Remove mitt and use an internal EventEmitter (#2477)

This fixes one of the crucial bug in Next.js
The issue happens when you try to load a page when it's
prefetching.
With mitt, it only fires the first registered event.

client/index.js

 import { createElement } from 'react'
 import ReactDOM from 'react-dom'
-import mitt from 'mitt'
 import HeadManager from './head-manager'
 import { createRouter } from '../lib/router'
+import EventEmitter from '../lib/EventEmitter'
 import App from '../lib/app'
 import { loadGetInitialProps, getURL } from '../lib/utils'
 import ErrorDebugComponent from '../lib/error-debug'
@@ -77,7 +77,7 @@ export default async () => {
     err
   })
 
-  const emitter = mitt()
+  const emitter = new EventEmitter()
 
   router.subscribe(({ Component, props, hash, err }) => {
     render({ Component, props, err, hash, emitter })

lib/EventEmitter.js

+export default class EventEmitter {
+  listeners = {}
+
+  on (event, cb) {
+    if (!this.listeners[event]) {
+      this.listeners[event] = new Set()
+    }
+
+    this.listeners[event].add(cb)
+  }
+
+  emit (event, ...data) {
+    if (!this.listeners[event]) return
+    this.listeners[event].forEach(cb => cb(...data))
+  }
+
+  off (event, cb) {
+    if (!this.listeners[event]) return
+    this.listeners[event].delete(cb)
+  }
+}

lib/page-loader.js

 /* global window, document, __NEXT_DATA__ */
-import mitt from 'mitt'
+import EventEmitter from './EventEmitter'
 
 const webpackModule = module
 
@@ -10,10 +10,10 @@ export default class PageLoader {
 
     this.pageCache = {}
     this.pageLoadedHandlers = {}
-    this.pageRegisterEvents = mitt()
+    this.pageRegisterEvents = new EventEmitter()
     this.loadingRoutes = {}
 
-    this.chunkRegisterEvents = mitt()
+    this.chunkRegisterEvents = new EventEmitter()
     this.loadedChunks = {}
   }
 

lib/router/router.js

 /* global __NEXT_DATA__ */
 
 import { parse, format } from 'url'
-import mitt from 'mitt'
+import EventEmitter from '../EventEmitter'
 import shallowEquals from '../shallow-equals'
 import PQueue from '../p-queue'
 import { loadGetInitialProps, getURL } from '../utils'
@@ -22,7 +22,7 @@ export default class Router {
     }
 
     // Handling Router Events
-    this.events = mitt()
+    this.events = new EventEmitter()
 
     this.pageLoader = pageLoader
     this.prefetchQueue = new PQueue({ concurrency: 2 })

package.json

@@ -77,7 +77,6 @@
     "loader-utils": "1.1.0",
     "md5-file": "3.1.1",
     "minimist": "1.2.0",
-    "mitt": "1.1.2",
     "mkdirp-then": "1.2.0",
     "mv": "2.1.1",
     "mz": "2.6.0",

yarn.lock

@@ -71,8 +71,8 @@ acorn@^4.0.3, acorn@^4.0.4:
   resolved "https://registry.yarnpkg.com/acorn/-/acorn-4.0.13.tgz#105495ae5361d697bd195c825192e1ad7f253787"
 
 acorn@^5.0.0, acorn@^5.0.1:
-  version "5.0.3"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.0.3.tgz#c460df08491463f028ccb82eab3730bf01087b3d"
+  version "5.1.0"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-5.1.0.tgz#e468bf609b0672700e02f878ae2f1b360fe24b4f"
 
 ajv-keywords@^1.0.0:
   version "1.5.1"
@@ -210,8 +210,8 @@ arr-diff@^2.0.0:
     arr-flatten "^1.0.1"
 
 arr-flatten@^1.0.1:
-  version "1.0.3"
-  resolved "https://registry.yarnpkg.com/arr-flatten/-/arr-flatten-1.0.3.tgz#a274ed85ac08849b6bd7847c4580745dc51adfb1"
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/arr-flatten/-/arr-flatten-1.1.0.tgz#36048bbff4e7b47e136644316c99669ea5ae91f1"
 
 array-differ@^1.0.0:
   version "1.0.0"
@@ -823,9 +823,9 @@ babel-plugin-transform-strict-mode@^6.24.1:
     babel-runtime "^6.22.0"
     babel-types "^6.24.1"
 
-babel-preset-env@1.5.2:
-  version "1.5.2"
-  resolved "https://registry.yarnpkg.com/babel-preset-env/-/babel-preset-env-1.5.2.tgz#cd4ae90a6e94b709f97374b33e5f8b983556adef"
+babel-preset-env@1.6.0:
+  version "1.6.0"
+  resolved "https://registry.yarnpkg.com/babel-preset-env/-/babel-preset-env-1.6.0.tgz#2de1c782a780a0a5d605d199c957596da43c44e4"
   dependencies:
     babel-plugin-check-es2015-constants "^6.22.0"
     babel-plugin-syntax-trailing-function-commas "^6.22.0"
@@ -1206,8 +1206,8 @@ camelcase@^4.1.0:
   resolved "https://registry.yarnpkg.com/camelcase/-/camelcase-4.1.0.tgz#d545635be1e33c542649c69173e5de6acfae34dd"
 
 caniuse-lite@^1.0.30000684:
-  version "1.0.30000694"
-  resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30000694.tgz#1492dab7c10c608c9d37a723e6e3e7873e0ce94f"
+  version "1.0.30000697"
+  resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30000697.tgz#125fb00604b63fbb188db96a667ce2922dcd6cdd"
 
 case-sensitive-paths-webpack-plugin@2.1.1:
   version "2.1.1"
@@ -1364,10 +1364,8 @@ combined-stream@^1.0.5, combined-stream@~1.0.5:
     delayed-stream "~1.0.0"
 
 commander@^2.9.0:
-  version "2.10.0"
-  resolved "https://registry.yarnpkg.com/commander/-/commander-2.10.0.tgz#e1f5d3245de246d1a5ca04702fa1ad1bd7e405fe"
-  dependencies:
-    graceful-readlink ">= 1.0.0"
+  version "2.11.0"
+  resolved "https://registry.yarnpkg.com/commander/-/commander-2.11.0.tgz#157152fd1e7a6c8d98a5b715cf376df928004563"
 
 commondir@^1.0.1:
   version "1.0.1"
@@ -1420,11 +1418,11 @@ content-type@~1.0.2:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/content-type/-/content-type-1.0.2.tgz#b7d113aee7a8dd27bd21133c4dc2529df1721eed"
 
-convert-source-map@1.3.0, convert-source-map@^1.1.0, convert-source-map@^1.3.0:
+convert-source-map@1.3.0:
   version "1.3.0"
   resolved "https://registry.yarnpkg.com/convert-source-map/-/convert-source-map-1.3.0.tgz#e9f3e9c6e2728efc2676696a70eb382f73106a67"
 
-convert-source-map@^1.4.0:
+convert-source-map@^1.1.0, convert-source-map@^1.3.0, convert-source-map@^1.4.0:
   version "1.5.0"
   resolved "https://registry.yarnpkg.com/convert-source-map/-/convert-source-map-1.5.0.tgz#9acd70851c6d5dfdd93d9282e5edf94a03ff46b5"
 
@@ -1718,8 +1716,8 @@ detect-indent@^4.0.0:
     repeating "^2.0.0"
 
 diff@^3.2.0:
-  version "3.2.0"
-  resolved "https://registry.yarnpkg.com/diff/-/diff-3.2.0.tgz#c9ce393a4b7cbd0b058a725c93df299027868ff9"
+  version "3.3.0"
+  resolved "https://registry.yarnpkg.com/diff/-/diff-3.3.0.tgz#056695150d7aa93237ca7e378ac3b1682b7963b9"
 
 diffie-hellman@^5.0.0:
   version "5.0.2"
@@ -1790,8 +1788,8 @@ ee-first@1.1.1:
   resolved "https://registry.yarnpkg.com/ee-first/-/ee-first-1.1.1.tgz#590c61156b0ae2f4f0255732a158b266bc56b21d"
 
 electron-to-chromium@^1.3.14:
-  version "1.3.14"
-  resolved "https://registry.yarnpkg.com/electron-to-chromium/-/electron-to-chromium-1.3.14.tgz#64af0f9efd3c3c6acd57d71f83b49ca7ee9c4b43"
+  version "1.3.15"
+  resolved "https://registry.yarnpkg.com/electron-to-chromium/-/electron-to-chromium-1.3.15.tgz#08397934891cbcfaebbd18b82a95b5a481138369"
 
 elegant-spinner@^1.0.1:
   version "1.0.1"
@@ -1834,8 +1832,8 @@ end-of-stream@^1.0.0:
     once "^1.4.0"
 
 enhanced-resolve@^3.0.0:
-  version "3.1.0"
-  resolved "https://registry.yarnpkg.com/enhanced-resolve/-/enhanced-resolve-3.1.0.tgz#9f4b626f577245edcf4b2ad83d86e17f4f421dec"
+  version "3.3.0"
+  resolved "https://registry.yarnpkg.com/enhanced-resolve/-/enhanced-resolve-3.3.0.tgz#950964ecc7f0332a42321b673b38dc8ff15535b3"
   dependencies:
     graceful-fs "^4.1.2"
     memory-fs "^0.4.0"
@@ -1846,7 +1844,7 @@ entities@^1.1.1, entities@~1.1.1:
   version "1.1.1"
   resolved "https://registry.yarnpkg.com/entities/-/entities-1.1.1.tgz#6e5c2d0a5621b5dadaecef80b90edfb5cd7772f0"
 
-"errno@>=0.1.1 <0.2.0-0", errno@^0.1.2, errno@^0.1.3:
+errno@^0.1.2, errno@^0.1.3, errno@^0.1.4:
   version "0.1.4"
   resolved "https://registry.yarnpkg.com/errno/-/errno-0.1.4.tgz#b896e23a9e5e8ba33871fc996abd3635fc9a1c7d"
   dependencies:
@@ -2307,8 +2305,8 @@ find-cache-dir@^1.0.0:
     pkg-dir "^2.0.0"
 
 find-root@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/find-root/-/find-root-1.0.0.tgz#962ff211aab25c6520feeeb8d6287f8f6e95807a"
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/find-root/-/find-root-1.1.0.tgz#abcfc8ba76f708c42a97b3d685b7e9450bfb9ce4"
 
 find-up@^1.0.0:
   version "1.1.2"
@@ -2486,7 +2484,7 @@ glob-promise@3.1.0:
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/glob-promise/-/glob-promise-3.1.0.tgz#198882a3817be7dc2c55f92623aa9e7b3f82d1eb"
 
-glob@7.1.1, glob@^7.1.1:
+glob@7.1.1, glob@^7.0.6, glob@^7.1.1:
   version "7.1.1"
   resolved "https://registry.yarnpkg.com/glob/-/glob-7.1.1.tgz#805211df04faaf1c63a3600306cdf5ade50b2ec8"
   dependencies:
@@ -2507,7 +2505,7 @@ glob@^6.0.1:
     once "^1.3.0"
     path-is-absolute "^1.0.0"
 
-glob@^7.0.0, glob@^7.0.3, glob@^7.0.5, glob@^7.0.6, glob@^7.1.2:
+glob@^7.0.0, glob@^7.0.3, glob@^7.0.5, glob@^7.1.2:
   version "7.1.2"
   resolved "https://registry.yarnpkg.com/glob/-/glob-7.1.2.tgz#c19c9df9a028702d678612384a6552404c636d15"
   dependencies:
@@ -2554,10 +2552,6 @@ graceful-fs@^4.1.0, graceful-fs@^4.1.11, graceful-fs@^4.1.2, graceful-fs@^4.1.4:
   version "4.1.11"
   resolved "https://registry.yarnpkg.com/graceful-fs/-/graceful-fs-4.1.11.tgz#0e8bdfe4d1ddb8854d64e04ea7c00e2a026e5658"
 
-"graceful-readlink@>= 1.0.0":
-  version "1.0.1"
-  resolved "https://registry.yarnpkg.com/graceful-readlink/-/graceful-readlink-1.0.1.tgz#4cafad76bc62f02fa039b2f94e9a3dd3a391a725"
-
 growly@^1.3.0:
   version "1.3.0"
   resolved "https://registry.yarnpkg.com/growly/-/growly-1.3.0.tgz#f10748cbe76af964b7c96c93c6bcc28af120c081"
@@ -2619,8 +2613,8 @@ hash-base@^2.0.0:
     inherits "^2.0.1"
 
 hash.js@^1.0.0, hash.js@^1.0.3:
-  version "1.1.1"
-  resolved "https://registry.yarnpkg.com/hash.js/-/hash.js-1.1.1.tgz#5cb2e796499224e69fd0b00ed01d2d4a16e7a323"
+  version "1.1.3"
+  resolved "https://registry.yarnpkg.com/hash.js/-/hash.js-1.1.3.tgz#340dedbe6290187151c1ea1d777a3448935df846"
   dependencies:
     inherits "^2.0.3"
     minimalistic-assert "^1.0.0"
@@ -2654,8 +2648,8 @@ home-or-tmp@^2.0.0:
     os-tmpdir "^1.0.1"
 
 hosted-git-info@^2.1.4:
-  version "2.4.2"
-  resolved "https://registry.yarnpkg.com/hosted-git-info/-/hosted-git-info-2.4.2.tgz#0076b9f46a270506ddbaaea56496897460612a67"
+  version "2.5.0"
+  resolved "https://registry.yarnpkg.com/hosted-git-info/-/hosted-git-info-2.5.0.tgz#6d60e34b3abbc8313062c3b798ef8d901a07af3c"
 
 html-encoding-sniffer@^1.0.1:
   version "1.0.1"
@@ -2714,9 +2708,9 @@ https-browserify@0.0.1:
   version "0.0.1"
   resolved "https://registry.yarnpkg.com/https-browserify/-/https-browserify-0.0.1.tgz#3f91365cabe60b77ed0ebba24b454e3e09d95a82"
 
-husky@0.14.2:
-  version "0.14.2"
-  resolved "https://registry.yarnpkg.com/husky/-/husky-0.14.2.tgz#6df06483965d2254db95dd143c445d6d8509b4b8"
+husky@0.14.3:
+  version "0.14.3"
+  resolved "https://registry.yarnpkg.com/husky/-/husky-0.14.3.tgz#c69ed74e2d2779769a17ba8399b54ce0b63c12c3"
   dependencies:
     is-ci "^1.0.10"
     normalize-path "^1.0.0"
@@ -3268,8 +3262,8 @@ jest-validate@^20.0.3:
     pretty-format "^20.0.3"
 
 js-tokens@^3.0.0:
-  version "3.0.1"
-  resolved "https://registry.yarnpkg.com/js-tokens/-/js-tokens-3.0.1.tgz#08e9f132484a2c45a30907e9dc4d5567b7f114d7"
+  version "3.0.2"
+  resolved "https://registry.yarnpkg.com/js-tokens/-/js-tokens-3.0.2.tgz#9866df395102130e38f7f996bceb65443209c25b"
 
 js-yaml@3.6.1:
   version "3.6.1"
@@ -3753,10 +3747,6 @@ minimist@1.2.0, minimist@^1.1.0, minimist@^1.1.1, minimist@^1.2.0:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/minimist/-/minimist-1.2.0.tgz#a35008b20f41383eec1fb914f4cd5df79a264284"
 
-mitt@1.1.2:
-  version "1.1.2"
-  resolved "https://registry.yarnpkg.com/mitt/-/mitt-1.1.2.tgz#380e61480d6a615b660f07abb60d51e0a4e4bed6"
-
 mk-dirs@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/mk-dirs/-/mk-dirs-1.0.0.tgz#44ee67f82341c6762718e88e85e577882e1f67fd"
@@ -3912,8 +3902,8 @@ nopt@~1.0.10:
     abbrev "1"
 
 normalize-package-data@^2.3.2:
-  version "2.3.8"
-  resolved "https://registry.yarnpkg.com/normalize-package-data/-/normalize-package-data-2.3.8.tgz#d819eda2a9dedbd1ffa563ea4071d936782295bb"
+  version "2.4.0"
+  resolved "https://registry.yarnpkg.com/normalize-package-data/-/normalize-package-data-2.4.0.tgz#12f95a307d58352075a04907b84ac8be98ac012f"
   dependencies:
     hosted-git-info "^2.1.4"
     is-builtin-module "^1.0.0"
@@ -3951,8 +3941,8 @@ npm-which@^3.0.1:
     which "^1.2.10"
 
 npmlog@^4.0.2:
-  version "4.1.0"
-  resolved "https://registry.yarnpkg.com/npmlog/-/npmlog-4.1.0.tgz#dc59bee85f64f00ed424efb2af0783df25d1c0b5"
+  version "4.1.2"
+  resolved "https://registry.yarnpkg.com/npmlog/-/npmlog-4.1.2.tgz#08a7f2a8bf734604779a9efa4ad5cc717abb954b"
   dependencies:
     are-we-there-yet "~1.1.2"
     console-control-strings "~1.1.0"
@@ -4490,15 +4480,15 @@ read-pkg@^2.0.0:
     path-type "^2.0.0"
 
 readable-stream@^2.0.0, readable-stream@^2.0.1, readable-stream@^2.0.2, readable-stream@^2.0.5, readable-stream@^2.0.6, readable-stream@^2.1.4, readable-stream@^2.2.2, readable-stream@^2.2.6:
-  version "2.3.2"
-  resolved "https://registry.yarnpkg.com/readable-stream/-/readable-stream-2.3.2.tgz#5a04df05e4f57fe3f0dc68fdd11dc5c97c7e6f4d"
+  version "2.3.3"
+  resolved "https://registry.yarnpkg.com/readable-stream/-/readable-stream-2.3.3.tgz#368f2512d79f9d46fdfc71349ae7878bbc1eb95c"
   dependencies:
     core-util-is "~1.0.0"
     inherits "~2.0.3"
     isarray "~1.0.0"
     process-nextick-args "~1.0.6"
-    safe-buffer "~5.1.0"
-    string_decoder "~1.0.0"
+    safe-buffer "~5.1.1"
+    string_decoder "~1.0.3"
     util-deprecate "~1.0.1"
 
 readdirp@^2.0.0:
@@ -4747,12 +4737,12 @@ rx-lite@^3.1.2:
   resolved "https://registry.yarnpkg.com/rx-lite/-/rx-lite-3.1.2.tgz#19ce502ca572665f3b647b10939f97fd1615f102"
 
 rxjs@^5.0.0-beta.11:
-  version "5.4.1"
-  resolved "https://registry.yarnpkg.com/rxjs/-/rxjs-5.4.1.tgz#b62f757f279445d265a18a58fb0a70dc90e91626"
+  version "5.4.2"
+  resolved "https://registry.yarnpkg.com/rxjs/-/rxjs-5.4.2.tgz#2a3236fcbf03df57bae06fd6972fd99e5c08fcf7"
   dependencies:
     symbol-observable "^1.0.1"
 
-safe-buffer@^5.0.1, safe-buffer@^5.1.0, safe-buffer@~5.1.0:
+safe-buffer@^5.0.1, safe-buffer@^5.1.0, safe-buffer@~5.1.0, safe-buffer@~5.1.1:
   version "5.1.1"
   resolved "https://registry.yarnpkg.com/safe-buffer/-/safe-buffer-5.1.1.tgz#893312af69b2123def71f57889001671eeb2c853"
 
@@ -5054,7 +5044,7 @@ string_decoder@^0.10.25:
   version "0.10.31"
   resolved "https://registry.yarnpkg.com/string_decoder/-/string_decoder-0.10.31.tgz#62e203bc41766c6c28c9fc84301dab1c5310fa94"
 
-string_decoder@~1.0.0:
+string_decoder@~1.0.3:
   version "1.0.3"
   resolved "https://registry.yarnpkg.com/string_decoder/-/string_decoder-1.0.3.tgz#0fc67d7c141825de94282dd536bec6b9bce860ab"
   dependencies:
@@ -5563,11 +5553,11 @@ wordwrap@~1.0.0:
   resolved "https://registry.yarnpkg.com/wordwrap/-/wordwrap-1.0.0.tgz#27584810891456a4171c8d0226441ade90cbcaeb"
 
 worker-farm@^1.3.1:
-  version "1.3.1"
-  resolved "https://registry.yarnpkg.com/worker-farm/-/worker-farm-1.3.1.tgz#4333112bb49b17aa050b87895ca6b2cacf40e5ff"
+  version "1.4.1"
+  resolved "https://registry.yarnpkg.com/worker-farm/-/worker-farm-1.4.1.tgz#a438bc993a7a7d133bcb6547c95eca7cff4897d8"
   dependencies:
-    errno ">=0.1.1 <0.2.0-0"
-    xtend ">=4.0.0 <4.1.0-0"
+    errno "^0.1.4"
+    xtend "^4.0.1"
 
 wrap-ansi@^2.0.0:
   version "2.1.0"
@@ -5613,7 +5603,7 @@ xss-filters@1.2.7:
   version "1.2.7"
   resolved "https://registry.yarnpkg.com/xss-filters/-/xss-filters-1.2.7.tgz#59fa1de201f36f2f3470dcac5f58ccc2830b0a9a"
 
-"xtend@>=4.0.0 <4.1.0-0", xtend@^4.0.0, xtend@^4.0.1:
+xtend@^4.0.0, xtend@^4.0.1:
   version "4.0.1"
   resolved "https://registry.yarnpkg.com/xtend/-/xtend-4.0.1.tgz#a5c6d532be656e23db820efb943a1f04998d63af"