feat(config): warn usage of non exist exprimental features

packages/next/server/config.ts

@@ -44,6 +44,24 @@ const experimentalWarning = execOnce(
  }
 )
 
+const notExistedExperimentalFeatureWarning = execOnce(
+ (configFileName: string, features: string[]) => {
+ const s = features.length > 1 ? 's' : ''
+ const dont = features.length > 1 ? 'do not' : 'does not'
+ const exist = features.length > 1 ? 'exist' : 'exists'
+ const them = features.length > 1 ? 'them' : 'it'
+ Log.warn(
+ chalk.bold(
+ `You have defined experimental feature${s} (${features.join(
+ ', '
+ )}) in ${configFileName} that ${dont} ${exist} in this version of Next.js.`
+ )
+ )
+ Log.warn(`Please remove ${them} from your configuration.`)
+ console.warn()
+ }
+)
+
 function assignDefaults(userConfig: { [key: string]: any }) {
  const configFileName = userConfig.configFileName
  if (typeof userConfig.exportTrailingSlash !== 'undefined') {
@@ -79,16 +97,29 @@ function assignDefaults(userConfig: { [key: string]: any }) {
  }
 
  if (key === 'experimental' && typeof value === 'object') {
- const enabledExperimentalFeatures = (
- Object.keys(value) as (keyof ExperimentalConfig)[]
- ).filter(
- // defaultConfig is pre-defined, thus defaultConfig.experimental can not be undefined
- (featureName) =>
+ const notExistedExperimentalFeatures: string[] = []
+ const enabledExperimentalFeatures: (keyof ExperimentalConfig)[] = []
+
+ for (const featureName of Object.keys(
+ value
+ ) as (keyof ExperimentalConfig)[]) {
+ if (!(featureName in defaultConfig.experimental!)) {
+ notExistedExperimentalFeatures.push(featureName)
+ } else if (
  value[featureName] !== defaultConfig.experimental![featureName]
- )
+ ) {
+ enabledExperimentalFeatures.push(featureName)
+ }
+ }
 
+ if (notExistedExperimentalFeatures.length > 0) {
+ notExistedExperimentalFeatureWarning(
+ configFileName,
+ notExistedExperimentalFeatures
+ )
+ }
  if (enabledExperimentalFeatures.length > 0) {
- experimentalWarning(configFileName, Object.keys(value))
+ experimentalWarning(configFileName, enabledExperimentalFeatures)
  }
  }