saga-middleware-example

handler404.js

import {Base404Error, Order404} from './exceptions.js'

import './order404.tag.html'
import './page404.tag.html'

export const handler = func => function*(...args){
  try {
    return yield* func(...args)
  } catch(error) {
    if (!(error instanceof Base404Error))
      throw error

    if (error instanceof Order404){
      riot.mount('#page-container', 'pages-order404', {error})
      return
    }

    riot.mount('#page-container', 'pages-page404', {error}) // универсальная заглушка на все случаи жизни
  }
}

redirectsMiddleware.js

import {go2page} from '../../helpers' // its a legacy code

import * as exceptions from './exceptions.js'

export const handler = saga => function*(...args){
  try {
    let result = yield* saga(...args)

    if (result instanceof exceptions.Redirect2URL)
      throw result

    return result
  } catch(error) {
    if (error instanceof exceptions.Redirect2URL){
      let {compoundURL, title, shouldReplace} = error.destination
      _.defer(()=>{
        // TODO window.history.pushState
      })
    } else
      throw error
  }
}

router.js

// ....
// внутри takeLatest мы уже знаем какую pageSaga нужно запустить
let wrappedPageSaga = showPlugIfFailure(
  redirectsHandler.handler(
    handler404.handler(
      handleAPIAuthErrors.handler(pageSaga)
    )
  )
)
yield* wrappedPageSaga
// ...

showPlugIfFailureMiddleware.js

import failure_plug_saga from './pages/failure_plug'

const showPlugIfFailure = saga => function*(...args){
  try {
    return yield* saga(...args)
  } catch(exception) {
    Raven.captureException(exception)
    return yield* failure_plug_saga(...args, exception)
  }
}