chore: refactor header control

Author: orinokai

src/helpers/headers.ts

@@ -1,3 +1,4 @@
+import type { HandlerEvent } from '@netlify/functions'
 import type { NextConfigComplete } from 'next/dist/server/config-shared.js'
 
 export interface NetlifyVaryHeaderBuilder {
@@ -42,12 +43,7 @@ const removeSMaxAgeAndStaleWhileRevalidate = (headerValue: string): string =>
     })
     .join(`,`)
 
-export const handleVary = (
-  headers: Record<string, string>,
-  eventPath: string,
-  basePath: string,
-  autoDetectedLocales: string[],
-) => {
+export const handleVary = (headers: Record<string, string>, event: HandlerEvent, nextConfig: NextConfigComplete) => {
   const netlifyVaryBuilder: NetlifyVaryHeaderBuilder = {
     headers: [],
     languages: [],
@@ -58,8 +54,13 @@ export const handleVary = (
     netlifyVaryBuilder.headers.push(...getDirectives(headers.vary))
   }
 
+  const autoDetectedLocales = getAutoDetectedLocales(nextConfig)
+
   if (autoDetectedLocales.length > 1) {
-    const logicalPath = basePath && eventPath.startsWith(basePath) ? eventPath.slice(basePath.length) : eventPath
+    const logicalPath =
+      nextConfig.basePath && event.path.startsWith(nextConfig.basePath)
+        ? event.path.slice(nextConfig.basePath.length)
+        : event.path
 
     if (logicalPath === `/`) {
       netlifyVaryBuilder.languages.push(...autoDetectedLocales)

src/templates/server-handler.ts

@@ -6,18 +6,18 @@ import type { Handler, HandlerContext, HandlerEvent } from '@netlify/functions'
 import { Bridge } from '@vercel/node-bridge/bridge.js'
 import type { NextConfigComplete } from 'next/dist/server/config-shared.js'
 
-import { getAutoDetectedLocales, handleCacheControl, handleVary } from '../helpers/headers.js'
+import { handleCacheControl, handleVary } from '../helpers/headers.js'
 
 const require = createRequire(import.meta.url)
 
+/* these dependencies are generated during the build */
+// eslint-disable-next-line import/order
 const { getRequestHandlers } = require('next/dist/server/lib/start-server.js')
-
 const requiredServerFiles = require('../../.next/required-server-files.json')
 
 process.env.__NEXT_PRIVATE_STANDALONE_CONFIG = JSON.stringify(requiredServerFiles.config)
 
 const nextConfig = requiredServerFiles.config as NextConfigComplete
-const autoDetectedLocales = getAutoDetectedLocales(nextConfig)
 
 const __dirname = fileURLToPath(new URL('../..', import.meta.url))
 
@@ -60,7 +60,7 @@ export const handler: Handler = async function (event: HandlerEvent, context: Ha
   console.log('Next server response:', JSON.stringify(response, null, 2))
 
   handleCacheControl(headers)
-  handleVary(headers, event.path, nextConfig.basePath, autoDetectedLocales)
+  handleVary(headers, event, nextConfig)
 
   return {
     ...result,