chore: load next config depends on root publish build directory

Author: rayriffy

helpers/defaultFailBuild.js

@@ -0,0 +1,3 @@
+exports.defaultFailBuild = function (message, { error }) {
+  throw new Error(`${message}\n${error.stack}`)
+}

helpers/getNextConfig.js

@@ -2,26 +2,23 @@
 
 const { resolve } = require('path')
 
+const { defaultFailBuild } = require('./defaultFailBuild')
 const moize = require('moize')
 
 // Load next.config.js
-const getNextConfig = async function (failBuild = defaultFailBuild) {
+const getNextConfig = async function (failBuild = defaultFailBuild, publishPath = '.') {
   // We cannot load `next` at the top-level because we validate whether the
   // site is using `next` inside `onPreBuild`.
   const { PHASE_PRODUCTION_BUILD } = require('next/constants')
   const loadConfig = require('next/dist/next-server/server/config').default
 
   try {
-    return await loadConfig(PHASE_PRODUCTION_BUILD, resolve('.'))
+    return await loadConfig(PHASE_PRODUCTION_BUILD, resolve(publishPath))
   } catch (error) {
     return failBuild('Error loading your next.config.js.', { error })
   }
 }
 
 const moizedGetNextConfig = moize(getNextConfig, { maxSize: 1e3, isPromise: true })
 
-const defaultFailBuild = function (message, { error }) {
-  throw new Error(`${message}\n${error.stack}`)
-}
-
 module.exports = moizedGetNextConfig

src/lib/helpers/getNextDistDir.js

@@ -1,9 +1,11 @@
 // Get the NextJS distDir specified in next.config.js
 const { join } = require('path')
+
 const getNextConfig = require('../../../helpers/getNextConfig')
+const { defaultFailBuild } = require('../../../helpers/defaultFailBuild')
 
-const getNextDistDir = async () => {
-  const nextConfig = await getNextConfig()
+const getNextDistDir = async (publishPath) => {
+  const nextConfig = await getNextConfig(defaultFailBuild, publishPath)
 
   return join('.', nextConfig.distDir)
 }

src/lib/steps/copyNextAssets.js

@@ -6,7 +6,7 @@ const getNextDistDir = require('../helpers/getNextDistDir')
 // Copy the NextJS' static assets from NextJS distDir to Netlify publish folder.
 // These need to be available for NextJS to work.
 const copyNextAssets = async (publishPath) => {
-  const nextDistDir = await getNextDistDir()
+  const nextDistDir = await getNextDistDir(publishPath)
   const staticAssetsPath = join(nextDistDir, 'static')
   if (!existsSync(staticAssetsPath)) {
     throw new Error(