Function applySingletonAppMutations

packages/runtime-core/src/compat/global.ts:390–426

(app: App)

}

function applySingletonAppMutations(app: App) {
  // copy over asset registries and deopt flag
  app._context.mixins = [...singletonApp._context.mixins]
  ;['components', 'directives', 'filters'].forEach(key => {
    // @ts-expect-error
    app._context[key] = Object.create(singletonApp._context[key])
  })

  // copy over global config mutations
  isCopyingConfig = true
  for (const key in singletonApp.config) {
    if (key === 'isNativeTag') continue
    if (
      isRuntimeOnly() &&
      (key === 'isCustomElement' || key === 'compilerOptions')
    ) {
      continue
    }
    const val = singletonApp.config[key as keyof AppConfig]
    // @ts-expect-error
    app.config[key] = isObject(val) ? Object.create(val) : val

    // compat for runtime ignoredElements -> isCustomElement
    if (
      key === 'ignoredElements' &&
      isCompatEnabled(DeprecationTypes.CONFIG_IGNORED_ELEMENTS, null) &&
      !isRuntimeOnly() &&
      isArray(val)
    ) {
      app.config.compilerOptions.isCustomElement = tag => {
        return val.some(v => (isString(v) ? v === tag : v.test(tag)))
      }
    }
  }
  isCopyingConfig = false
  applySingletonPrototype(app, singletonCtor)
}

function applySingletonPrototype(app: App, Ctor: Function) {
  // copy prototype augmentations as config.globalProperties