fix: basePath is undefined when a site has no config file

src/lib/helpers/convertToBasePathRedirects.js

@@ -3,7 +3,7 @@
 // NOTE: /withoutProps/redirects.js has some of its own contained basePath logic
 
 const getBasePathDefaultRedirects = ({ basePath, nextRedirects }) => {
-  if (basePath === '') return []
+  if (!basePath) return []
   // In a basePath-configured site, all _next assets are fetched with the prepended basePath
   return [
     {
@@ -16,7 +16,7 @@ const getBasePathDefaultRedirects = ({ basePath, nextRedirects }) => {
 }
 
 const convertToBasePathRedirects = ({ basePath, nextRedirects }) => {
-  if (basePath === '') return nextRedirects
+  if (!basePath) return nextRedirects
   const basePathRedirects = getBasePathDefaultRedirects({ basePath, nextRedirects })
   nextRedirects.forEach((r) => {
     if (r.route === '/') {

src/lib/helpers/formatRedirectTarget.js

@@ -2,7 +2,7 @@
 const { DYNAMIC_PARAMETER_REGEX } = require('../constants/regex')
 
 const formatRedirectTarget = ({ basePath, target }) =>
-  basePath !== '' && target.includes(basePath)
+  basePath && basePath !== '' && target.includes(basePath)
     ? target.replace(DYNAMIC_PARAMETER_REGEX, '/:$1').replace('[', '').replace(']', '').replace('...', '')
     : target
 

src/lib/pages/withoutProps/redirects.js

@@ -30,7 +30,7 @@ const getRedirects = async () => {
 
     // For sites that use basePath, manually add necessary redirects here specific
     // only to this page type (which excludes static route redirects by default)
-    if (basePath !== '') {
+    if (basePath && basePath !== '') {
       redirects.push({
         route: `${basePath}${route}`,
         target: route,

src/lib/steps/setupRedirects.js

@@ -48,7 +48,7 @@ const setupRedirects = async (publishPath) => {
   redirects.push('# Next-on-Netlify Redirects')
 
   const { basePath } = await getNextConfig()
-  if (basePath !== '') {
+  if (basePath && basePath !== '') {
     nextRedirects = convertToBasePathRedirects({ basePath, nextRedirects })
   }