error.js

import { warn } from 'shared/util'
import { findAllInstances } from './find'

function errorHandler (errorOrString, vm) {
  const error =
    typeof errorOrString === 'object'
      ? errorOrString
      : new Error(errorOrString)

  vm._error = error
  throw error
}

export function throwIfInstancesThrew (vm) {
  const instancesWithError = findAllInstances(vm).filter(
    _vm => _vm._error
  )

  if (instancesWithError.length > 0) {
    throw instancesWithError[0]._error
  }
}

let hasWarned = false

// Vue swallows errors thrown by instances, even if the global error handler
// throws. In order to throw in the test, we add an _error property to an
// instance when it throws. Then we loop through the instances with
// throwIfInstancesThrew and throw an error in the test context if any
// instances threw.
export function addGlobalErrorHandler (_Vue) {
  const existingErrorHandler = _Vue.config.errorHandler

  if (existingErrorHandler === errorHandler) {
    return
  }

  if (_Vue.config.errorHandler && !hasWarned) {
    warn(
      `Global error handler detected (Vue.config.errorHandler). \n` +
      `Vue Test Utils sets a custom error handler to throw errors ` +
      `thrown by instances. If you want this behavior in ` +
      `your tests, you must remove the global error handler.`
    )
    hasWarned = true
  } else {
    _Vue.config.errorHandler = errorHandler
  }
}