Add generic type for mitt

Co-Authored-By: Tim Suchanek <timsuchanek@users.noreply.github.com>
vercel · Jul 29, 2020 · 0476b70 · 0476b70
1 parent c93b9b1
commit 0476b70
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Showing 4 changed files with 24 additions and 33 deletions.
diff --git a/packages/next/client/router.ts b/packages/next/client/router.ts
@@ -1,6 +1,9 @@
 /* global window */
 import React from 'react'
-import Router, { NextRouter } from '../next-server/lib/router/router'
+import Router, {
+  NextRouter,
+  RouterEvent,
+} from '../next-server/lib/router/router'
 import { RouterContext } from '../next-server/lib/router-context'
 
 type ClassArguments<T> = T extends new (...args: infer U) => any ? U : any
@@ -13,14 +16,6 @@ type SingletonRouterBase = {
   ready(cb: () => any): void
 }
 
-type RouterEvent =
-  | 'routeChangeStart'
-  | 'beforeHistoryChange'
-  | 'routeChangeComplete'
-  | 'routeChangeError'
-  | 'hashChangeStart'
-  | 'hashChangeComplete'
-
 export { Router, NextRouter }
 
 export type SingletonRouter = SingletonRouterBase & NextRouter

diff --git a/packages/next/next-server/lib/mitt.ts b/packages/next/next-server/lib/mitt.ts
@@ -15,29 +15,19 @@ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLI
 // See the LICENSE at the top of the file
 
 type Handler = (...evts: any[]) => void
-
-export type MittEmitter = {
-  on(type: string, handler: Handler): void
-  off(type: string, handler: Handler): void
-  emit(type: string, ...evts: any[]): void
-}
-
-export default function mitt(): MittEmitter {
-  const all: { [s: string]: Handler[] } = Object.create(null)
-
+export default function mitt<T extends string>() {
+  const all: Record<T, Handler[]> = Object.create(null)
   return {
-    on(type: string, handler: Handler) {
+    on(type: T, handler: Handler) {
       ;(all[type] || (all[type] = [])).push(handler)
     },
-
-    off(type: string, handler: Handler) {
+    off(type: T, handler: Handler) {
       if (all[type]) {
         // tslint:disable-next-line:no-bitwise
         all[type].splice(all[type].indexOf(handler) >>> 0, 1)
       }
     },
-
-    emit(type: string, ...evts: any[]) {
+    emit(type: T, ...evts: any[]) {
       // eslint-disable-next-line array-callback-return
       ;(all[type] || []).slice().map((handler: Handler) => {
         handler(...evts)

diff --git a/packages/next/next-server/lib/router/router.ts b/packages/next/next-server/lib/router/router.ts
@@ -3,7 +3,7 @@
 import { ParsedUrlQuery } from 'querystring'
 import { ComponentType } from 'react'
 import { UrlObject } from 'url'
-import mitt, { MittEmitter } from '../mitt'
+import mitt from '../mitt'
 import {
   AppContextType,
   formatWithValidation,
@@ -108,6 +108,14 @@ export type NextRouter = BaseRouter &
     | 'isFallback'
   >
 
+export type RouterEvent =
+  | 'routeChangeStart'
+  | 'beforeHistoryChange'
+  | 'routeChangeComplete'
+  | 'routeChangeError'
+  | 'hashChangeStart'
+  | 'hashChangeComplete'
+
 export type PrefetchOptions = {
   priority?: boolean
 }
@@ -189,13 +197,15 @@ export default class Router implements BaseRouter {
   clc: ComponentLoadCancel
   pageLoader: any
   _bps: BeforePopStateCallback | undefined
-  events: MittEmitter
+  // Backwards compat for Router.router.events
+  // TODO: Should be remove the following major version as it was never documented
+  events = Router.events
   _wrapApp: (App: ComponentType) => any
   isSsr: boolean
   isFallback: boolean
   _inFlightRoute?: string
 
-  static events: MittEmitter = mitt()
+  static events = mitt<RouterEvent>()
 
   constructor(
     pathname: string,
@@ -241,10 +251,6 @@ export default class Router implements BaseRouter {
 
     this.components['/_app'] = { Component: App }
 
-    // Backwards compat for Router.router.events
-    // TODO: Should be remove the following major version as it was never documented
-    this.events = Router.events
-
     this.pageLoader = pageLoader
     this.pathname = pathname
     this.query = query

diff --git a/packages/next/next-server/server/render.tsx b/packages/next/next-server/server/render.tsx
@@ -26,7 +26,7 @@ import { defaultHead } from '../lib/head'
 import { HeadManagerContext } from '../lib/head-manager-context'
 import Loadable from '../lib/loadable'
 import { LoadableContext } from '../lib/loadable-context'
-import mitt, { MittEmitter } from '../lib/mitt'
+import mitt from '../lib/mitt'
 import { RouterContext } from '../lib/router-context'
 import { NextRouter } from '../lib/router/router'
 import { isDynamicRoute } from '../lib/router/utils/is-dynamic'
@@ -61,7 +61,7 @@ class ServerRouter implements NextRouter {
   events: any
   isFallback: boolean
   // TODO: Remove in the next major version, as this would mean the user is adding event listeners in server-side `render` method
-  static events: MittEmitter = mitt()
+  static events = mitt<string>()
 
   constructor(
     pathname: string,