function/variable exports from `middleware` to `proxy`. Default
exports are skipped.

Author: devjiwonchoi

packages/next-codemod/lib/utils.ts

@@ -121,4 +121,9 @@ export const TRANSFORMER_INQUIRER_CHOICES = [
     value: 'next-lint-to-eslint-cli',
     version: '16.0.0',
   },
+  {
+    title: 'Migrate from deprecated `middleware` convention to `proxy`',
+    value: 'middleware-to-proxy',
+    version: '16.0.0',
+  },
 ]

packages/next-codemod/transforms/__testfixtures__/middleware-to-proxy/async-function.input.ts

@@ -0,0 +1,10 @@
+import { NextResponse, NextRequest } from 'next/server'
+
+export async function middleware(request: NextRequest) {
+  const response = await fetch('/api/auth')
+  return NextResponse.redirect(new URL('/home', request.url))
+}
+
+export const config = {
+  matcher: '/about/:path*',
+}

packages/next-codemod/transforms/__testfixtures__/middleware-to-proxy/async-function.output.ts

@@ -0,0 +1,10 @@
+import { NextResponse, NextRequest } from 'next/server'
+
+export async function proxy(request: NextRequest) {
+  const response = await fetch('/api/auth')
+  return NextResponse.redirect(new URL('/home', request.url))
+}
+
+export const config = {
+  matcher: '/about/:path*',
+}

packages/next-codemod/transforms/__testfixtures__/middleware-to-proxy/const-export.input.ts

@@ -0,0 +1,11 @@
+import { NextResponse, NextRequest } from 'next/server'
+
+const middleware = (request: NextRequest) => {
+  return NextResponse.redirect(new URL('/home', request.url))
+}
+
+export { middleware }
+
+export const config = {
+  matcher: '/about/:path*',
+}

packages/next-codemod/transforms/__testfixtures__/middleware-to-proxy/const-export.output.ts

@@ -0,0 +1,11 @@
+import { NextResponse, NextRequest } from 'next/server'
+
+const proxy = (request: NextRequest) => {
+  return NextResponse.redirect(new URL('/home', request.url))
+}
+
+export { proxy }
+
+export const config = {
+  matcher: '/about/:path*',
+}

packages/next-codemod/transforms/__testfixtures__/middleware-to-proxy/default-export.input.ts

@@ -0,0 +1,9 @@
+import { NextResponse, NextRequest } from 'next/server'
+
+export default function middleware(request: NextRequest) {
+  return NextResponse.redirect(new URL('/home', request.url))
+}
+
+export const config = {
+  matcher: '/about/:path*',
+}

packages/next-codemod/transforms/__testfixtures__/middleware-to-proxy/default-export.output.ts

@@ -0,0 +1,9 @@
+import { NextResponse, NextRequest } from 'next/server'
+
+export default function proxy(request: NextRequest) {
+  return NextResponse.redirect(new URL('/home', request.url))
+}
+
+export const config = {
+  matcher: '/about/:path*',
+}

packages/next-codemod/transforms/__testfixtures__/middleware-to-proxy/export-as-alias.input.ts

@@ -0,0 +1,9 @@
+import { NextResponse } from 'next/server'
+
+const proxy = 'existing proxy variable'
+
+function middleware() {
+  return NextResponse.next()
+}
+
+export { middleware as randomName }

packages/next-codemod/transforms/__testfixtures__/middleware-to-proxy/export-as-alias.output.ts

@@ -0,0 +1,9 @@
+import { NextResponse } from 'next/server'
+
+const proxy = 'existing proxy variable'
+
+function _proxy1() {
+  return NextResponse.next()
+}
+
+export { _proxy1 as randomName }

packages/next-codemod/transforms/__testfixtures__/middleware-to-proxy/export-specifier.input.ts

@@ -0,0 +1,11 @@
+import { NextResponse, NextRequest } from 'next/server'
+
+function middleware(request: NextRequest) {
+  return NextResponse.redirect(new URL('/home', request.url))
+}
+
+const config = {
+  matcher: '/about/:path*',
+}
+
+export { middleware, config }