fix: normalise basepath (#228)

* fix: normalise redirect/rewrite target locales

* chore: fix data urls

* fix: normalise basepath

---------

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

Author: ascorbic

edge-runtime/lib/next-request.ts

@@ -1,6 +1,6 @@
 import type { Context } from '@netlify/edge-functions'
 
-import { normalizeDataUrl, removeBasePath, normalizeLocalePath } from './util.ts'
+import { normalizeDataUrl, removeBasePath, normalizeLocalePath, addBasePath } from './util.ts'
 
 interface I18NConfig {
   defaultLocale: string
@@ -41,6 +41,7 @@ const normalizeRequestURL = (
   const url = new URL(originalURL)
 
   url.pathname = removeBasePath(url.pathname, nextConfig?.basePath)
+  const didRemoveBasePath = url.toString() !== originalURL
 
   let detectedLocale: string | undefined
 
@@ -64,6 +65,10 @@ const normalizeRequestURL = (
     url.pathname = `${url.pathname}/`
   }
 
+  if (didRemoveBasePath) {
+    url.pathname = addBasePath(url.pathname, nextConfig?.basePath)
+  }
+
   return {
     url: url.toString(),
     detectedLocale,

edge-runtime/lib/response.ts

@@ -3,7 +3,13 @@ import { HTMLRewriter } from '../vendor/deno.land/x/[email protected]/
 
 import { updateModifiedHeaders } from './headers.ts'
 import type { StructuredLogger } from './logging.ts'
-import { normalizeDataUrl, normalizeLocalePath, relativizeURL, rewriteDataPath } from './util.ts'
+import {
+  addBasePath,
+  normalizeDataUrl,
+  normalizeLocalePath,
+  relativizeURL,
+  rewriteDataPath,
+} from './util.ts'
 import { addMiddlewareHeaders, isMiddlewareRequest, isMiddlewareResponse } from './middleware.ts'
 import { RequestData } from './next-request.ts'
 
@@ -237,9 +243,9 @@ function normalizeLocalizedTarget({
     !normalizedTarget.pathname.startsWith(`/api/`) &&
     !normalizedTarget.pathname.startsWith(`/_next/static/`)
   ) {
-    targetUrl.pathname = `/${locale}${normalizedTarget.pathname}`
-    return targetUrl.toString()
+    targetUrl.pathname = addBasePath(`/${locale}${normalizedTarget.pathname}`, nextConfig?.basePath)
+  } else {
+    targetUrl.pathname = addBasePath(normalizedTarget.pathname, nextConfig?.basePath)
   }
-  targetUrl.pathname = normalizedTarget.pathname
   return targetUrl.toString()
 }

edge-runtime/lib/util.ts

@@ -24,6 +24,13 @@ export const removeBasePath = (path: string, basePath?: string) => {
   return path
 }
 
+export const addBasePath = (path: string, basePath?: string) => {
+  if (basePath && !path.startsWith(basePath)) {
+    return `${basePath}${path}`
+  }
+  return path
+}
+
 // https://github.com/vercel/next.js/blob/canary/packages/next/src/shared/lib/i18n/normalize-locale-path.ts
 
 export interface PathLocale {
@@ -91,8 +98,11 @@ export function rewriteDataPath({
 }) {
   const normalizedDataUrl = normalizeDataUrl(removeBasePath(dataUrl, basePath))
 
-  return dataUrl.replace(
-    normalizeIndex(normalizedDataUrl),
-    stripTrailingSlash(normalizeIndex(newRoute)),
+  return addBasePath(
+    dataUrl.replace(
+      normalizeIndex(normalizedDataUrl),
+      stripTrailingSlash(normalizeIndex(newRoute)),
+    ),
+    basePath,
   )
 }