fix: fall back to default value when `publicPath` is falsy (#4365)

* test: let tests fail

* fix: add falsy default fallback

* fix(publicPath): force adding trailing slash

* fix: also change _publicPath

packages/config/src/options.js

@@ -5,7 +5,7 @@ import defaults from 'lodash/defaults'
 import pick from 'lodash/pick'
 import isObject from 'lodash/isObject'
 import consola from 'consola'
-import { isPureObject, isUrl, guardDir, isNonEmptyString } from '@nuxt/common'
+import { guardDir, isNonEmptyString, isPureObject, isUrl } from '@nuxt/common'
 import { getDefaultNuxtConfig } from './config'
 
 export function getNuxtConfig(_options) {
@@ -53,7 +53,14 @@ export function getNuxtConfig(_options) {
 
   // Apply defaults
   const nuxtConfig = getDefaultNuxtConfig()
+
   nuxtConfig.build._publicPath = nuxtConfig.build.publicPath
+
+  // Fall back to default if publicPath is falsy
+  if (options.build && !options.build.publicPath) {
+    options.build.publicPath = undefined
+  }
+
   defaultsDeep(options, nuxtConfig)
 
   // Check srcDir and generate.dir excistence
@@ -111,6 +118,9 @@ export function getNuxtConfig(_options) {
     options.appTemplatePath = path.resolve(options.srcDir, options.appTemplatePath)
   }
 
+  options.build.publicPath = options.build.publicPath.replace(/([^/])$/, '$1/')
+  options.build._publicPath = options.build._publicPath.replace(/([^/])$/, '$1/')
+
   // Ignore publicPath on dev
   /* istanbul ignore if */
   if (options.dev && isUrl(options.build.publicPath)) {

test/fixtures/basic/nuxt.config.js

@@ -70,6 +70,7 @@ export default {
   ],
   build: {
     scopeHoisting: true,
+    publicPath: '',
     postcss: {
       preset: {
         features: {