From e75e1911afdf81c08184c5dd8e115a3b738f8c0a Mon Sep 17 00:00:00 2001
From: Daniel Roe <daniel@concision.co.uk>
Date: Fri, 31 Jul 2020 10:37:31 +0100
Subject: [PATCH] types: increase types coverage (#13)

---
 packages/nuxt3/src/builder/builder.ts         | 35 +++++++++--
 packages/nuxt3/src/builder/context/build.ts   |  9 ++-
 .../nuxt3/src/builder/context/template.ts     | 12 ++--
 packages/nuxt3/src/builder/ignore.ts          | 11 +++-
 packages/nuxt3/src/builder/index.ts           |  6 +-
 packages/nuxt3/src/cli/command.ts             | 63 ++++++++++++++-----
 packages/nuxt3/src/cli/commands/build.ts      | 13 ++--
 packages/nuxt3/src/cli/commands/dev.ts        | 17 +++--
 packages/nuxt3/src/cli/commands/export.ts     |  3 +-
 packages/nuxt3/src/cli/commands/generate.ts   | 10 +--
 packages/nuxt3/src/cli/commands/help.ts       |  2 +-
 packages/nuxt3/src/cli/commands/index.ts      |  2 +-
 packages/nuxt3/src/cli/commands/serve.ts      |  7 ++-
 packages/nuxt3/src/cli/commands/start.ts      |  4 +-
 packages/nuxt3/src/cli/commands/webpack.ts    |  4 +-
 packages/nuxt3/src/cli/list.ts                |  2 +-
 packages/nuxt3/src/cli/run.ts                 |  6 +-
 packages/nuxt3/src/cli/setup.ts               |  2 +-
 packages/nuxt3/src/cli/utils/banner.ts        |  6 +-
 packages/nuxt3/src/cli/utils/config.ts        |  4 +-
 packages/nuxt3/src/cli/utils/formatting.ts    | 18 +++---
 packages/nuxt3/src/cli/utils/index.ts         |  8 +--
 packages/nuxt3/src/cli/utils/webpack.ts       |  2 +-
 packages/nuxt3/src/config/load.ts             | 24 ++++---
 packages/nuxt3/src/core/load.ts               | 15 ++++-
 packages/nuxt3/src/core/module.ts             | 28 +++++++--
 packages/nuxt3/src/core/nuxt.ts               | 18 +++++-
 packages/nuxt3/src/core/resolver.ts           | 56 ++++++++---------
 packages/nuxt3/src/generator/generator.ts     | 24 ++++++-
 packages/nuxt3/src/generator/index.ts         |  4 +-
 packages/nuxt3/src/server/context.ts          |  9 ++-
 packages/nuxt3/src/server/jsdom.ts            | 14 +++--
 packages/nuxt3/src/server/listener.ts         | 19 +++++-
 .../nuxt3/src/server/middleware/timing.ts     | 17 +++--
 packages/nuxt3/src/server/server.ts           | 50 ++++++++++++---
 packages/nuxt3/src/utils/cjs.ts               | 12 ++--
 packages/nuxt3/src/utils/constants.ts         |  8 ++-
 packages/nuxt3/src/utils/context.ts           | 30 ++++++---
 packages/nuxt3/src/utils/lang.ts              | 29 +++++----
 packages/nuxt3/src/utils/locking.ts           | 39 +++++++++---
 packages/nuxt3/src/utils/modern.ts            | 47 +++++++++-----
 packages/nuxt3/src/utils/resolve.ts           | 37 +++++++----
 packages/nuxt3/src/utils/route.ts             | 51 ++++++++++-----
 packages/nuxt3/src/utils/serialize.ts         | 10 ++-
 packages/nuxt3/src/utils/task.ts              | 12 +++-
 packages/nuxt3/src/utils/timer.ts             | 57 ++++++++++++-----
 packages/nuxt3/src/vue-renderer/renderer.ts   | 31 ++++++---
 .../nuxt3/src/vue-renderer/renderers/base.ts  | 11 +++-
 .../src/vue-renderer/renderers/modern.ts      |  9 ++-
 .../nuxt3/src/vue-renderer/renderers/spa.ts   | 15 ++++-
 .../nuxt3/src/vue-renderer/renderers/ssr.ts   |  6 +-
 51 files changed, 667 insertions(+), 261 deletions(-)

diff --git a/packages/nuxt3/src/builder/builder.ts b/packages/nuxt3/src/builder/builder.ts
index 7c6c1697e7..52f6c1e861 100644
--- a/packages/nuxt3/src/builder/builder.ts
+++ b/packages/nuxt3/src/builder/builder.ts
@@ -8,6 +8,7 @@ import hash from 'hash-sum'
 import pify from 'pify'
 import upath from 'upath'
 import semver from 'semver'
+import type { RouteLocationRaw } from 'vue-router'
 
 import debounce from 'lodash/debounce'
 import omit from 'lodash/omit'
@@ -15,6 +16,7 @@ import template from 'lodash/template'
 import uniq from 'lodash/uniq'
 import uniqBy from 'lodash/uniqBy'
 
+import type { Nuxt } from 'nuxt/core'
 import { BundleBuilder } from 'nuxt/webpack'
 import vueAppTemplate from 'nuxt/vue-app/template'
 
@@ -26,6 +28,7 @@ import {
   determineGlobals,
   stripWhitespace,
   isIndexFileAndFolder,
+  DeterminedGlobals,
   scanRequireTree,
   TARGETS,
   isFullStatic
@@ -37,7 +40,31 @@ import TemplateContext from './context/template'
 
 const glob = pify(Glob)
 export default class Builder {
-  constructor (nuxt, bundleBuilder) {
+  __closed?: boolean
+  _buildStatus: typeof STATUS[keyof typeof STATUS]
+  _defaultPage?: boolean
+  _nuxtPages?: boolean
+
+  appFiles: string[]
+  bundleBuilder: BundleBuilder
+  globals: DeterminedGlobals
+  ignore: Ignore
+  nuxt: Nuxt
+  options: Nuxt['options']
+  plugins: Array<{
+    src: string
+  }>
+  relativeToBuild: (...args: string[]) => string
+  routes: RouteLocationRaw[]
+  supportedExtensions: string[]
+  template: typeof vueAppTemplate
+  watchers: {
+    files: null
+    custom: null
+    restart: null
+  }
+
+  constructor (nuxt: Nuxt) {
     this.nuxt = nuxt
     this.plugins = []
     this.options = nuxt.options
@@ -51,7 +78,7 @@ export default class Builder {
     this.supportedExtensions = ['vue', 'js', ...(this.options.build.additionalExtensions || [])]
 
     // Helper to resolve build paths
-    this.relativeToBuild = (...args) => relativeTo(this.options.buildDir, ...args)
+    this.relativeToBuild = (...args: string[]) => relativeTo(this.options.buildDir, ...args)
 
     this._buildStatus = STATUS.INITIAL
 
@@ -81,7 +108,7 @@ export default class Builder {
     this.template = vueAppTemplate
 
     // Create a new bundle builder
-    this.bundleBuilder = this.getBundleBuilder(bundleBuilder)
+    this.bundleBuilder = this.getBundleBuilder()
 
     this.ignore = new Ignore({
       rootDir: this.options.srcDir,
@@ -846,4 +873,4 @@ const STATUS = {
   INITIAL: 1,
   BUILD_DONE: 2,
   BUILDING: 3
-}
+} as const
diff --git a/packages/nuxt3/src/builder/context/build.ts b/packages/nuxt3/src/builder/context/build.ts
index 9f0931e7f8..28efbfac28 100644
--- a/packages/nuxt3/src/builder/context/build.ts
+++ b/packages/nuxt3/src/builder/context/build.ts
@@ -1,5 +1,12 @@
+import type Builder from '../builder'
+
 export default class BuildContext {
-  constructor (builder) {
+  _builder: Builder
+  nuxt: Builder['nuxt']
+  options: Builder['nuxt']['options']
+  target: Builder['nuxt']['options']['target']
+  
+  constructor (builder: Builder) {
     this._builder = builder
     this.nuxt = builder.nuxt
     this.options = builder.nuxt.options
diff --git a/packages/nuxt3/src/builder/context/template.ts b/packages/nuxt3/src/builder/context/template.ts
index 7b11dd5b4c..952ecb001f 100644
--- a/packages/nuxt3/src/builder/context/template.ts
+++ b/packages/nuxt3/src/builder/context/template.ts
@@ -1,19 +1,23 @@
 import hash from 'hash-sum'
-import consola from 'consola'
 import uniqBy from 'lodash/uniqBy'
 import serialize from 'serialize-javascript'
 
 import devalue from '@nuxt/devalue'
 import { r, wp, wChunk, serializeFunction, isFullStatic } from 'nuxt/utils'
 
+import type Builder from '../builder'
+
 export default class TemplateContext {
-  constructor(builder, options) {
+  templateFiles: string[]
+  templateVars: any
+
+  constructor (builder: Builder, options) {
     this.templateFiles = Array.from(builder.template.files)
     this.templateVars = {
       nuxtOptions: options,
       features: options.features,
       extensions: options.extensions
-        .map(ext => ext.replace(/^\./, ''))
+        .map((ext: string) => ext.replace(/^\./, ''))
         .join('|'),
       messages: options.messages,
       splitChunks: options.build.splitChunks,
@@ -62,7 +66,7 @@ export default class TemplateContext {
         hash,
         r,
         wp,
-        wChunk,
+        wChunk
       },
       interpolate: /<%=([\s\S]+?)%>/g
     }
diff --git a/packages/nuxt3/src/builder/ignore.ts b/packages/nuxt3/src/builder/ignore.ts
index d929368960..4eb58048dd 100644
--- a/packages/nuxt3/src/builder/ignore.ts
+++ b/packages/nuxt3/src/builder/ignore.ts
@@ -2,7 +2,16 @@ import path from 'path'
 import fs from 'fs-extra'
 import ignore from 'ignore'
 
+type IgnoreInstance = ReturnType<typeof ignore>
+type IgnoreOptions = Parameters<typeof ignore>[0]
+
 export default class Ignore {
+  rootDir: string
+  ignore?: IgnoreInstance
+  ignoreArray?: string | string
+  ignoreFile?: string
+  ignoreOptions?: IgnoreOptions
+
   constructor (options) {
     this.rootDir = options.rootDir
     this.ignoreOptions = options.ignoreOptions
@@ -44,7 +53,7 @@ export default class Ignore {
     }
   }
 
-  filter (paths) {
+  filter (paths: string[]) {
     if (this.ignore) {
       return this.ignore.filter([].concat(paths || []))
     }
diff --git a/packages/nuxt3/src/builder/index.ts b/packages/nuxt3/src/builder/index.ts
index e00c399dec..2fcfa1b131 100644
--- a/packages/nuxt3/src/builder/index.ts
+++ b/packages/nuxt3/src/builder/index.ts
@@ -1,10 +1,12 @@
+import type { Nuxt } from 'nuxt/core'
+
 import Builder from './builder'
 export { default as Builder } from './builder'
 
-export function getBuilder (nuxt) {
+export function getBuilder (nuxt: Nuxt) {
   return new Builder(nuxt)
 }
 
-export function build (nuxt) {
+export function build (nuxt: Nuxt) {
   return getBuilder(nuxt).build()
 }
diff --git a/packages/nuxt3/src/cli/command.ts b/packages/nuxt3/src/cli/command.ts
index 6b8824085e..4c7ef4efc8 100644
--- a/packages/nuxt3/src/cli/command.ts
+++ b/packages/nuxt3/src/cli/command.ts
@@ -1,36 +1,67 @@
 
 import path from 'path'
 import consola from 'consola'
-import minimist from 'minimist'
-import Hookable from 'hable'
+import minimist, { ParsedArgs } from 'minimist'
+import Hookable from 'hookable'
+
+import { Nuxt } from 'nuxt/core'
+import { Builder } from 'nuxt/builder'
+import { Generator } from 'nuxt/generator'
+import type { Target } from 'nuxt/utils'
+
 import { name, version } from '../../package.json'
+
 import { forceExit } from './utils'
 import { loadNuxtConfig } from './utils/config'
 import { indent, foldLines, colorize } from './utils/formatting'
 import { startSpaces, optionSpaces, forceExitTimeout } from './utils/constants'
-import { Nuxt } from 'nuxt/core'
-import { Builder } from 'nuxt/builder'
-import { Generator } from 'nuxt/generator'
+
+export interface Command {
+  name: string
+  usage: string
+  description: string
+  options?: Record<string, any>
+  run?: (nuxt: NuxtCommand) => any | Promise<any>
+}
+
+type Hooks = Parameters<Hookable['addHooks']>[0]
+
+interface ExtraOptions {
+  _build?: boolean
+  _cli?: boolean
+  _export?: boolean
+  _generate?: boolean
+  _start?: boolean
+  dev?: boolean
+  server?: boolean
+  target?: Target
+}
 
 export default class NuxtCommand extends Hookable {
-  constructor (cmd = { name: '', usage: '', description: '' }, argv = process.argv.slice(2), hooks = {}) {
+  _argv: string[]
+  _parsedArgv: null | ParsedArgs
+  _lockRelease?: () => Promise<any>
+
+  cmd: Command & { options: Command['options'] }
+
+  constructor (cmd: Command = { name: '', usage: '', description: '' }, argv = process.argv.slice(2), hooks: Hooks = {}) {
     super(consola)
     this.addHooks(hooks)
 
     if (!cmd.options) {
       cmd.options = {}
     }
-    this.cmd = cmd
+    this.cmd = cmd as Command & { options: Command['options'] }
 
     this._argv = Array.from(argv)
     this._parsedArgv = null // Lazy evaluate
   }
 
-  static run (cmd, argv, hooks) {
+  static run (cmd: Command, argv: NodeJS.Process['argv'], hooks: Hooks) {
     return NuxtCommand.from(cmd, argv, hooks).run()
   }
 
-  static from (cmd, argv, hooks) {
+  static from (cmd: Command, argv: NodeJS.Process['argv'], hooks: Hooks) {
     if (cmd instanceof NuxtCommand) {
       return cmd
     }
@@ -54,11 +85,11 @@ export default class NuxtCommand extends Hookable {
       return
     }
 
-    if (typeof this.cmd.run !== 'function') {
+    if (!(this.cmd.run instanceof Function)) {
       throw new TypeError('Invalid command! Commands should at least implement run() function.')
     }
 
-    let cmdError
+    let cmdError: any
 
     try {
       await this.cmd.run(this)
@@ -102,7 +133,7 @@ export default class NuxtCommand extends Hookable {
     return this._parsedArgv
   }
 
-  async getNuxtConfig (extraOptions = {}) {
+  async getNuxtConfig (extraOptions: ExtraOptions = {}) {
     // Flag to indicate nuxt is running with CLI (not programmatic)
     extraOptions._cli = true
 
@@ -131,7 +162,7 @@ export default class NuxtCommand extends Hookable {
     return nuxt
   }
 
-  async getBuilder (nuxt) {
+  async getBuilder (nuxt: Nuxt) {
     return new Builder(nuxt)
   }
 
@@ -160,12 +191,12 @@ export default class NuxtCommand extends Hookable {
     }
   }
 
-  isUserSuppliedArg (option) {
+  isUserSuppliedArg (option: string) {
     return this._argv.includes(`--${option}`) || this._argv.includes(`--no-${option}`)
   }
 
-  _getDefaultOptionValue (option) {
-    return typeof option.default === 'function' ? option.default(this.cmd) : option.default
+  _getDefaultOptionValue<T, Option extends { default: ((cmd: Command) => T) | T }>(option: Option) {
+    return option.default instanceof Function ? option.default(this.cmd) : option.default
   }
 
   _getMinimistOptions () {
diff --git a/packages/nuxt3/src/cli/commands/build.ts b/packages/nuxt3/src/cli/commands/build.ts
index f234b3661b..ff4a771513 100644
--- a/packages/nuxt3/src/cli/commands/build.ts
+++ b/packages/nuxt3/src/cli/commands/build.ts
@@ -1,5 +1,8 @@
 import consola from 'consola'
+import type { ParsedArgs } from 'minimist'
+
 import { MODES, TARGETS } from 'nuxt/utils'
+import NuxtCommand from '../command'
 import { common, locking } from '../options'
 import { createLock } from '../utils'
 
@@ -14,7 +17,7 @@ export default {
       alias: 'a',
       type: 'boolean',
       description: 'Launch webpack-bundle-analyzer to optimize your bundles',
-      prepare (cmd, options, argv) {
+      prepare (_cmd: NuxtCommand, options, argv: ParsedArgs) {
         // Analyze option
         options.build = options.build || {}
         if (argv.analyze && typeof options.build.analyze !== 'object') {
@@ -26,7 +29,7 @@ export default {
       type: 'boolean',
       default: false,
       description: 'Enable Vue devtools',
-      prepare (cmd, options, argv) {
+      prepare (_cmd: NuxtCommand, options, argv: ParsedArgs) {
         options.vue = options.vue || {}
         options.vue.config = options.vue.config || {}
         if (argv.devtools) {
@@ -43,7 +46,7 @@ export default {
       alias: 'q',
       type: 'boolean',
       description: 'Disable output except for errors',
-      prepare (cmd, options, argv) {
+      prepare (_cmd: NuxtCommand, options, argv: ParsedArgs) {
         // Silence output when using --quiet
         options.build = options.build || {}
         if (argv.quiet) {
@@ -55,14 +58,14 @@ export default {
       type: 'boolean',
       default: false,
       description: 'Bundle all server dependencies (useful for nuxt-start)',
-      prepare (cmd, options, argv) {
+      prepare (_cmd: NuxtCommand, options, argv: ParsedArgs) {
         if (argv.standalone) {
           options.build.standalone = true
         }
       }
     }
   },
-  async run (cmd) {
+  async run (cmd: NuxtCommand) {
     const config = await cmd.getNuxtConfig({ dev: false, server: false, _build: true })
     config.server = (config.mode === MODES.spa || config.ssr === false) && cmd.argv.generate !== false
     const nuxt = await cmd.getNuxt(config)
diff --git a/packages/nuxt3/src/cli/commands/dev.ts b/packages/nuxt3/src/cli/commands/dev.ts
index 9674bca052..bfb05c8a3f 100644
--- a/packages/nuxt3/src/cli/commands/dev.ts
+++ b/packages/nuxt3/src/cli/commands/dev.ts
@@ -1,6 +1,11 @@
 import consola from 'consola'
 import chalk from 'chalk'
 import opener from 'opener'
+import type { ParsedArgs } from 'minimist'
+
+import { Nuxt } from 'nuxt/core'
+
+import type NuxtCommand from '../command'
 import { common, server } from '../options'
 import { eventsMapping, formatPath } from '../utils'
 import { showBanner } from '../utils/banner'
@@ -20,13 +25,13 @@ export default {
     }
   },
 
-  async run (cmd) {
+  async run (cmd: NuxtCommand) {
     const { argv } = cmd
 
     await this.startDev(cmd, argv, argv.open)
   },
 
-  async startDev (cmd, argv) {
+  async startDev (cmd: NuxtCommand, argv) {
     let nuxt
     try {
       nuxt = await this._listenDev(cmd, argv)
@@ -45,7 +50,7 @@ export default {
     return nuxt
   },
 
-  async _listenDev (cmd, argv) {
+  async _listenDev (cmd: NuxtCommand, argv: ParsedArgs) {
     const config = await cmd.getNuxtConfig({ dev: true, _build: true })
     const nuxt = await cmd.getNuxt(config)
 
@@ -73,7 +78,7 @@ export default {
     return nuxt
   },
 
-  async _buildDev (cmd, argv, nuxt) {
+  async _buildDev (cmd: NuxtCommand, _argv: ParsedArgs, nuxt: Nuxt) {
     // Create builder instance
     const builder = await cmd.getBuilder(nuxt)
 
@@ -92,7 +97,7 @@ export default {
     return nuxt
   },
 
-  logChanged ({ event, path }) {
+  logChanged ({ event, path }: { event: keyof typeof eventsMapping, path: string }) {
     const { icon, color, action } = eventsMapping[event] || eventsMapping.change
 
     consola.log({
@@ -110,7 +115,7 @@ export default {
     await this.startDev(cmd, argv)
   },
 
-  onBundlerChange (path) {
+  onBundlerChange (path: string) {
     this.logChanged({ event: 'change', path })
   }
 }
diff --git a/packages/nuxt3/src/cli/commands/export.ts b/packages/nuxt3/src/cli/commands/export.ts
index 026200c3fe..825d8bd941 100644
--- a/packages/nuxt3/src/cli/commands/export.ts
+++ b/packages/nuxt3/src/cli/commands/export.ts
@@ -1,6 +1,7 @@
 import path from 'path'
 import consola from 'consola'
 import { TARGETS } from 'nuxt/utils'
+import type NuxtCommand from '../command'
 import { common, locking } from '../options'
 import { createLock } from '../utils'
 
@@ -17,7 +18,7 @@ export default {
       description: 'Exit with non-zero status code if there are errors when exporting pages'
     }
   },
-  async run (cmd) {
+  async run (cmd: NuxtCommand) {
     const config = await cmd.getNuxtConfig({
       dev: false,
       target: TARGETS.static,
diff --git a/packages/nuxt3/src/cli/commands/generate.ts b/packages/nuxt3/src/cli/commands/generate.ts
index b7386626a8..d7c2e6f1cc 100644
--- a/packages/nuxt3/src/cli/commands/generate.ts
+++ b/packages/nuxt3/src/cli/commands/generate.ts
@@ -1,4 +1,6 @@
+import type { ParsedArgs } from 'minimist'
 import { TARGETS } from 'nuxt/utils'
+import type NuxtCommand from '../command'
 import { common, locking } from '../options'
 import { normalizeArg, createLock } from '../utils'
 
@@ -18,7 +20,7 @@ export default {
       type: 'boolean',
       default: false,
       description: 'Enable Vue devtools',
-      prepare (cmd, options, argv) {
+      prepare (_cmd: NuxtCommand, options, argv: ParsedArgs) {
         options.vue = options.vue || {}
         options.vue.config = options.vue.config || {}
         if (argv.devtools) {
@@ -30,7 +32,7 @@ export default {
       alias: 'q',
       type: 'boolean',
       description: 'Disable output except for errors',
-      prepare (cmd, options, argv) {
+      prepare (_cmd: NuxtCommand, options, argv: ParsedArgs) {
         // Silence output when using --quiet
         options.build = options.build || {}
         if (argv.quiet) {
@@ -41,7 +43,7 @@ export default {
     modern: {
       ...common.modern,
       description: 'Generate app in modern build (modern mode can be only client)',
-      prepare (cmd, options, argv) {
+      prepare (_cmd: NuxtCommand, options, argv: ParsedArgs) {
         if (normalizeArg(argv.modern)) {
           options.modern = 'client'
         }
@@ -53,7 +55,7 @@ export default {
       description: 'Exit with non-zero status code if there are errors when generating pages'
     }
   },
-  async run (cmd) {
+  async run (cmd: NuxtCommand) {
     const config = await cmd.getNuxtConfig({
       dev: false,
       _build: cmd.argv.build,
diff --git a/packages/nuxt3/src/cli/commands/help.ts b/packages/nuxt3/src/cli/commands/help.ts
index 4b702cd1df..dc7b34bd9a 100644
--- a/packages/nuxt3/src/cli/commands/help.ts
+++ b/packages/nuxt3/src/cli/commands/help.ts
@@ -12,7 +12,7 @@ export default {
     help: common.help,
     version: common.version
   },
-  async run (cmd) {
+  async run (cmd: NuxtCommand) {
     const [name] = cmd._argv
     if (!name) {
       return listCommands()
diff --git a/packages/nuxt3/src/cli/commands/index.ts b/packages/nuxt3/src/cli/commands/index.ts
index 50e84854d4..52f282992b 100644
--- a/packages/nuxt3/src/cli/commands/index.ts
+++ b/packages/nuxt3/src/cli/commands/index.ts
@@ -9,7 +9,7 @@ const _commands = {
   help: () => import('./help')
 }
 
-export default function getCommand (name) {
+export default function getCommand (name: keyof typeof _commands) {
   if (!_commands[name]) {
     return Promise.resolve(null)
   }
diff --git a/packages/nuxt3/src/cli/commands/serve.ts b/packages/nuxt3/src/cli/commands/serve.ts
index 071c65f3b5..ee79274483 100644
--- a/packages/nuxt3/src/cli/commands/serve.ts
+++ b/packages/nuxt3/src/cli/commands/serve.ts
@@ -5,10 +5,11 @@ import serveStatic from 'serve-static'
 import compression from 'compression'
 import { getNuxtConfig } from 'nuxt/config'
 import { TARGETS } from 'nuxt/utils'
-import { common, server } from '../options'
-import { showBanner } from '../utils/banner'
 import { Listener } from 'nuxt/server'
 import { Nuxt } from 'nuxt/core'
+import type NuxtCommand from '../command'
+import { common, server } from '../options'
+import { showBanner } from '../utils/banner'
 
 export default {
   name: 'serve',
@@ -20,7 +21,7 @@ export default {
     help: common.help,
     ...server
   },
-  async run (cmd) {
+  async run (cmd: NuxtCommand) {
     let options = await cmd.getNuxtConfig({ dev: false })
     // add default options
     options = getNuxtConfig(options)
diff --git a/packages/nuxt3/src/cli/commands/start.ts b/packages/nuxt3/src/cli/commands/start.ts
index 3da1c2c711..97746d020e 100644
--- a/packages/nuxt3/src/cli/commands/start.ts
+++ b/packages/nuxt3/src/cli/commands/start.ts
@@ -1,4 +1,6 @@
 import { TARGETS } from 'nuxt/utils'
+
+import type NuxtCommand from '../command'
 import { common, server } from '../options'
 import { showBanner } from '../utils/banner'
 
@@ -10,7 +12,7 @@ export default {
     ...common,
     ...server
   },
-  async run (cmd) {
+  async run (cmd: NuxtCommand) {
     const config = await cmd.getNuxtConfig({ dev: false, _start: true })
     if (config.target === TARGETS.static) {
       throw new Error('You cannot use `nuxt start` with ' + TARGETS.static + ' target, please use `nuxt export` and `nuxt serve`')
diff --git a/packages/nuxt3/src/cli/commands/webpack.ts b/packages/nuxt3/src/cli/commands/webpack.ts
index 5d453f3308..9c881cf94d 100644
--- a/packages/nuxt3/src/cli/commands/webpack.ts
+++ b/packages/nuxt3/src/cli/commands/webpack.ts
@@ -1,6 +1,8 @@
 import util from 'util'
 import consola from 'consola'
 import get from 'lodash/get'
+
+import type NuxtCommand from '../command'
 import { common } from '../options'
 
 export default {
@@ -32,7 +34,7 @@ export default {
       description: 'Inspect development mode webpack config'
     }
   },
-  async run (cmd) {
+  async run (cmd: NuxtCommand) {
     const { name } = cmd.argv
     const queries = [...cmd.argv._]
 
diff --git a/packages/nuxt3/src/cli/list.ts b/packages/nuxt3/src/cli/list.ts
index 13d21d997a..ca31a82df4 100644
--- a/packages/nuxt3/src/cli/list.ts
+++ b/packages/nuxt3/src/cli/list.ts
@@ -4,7 +4,7 @@ import { startSpaces, optionSpaces } from './utils/constants'
 import getCommand from './commands'
 
 export default async function listCommands () {
-  const commandsOrder = ['dev', 'build', 'generate', 'start', 'help']
+  const commandsOrder = ['dev', 'build', 'generate', 'start', 'help'] as const
 
   // Load all commands
   const _commands = await Promise.all(
diff --git a/packages/nuxt3/src/cli/run.ts b/packages/nuxt3/src/cli/run.ts
index 859c0479a7..3d64fdd94e 100644
--- a/packages/nuxt3/src/cli/run.ts
+++ b/packages/nuxt3/src/cli/run.ts
@@ -5,7 +5,7 @@ import NuxtCommand from './command'
 import setup from './setup'
 import getCommand from './commands'
 
-function packageExists (name) {
+function packageExists (name: string) {
   try {
     require.resolve(name)
     return true
@@ -14,7 +14,7 @@ function packageExists (name) {
   }
 }
 
-export default async function run(_argv, hooks = {}) {
+export default async function run (_argv: NodeJS.Process['argv'], hooks = {}) {
   // Check for not installing both nuxt and nuxt-edge
   const dupPkg = '@nuxt/' + (pkgName === '@nuxt/cli-edge' ? 'cli' : 'cli-edge')
   if (packageExists(dupPkg)) {
@@ -25,7 +25,7 @@ export default async function run(_argv, hooks = {}) {
   const argv = _argv ? Array.from(_argv) : process.argv.slice(2)
 
   // Check for internal command
-  let cmd = await getCommand(argv[0])
+  let cmd = await getCommand(argv[0] as any)
 
   // Matching `nuxt` or `nuxt [dir]` or `nuxt -*` for `nuxt dev` shortcut
   if (!cmd && (!argv[0] || argv[0][0] === '-' || (argv[0] !== 'static' && fs.existsSync(argv[0])))) {
diff --git a/packages/nuxt3/src/cli/setup.ts b/packages/nuxt3/src/cli/setup.ts
index 1fba67e2ca..e42ab55a61 100644
--- a/packages/nuxt3/src/cli/setup.ts
+++ b/packages/nuxt3/src/cli/setup.ts
@@ -4,7 +4,7 @@ import { fatalBox } from './utils/formatting'
 
 let _setup = false
 
-export default function setup ({ dev }) {
+export default function setup ({ dev }: { dev: boolean }) {
   // Apply default NODE_ENV if not provided
   if (!process.env.NODE_ENV) {
     process.env.NODE_ENV = dev ? 'development' : 'production'
diff --git a/packages/nuxt3/src/cli/utils/banner.ts b/packages/nuxt3/src/cli/utils/banner.ts
index 496c5d0faa..fad81f9f08 100644
--- a/packages/nuxt3/src/cli/utils/banner.ts
+++ b/packages/nuxt3/src/cli/utils/banner.ts
@@ -1,10 +1,12 @@
 import consola from 'consola'
 import env from 'std-env'
 import chalk from 'chalk'
+
+import { Nuxt } from 'nuxt/core'
 import { successBox } from './formatting'
 import { getFormattedMemoryUsage } from './memory'
 
-export function showBanner (nuxt, showMemoryUsage = true) {
+export function showBanner (nuxt: Nuxt, showMemoryUsage = true) {
   if (env.test) {
     return
   }
@@ -23,7 +25,7 @@ export function showBanner (nuxt, showMemoryUsage = true) {
   const { bannerColor, badgeMessages } = nuxt.options.cli
   titleLines.push(`${chalk[bannerColor].bold('Nuxt.js')} @ ${nuxt.constructor.version || 'exotic'}\n`)
 
-  const label = name => chalk.bold.cyan(`▸ ${name}:`)
+  const label = (name: string) => chalk.bold.cyan(`▸ ${name}:`)
 
   // Environment
   const isDev = nuxt.options.dev
diff --git a/packages/nuxt3/src/cli/utils/config.ts b/packages/nuxt3/src/cli/utils/config.ts
index 97804f738d..3296afa2fd 100644
--- a/packages/nuxt3/src/cli/utils/config.ts
+++ b/packages/nuxt3/src/cli/utils/config.ts
@@ -1,9 +1,11 @@
 import path from 'path'
 import defaultsDeep from 'lodash/defaultsDeep'
+import type { ParsedArgs } from 'minimist'
+
 import { loadNuxtConfig as _loadNuxtConfig, getDefaultNuxtConfig } from 'nuxt/config'
 import { MODES } from 'nuxt/utils'
 
-export async function loadNuxtConfig (argv, configContext) {
+export async function loadNuxtConfig (argv: ParsedArgs, configContext) {
   const rootDir = path.resolve(argv._[0] || '.')
   const configFile = argv['config-file']
 
diff --git a/packages/nuxt3/src/cli/utils/formatting.ts b/packages/nuxt3/src/cli/utils/formatting.ts
index c085eab83c..d91cdf0c61 100644
--- a/packages/nuxt3/src/cli/utils/formatting.ts
+++ b/packages/nuxt3/src/cli/utils/formatting.ts
@@ -3,11 +3,11 @@ import chalk from 'chalk'
 import boxen from 'boxen'
 import { maxCharsPerLine } from './constants'
 
-export function indent (count, chr = ' ') {
+export function indent (count: number, chr = ' ') {
   return chr.repeat(count)
 }
 
-export function indentLines (string, spaces, firstLineSpaces) {
+export function indentLines (string: string | string[], spaces: number, firstLineSpaces?: number) {
   const lines = Array.isArray(string) ? string : string.split('\n')
   let s = ''
   if (lines.length) {
@@ -21,11 +21,11 @@ export function indentLines (string, spaces, firstLineSpaces) {
   return s
 }
 
-export function foldLines (string, spaces, firstLineSpaces, charsPerLine = maxCharsPerLine()) {
+export function foldLines (string: string, spaces: number, firstLineSpaces?: number, charsPerLine = maxCharsPerLine()) {
   return indentLines(wrapAnsi(string, charsPerLine), spaces, firstLineSpaces)
 }
 
-export function colorize (text) {
+export function colorize (text: string) {
   return text
     .replace(/\[[^ ]+]/g, m => chalk.grey(m))
     .replace(/<[^ ]+>/g, m => chalk.green(m))
@@ -33,7 +33,7 @@ export function colorize (text) {
     .replace(/`([^`]+)`/g, (_, m) => chalk.bold.cyan(m))
 }
 
-export function box (message, title, options) {
+export function box (message: string, title: string, options?: boxen.Options) {
   return boxen([
     title || chalk.white('Nuxt Message'),
     '',
@@ -46,24 +46,24 @@ export function box (message, title, options) {
   }, options)) + '\n'
 }
 
-export function successBox (message, title) {
+export function successBox (message: string, title?: string) {
   return box(message, title || chalk.green('✔ Nuxt Success'), {
     borderColor: 'green'
   })
 }
 
-export function warningBox (message, title) {
+export function warningBox (message: string, title?: string) {
   return box(message, title || chalk.yellow('⚠ Nuxt Warning'), {
     borderColor: 'yellow'
   })
 }
 
-export function errorBox (message, title) {
+export function errorBox (message: string, title?: string) {
   return box(message, title || chalk.red('✖ Nuxt Error'), {
     borderColor: 'red'
   })
 }
 
-export function fatalBox (message, title) {
+export function fatalBox (message: string, title?: string) {
   return errorBox(message, title || chalk.red('✖ Nuxt Fatal Error'))
 }
diff --git a/packages/nuxt3/src/cli/utils/index.ts b/packages/nuxt3/src/cli/utils/index.ts
index 27c6dec9bf..b52c654fb7 100644
--- a/packages/nuxt3/src/cli/utils/index.ts
+++ b/packages/nuxt3/src/cli/utils/index.ts
@@ -12,7 +12,7 @@ export const eventsMapping = {
   unlink: { icon: '-', color: 'red', action: 'Removed' }
 }
 
-export function formatPath (filePath) {
+export function formatPath (filePath: string) {
   if (!filePath) {
     return
   }
@@ -27,7 +27,7 @@ export function formatPath (filePath) {
  * @param {*} defaultValue
  * @returns formatted argument
  */
-export function normalizeArg (arg, defaultValue) {
+export function normalizeArg (arg: boolean | 'true' | '' | 'false', defaultValue?: boolean) {
   switch (arg) {
     case 'true': arg = true; break
     case '': arg = true; break
@@ -37,7 +37,7 @@ export function normalizeArg (arg, defaultValue) {
   return arg
 }
 
-export function forceExit (cmdName, timeout) {
+export function forceExit (cmdName: string, timeout: number | false) {
   if (timeout !== false) {
     const exitTimeout = setTimeout(() => {
       const msg = `The command 'nuxt ${cmdName}' finished but did not exit after ${timeout}s
@@ -59,6 +59,6 @@ ${chalk.bold('DeprecationWarning: Starting with Nuxt version 3 this will be a fa
 
 // An immediate export throws an error when mocking with jest
 // TypeError: Cannot set property createLock of #<Object> which has only a getter
-export function createLock (...args) {
+export function createLock (...args: Parameters<typeof lock>) {
   return lock(...args)
 }
diff --git a/packages/nuxt3/src/cli/utils/webpack.ts b/packages/nuxt3/src/cli/utils/webpack.ts
index 53c3c1a84d..a95d461271 100644
--- a/packages/nuxt3/src/cli/utils/webpack.ts
+++ b/packages/nuxt3/src/cli/utils/webpack.ts
@@ -1,7 +1,7 @@
 import { loadNuxt } from 'nuxt/core'
 import { getBuilder } from 'nuxt/builder'
 
-export async function getWebpackConfig(name = 'client', loadOptions = {}) {
+export async function getWebpackConfig (name = 'client', loadOptions = {}) {
   const nuxt = await loadNuxt(loadOptions)
   const builder = await getBuilder(nuxt)
   const { bundleBuilder } = builder
diff --git a/packages/nuxt3/src/config/load.ts b/packages/nuxt3/src/config/load.ts
index 8e2c4cf1c7..5a256d182b 100644
--- a/packages/nuxt3/src/config/load.ts
+++ b/packages/nuxt3/src/config/load.ts
@@ -8,18 +8,27 @@ import jiti from 'jiti'
 import _createRequire from 'create-require'
 import destr from 'destr'
 import * as rc from 'rc9'
+
+import { LoadOptions } from 'nuxt/core/load'
 import { defaultNuxtConfigFile } from './config'
 
+// @ts-ignore
 const isJest = typeof jest !== 'undefined'
 
+export interface EnvConfig {
+  dotenv?: string
+  env?: NodeJS.ProcessEnv & { _applied?: boolean }
+  expand?: boolean
+}
+
 export async function loadNuxtConfig ({
   rootDir = '.',
   envConfig = {},
   configFile = defaultNuxtConfigFile,
   configContext = {},
   configOverrides = {},
-  createRequire = module => isJest ? _createRequire(module.filename) : jiti(module.filename)
-} = {}) {
+  createRequire = (module: NodeJS.Module) => isJest ? _createRequire(module.filename) : jiti(module.filename)
+}: LoadOptions = {}) {
   rootDir = path.resolve(rootDir)
 
   let options = {}
@@ -120,7 +129,7 @@ export async function loadNuxtConfig ({
   return options
 }
 
-function loadEnv (envConfig, rootDir = process.cwd()) {
+function loadEnv (envConfig: EnvConfig, rootDir = process.cwd()) {
   const env = Object.create(null)
 
   // Read dotenv
@@ -147,13 +156,13 @@ function loadEnv (envConfig, rootDir = process.cwd()) {
 }
 
 // Based on https://github.com/motdotla/dotenv-expand
-function expand (target, source = {}, parse = v => v) {
-  function getValue (key) {
+function expand (target: Record<string, string>, source: Record<string, string> = {}, parse = (v: string) => v) {
+  function getValue (key: string) {
     // Source value 'wins' over target value
     return source[key] !== undefined ? source[key] : target[key]
   }
 
-  function interpolate (value) {
+  function interpolate (value: string): string {
     if (typeof value !== 'string') {
       return value
     }
@@ -162,7 +171,8 @@ function expand (target, source = {}, parse = v => v) {
       const parts = /(.?)\${?([a-zA-Z0-9_:]+)?}?/g.exec(match)
       const prefix = parts[1]
 
-      let value, replacePart
+      let value: string
+      let replacePart: string
 
       if (prefix === '\\') {
         replacePart = parts[0]
diff --git a/packages/nuxt3/src/core/load.ts b/packages/nuxt3/src/core/load.ts
index 690ddc81d8..64d71b1da6 100644
--- a/packages/nuxt3/src/core/load.ts
+++ b/packages/nuxt3/src/core/load.ts
@@ -1,3 +1,4 @@
+import { EnvConfig } from 'nuxt/config/load'
 import { loadNuxtConfig } from '../config'
 import Nuxt from './nuxt'
 
@@ -8,7 +9,19 @@ const OVERRIDES = {
   start: { dev: false, _start: true }
 }
 
-export async function loadNuxt (loadOptions) {
+export interface LoadOptions {
+  for?: keyof typeof OVERRIDES
+  ready?: boolean
+
+  rootDir?: string
+  envConfig?: EnvConfig
+  configFile?: string
+  configContext?: {}
+  configOverrides?: {},
+  createRequire?: (module: NodeJS.Module) => NodeJS.Require
+}
+
+export async function loadNuxt (loadOptions: LoadOptions | LoadOptions['for']) {
   // Normalize loadOptions
   if (typeof loadOptions === 'string') {
     loadOptions = { for: loadOptions }
diff --git a/packages/nuxt3/src/core/module.ts b/packages/nuxt3/src/core/module.ts
index c130942f9e..c3a0418bc5 100644
--- a/packages/nuxt3/src/core/module.ts
+++ b/packages/nuxt3/src/core/module.ts
@@ -5,8 +5,24 @@ import consola from 'consola'
 
 import { chainFn, sequence } from 'nuxt/utils'
 
+import Nuxt from './nuxt'
+
+interface Module {
+  src: string
+  options: Record<string, any>
+  handler: () => any
+}
+
+interface Template {
+
+}
+
 export default class ModuleContainer {
-  constructor (nuxt) {
+  nuxt: Nuxt
+  options: Nuxt['options']
+  requiredModules: Record<string, Module>
+
+  constructor (nuxt: Nuxt) {
     this.nuxt = nuxt
     this.options = nuxt.options
     this.requiredModules = {}
@@ -83,7 +99,7 @@ export default class ModuleContainer {
     })
   }
 
-  addLayout (template, name) {
+  addLayout (template, name: string) {
     const { dst, src } = this.addTemplate(template)
     const layoutName = name || path.parse(src).name
     const layout = this.options.layouts[layoutName]
@@ -101,7 +117,7 @@ export default class ModuleContainer {
     }
   }
 
-  addErrorLayout (dst) {
+  addErrorLayout (dst: string) {
     const relativeBuildDir = path.relative(this.options.rootDir, this.options.buildDir)
     this.options.ErrorPage = `~/${relativeBuildDir}/${dst}`
   }
@@ -121,13 +137,13 @@ export default class ModuleContainer {
     )
   }
 
-  requireModule (moduleOpts) {
+  requireModule (moduleOpts: Module) {
     return this.addModule(moduleOpts)
   }
 
   async addModule (moduleOpts) {
     let src
-    let options
+    let options: Record<string, any>
     let handler
 
     // Type 1: String or Function
@@ -142,7 +158,7 @@ export default class ModuleContainer {
     }
 
     // Define handler if src is a function
-    if (typeof src === 'function') {
+    if (src instanceof Function) {
       handler = src
     }
 
diff --git a/packages/nuxt3/src/core/nuxt.ts b/packages/nuxt3/src/core/nuxt.ts
index 2cdd3160c2..8e61abb953 100644
--- a/packages/nuxt3/src/core/nuxt.ts
+++ b/packages/nuxt3/src/core/nuxt.ts
@@ -1,7 +1,7 @@
 
 import isPlainObject from 'lodash/isPlainObject'
 import consola from 'consola'
-import Hookable from 'hable'
+import Hookable from 'hookable'
 
 import { defineAlias } from 'nuxt/utils'
 import { getNuxtConfig } from 'nuxt/config'
@@ -13,6 +13,17 @@ import ModuleContainer from './module'
 import Resolver from './resolver'
 
 export default class Nuxt extends Hookable {
+  _ready?: Promise<this>
+  _initCalled?: boolean
+
+  options: any
+  resolver: Resolver
+  moduleContainer: ModuleContainer
+  server?: Server
+  renderer?: Server
+  render?: Server['app']
+  showReady?: () => void
+
   constructor (options = {}) {
     super(consola)
 
@@ -103,13 +114,14 @@ export default class Nuxt extends Hookable {
     defineAlias(this, this.server, ['renderRoute', 'renderAndGetWindow', 'listen'])
   }
 
-  async close (callback) {
+  async close (callback?: () => any | Promise<any>) {
     await this.callHook('close', this)
 
     if (typeof callback === 'function') {
       await callback()
     }
 
-    this.clearHooks()
+    // Deleting as no longer exists on `hookable`
+    // this.clearHooks()
   }
 }
diff --git a/packages/nuxt3/src/core/resolver.ts b/packages/nuxt3/src/core/resolver.ts
index e1c1bb4914..08adfdd50a 100644
--- a/packages/nuxt3/src/core/resolver.ts
+++ b/packages/nuxt3/src/core/resolver.ts
@@ -1,7 +1,7 @@
 import { resolve, join } from 'path'
 import fs from 'fs-extra'
-import consola from 'consola'
 
+import { Nuxt } from 'nuxt/core'
 import {
   startsWithRootAlias,
   startsWithSrcAlias,
@@ -9,8 +9,25 @@ import {
   clearRequireCache
 } from 'nuxt/utils'
 
+interface ResolvePathOptions {
+  isAlias?: boolean
+  isModule?: boolean
+  isStyle?: boolean
+}
+
+interface RequireModuleOptions {
+  useESM?: boolean
+  isAlias?: boolean
+  interopDefault?: any
+}
+
 export default class Resolver {
-  constructor (nuxt) {
+  _require: NodeJS.Require
+  _resolve: RequireResolve
+  nuxt: Nuxt
+  options: Nuxt['options']
+
+  constructor (nuxt: Nuxt) {
     this.nuxt = nuxt
     this.options = this.nuxt.options
 
@@ -26,7 +43,7 @@ export default class Resolver {
     this._resolve = require.resolve
   }
 
-  resolveModule (path) {
+  resolveModule (path: string) {
     try {
       return this._resolve(path, {
         paths: this.options.modulesDir
@@ -42,7 +59,7 @@ export default class Resolver {
     }
   }
 
-  resolveAlias (path) {
+  resolveAlias (path: string) {
     if (startsWithRootAlias(path)) {
       return join(this.options.rootDir, path.substr(2))
     }
@@ -54,21 +71,13 @@ export default class Resolver {
     return resolve(this.options.srcDir, path)
   }
 
-  resolvePath (path, { alias, isAlias = alias, module, isModule = module, isStyle } = {}) {
-    // TODO: Remove in Nuxt 3
-    if (alias) {
-      consola.warn('Using alias is deprecated and will be removed in Nuxt 3. Use `isAlias` instead.')
-    }
-    if (module) {
-      consola.warn('Using module is deprecated and will be removed in Nuxt 3. Use `isModule` instead.')
-    }
-
+  resolvePath (path: string, { isAlias, isModule, isStyle }: ResolvePathOptions = {}) {
     // Fast return in case of path exists
     if (fs.existsSync(path)) {
       return path
     }
 
-    let resolvedPath
+    let resolvedPath: string
 
     // Try to resolve it as a regular module
     if (isModule !== false) {
@@ -85,7 +94,7 @@ export default class Resolver {
       resolvedPath = path
     }
 
-    let isDirectory
+    let isDirectory: boolean
 
     // Check if resolvedPath exits and is not a directory
     if (fs.existsSync(resolvedPath)) {
@@ -119,22 +128,11 @@ export default class Resolver {
     throw new Error(`Cannot resolve "${path}" from "${resolvedPath}"`)
   }
 
-  requireModule (path, { esm, useESM = esm, alias, isAlias = alias, intropDefault, interopDefault = intropDefault } = {}) {
+  requireModule <T>(path: string, { useESM, isAlias, interopDefault }: RequireModuleOptions = {}): T {
     let resolvedPath = path
-    let requiredModule
+    let requiredModule: any
 
-    // TODO: Remove in Nuxt 3
-    if (intropDefault) {
-      consola.warn('Using intropDefault is deprecated and will be removed in Nuxt 3. Use `interopDefault` instead.')
-    }
-    if (alias) {
-      consola.warn('Using alias is deprecated and will be removed in Nuxt 3. Use `isAlias` instead.')
-    }
-    if (esm) {
-      consola.warn('Using esm is deprecated and will be removed in Nuxt 3. Use `useESM` instead.')
-    }
-
-    let lastError
+    let lastError: any
 
     // Try to resolve path
     try {
diff --git a/packages/nuxt3/src/generator/generator.ts b/packages/nuxt3/src/generator/generator.ts
index 9b3b79e45a..495c4d8ec0 100644
--- a/packages/nuxt3/src/generator/generator.ts
+++ b/packages/nuxt3/src/generator/generator.ts
@@ -6,10 +6,32 @@ import defu from 'defu'
 import htmlMinifier from 'html-minifier'
 import { parse } from 'node-html-parser'
 
+import type { Builder } from 'nuxt/builder'
+import type { Nuxt } from 'nuxt/core'
 import { isFullStatic, flatRoutes, isString, isUrl, promisifyRoute, waitFor, TARGETS } from 'nuxt/utils'
 
 export default class Generator {
-  constructor (nuxt, builder) {
+  _payload: null
+  setPayload: (payload: any) => void
+
+  builder?: Builder
+  isFullStatic: boolean
+  nuxt: Nuxt
+  options: Nuxt['options']
+  staticRoutes: string
+  srcBuiltPath: string
+  distPath: string
+  distNuxtPath: string
+
+  staticAssetsDir?: string
+  staticAssetsBase?: string
+
+  payloadDir?: string
+
+  routes: Array<{ route: string } & Record<string, any>>
+  generatedRoutes: Set<string>
+
+  constructor (nuxt: Nuxt, builder?: Builder) {
     this.nuxt = nuxt
     this.options = nuxt.options
     this.builder = builder
diff --git a/packages/nuxt3/src/generator/index.ts b/packages/nuxt3/src/generator/index.ts
index 6e420c7e35..da3052300c 100644
--- a/packages/nuxt3/src/generator/index.ts
+++ b/packages/nuxt3/src/generator/index.ts
@@ -1,6 +1,8 @@
+import type { Nuxt } from 'nuxt/core'
+
 import Generator from './generator'
 export { default as Generator } from './generator'
 
-export function getGenerator (nuxt) {
+export function getGenerator (nuxt: Nuxt) {
   return new Generator(nuxt)
 }
diff --git a/packages/nuxt3/src/server/context.ts b/packages/nuxt3/src/server/context.ts
index 99dc07c321..2e1f365cf6 100644
--- a/packages/nuxt3/src/server/context.ts
+++ b/packages/nuxt3/src/server/context.ts
@@ -1,5 +1,12 @@
+import { Server } from 'nuxt/server'
+
 export default class ServerContext {
-  constructor (server) {
+  nuxt: Server['nuxt']
+  globals: Server['globals']
+  options: Server['options']
+  resources: Server['resources']
+
+  constructor (server: Server) {
     this.nuxt = server.nuxt
     this.globals = server.globals
     this.options = server.options
diff --git a/packages/nuxt3/src/server/jsdom.ts b/packages/nuxt3/src/server/jsdom.ts
index f61a775b82..2d8cad2cc8 100644
--- a/packages/nuxt3/src/server/jsdom.ts
+++ b/packages/nuxt3/src/server/jsdom.ts
@@ -1,5 +1,11 @@
 import consola from 'consola'
-import { timeout } from 'nuxt/utils'
+import { DeterminedGlobals, timeout } from 'nuxt/utils'
+
+interface Options {
+  globals: DeterminedGlobals
+  loadedCallback: string
+  loadingTimeout?: number
+}
 
 export default async function renderAndGetWindow (
   url = 'http://localhost:3000',
@@ -8,7 +14,7 @@ export default async function renderAndGetWindow (
     loadedCallback,
     loadingTimeout = 2000,
     globals
-  } = {}
+  }: Options
 ) {
   const jsdom = await import('jsdom')
     .then(m => m.default || m)
@@ -27,13 +33,13 @@ export default async function renderAndGetWindow (
     resources: 'usable',
     runScripts: 'dangerously',
     virtualConsole: true,
-    beforeParse (window) {
+    beforeParse (window: Window) {
       // Mock window.scrollTo
       window.scrollTo = () => {}
     }
   }, jsdomOpts)
 
-  const jsdomErrHandler = (err) => {
+  const jsdomErrHandler = (err: any) => {
     throw err
   }
 
diff --git a/packages/nuxt3/src/server/listener.ts b/packages/nuxt3/src/server/listener.ts
index 125a566f6c..3560475c43 100644
--- a/packages/nuxt3/src/server/listener.ts
+++ b/packages/nuxt3/src/server/listener.ts
@@ -1,5 +1,6 @@
 import http from 'http'
 import https from 'https'
+import type { ListenOptions } from 'net'
 import enableDestroy from 'server-destroy'
 import ip from 'ip'
 import consola from 'consola'
@@ -8,6 +9,19 @@ import pify from 'pify'
 let RANDOM_PORT = '0'
 
 export default class Listener {
+  port: number | string
+  host: string
+  socket: string
+  https: boolean
+  app: any
+  dev: boolean
+  baseURL: string
+
+  listening: boolean
+  _server: null | http.Server
+  server: null | http.Server
+  address: null
+  url: null | string
   constructor ({ port, host, socket, https, app, dev, baseURL }) {
     // Options
     this.port = port
@@ -43,6 +57,9 @@ export default class Listener {
 
   computeURL () {
     const address = this.server.address()
+    if (typeof address === 'string') {
+      return address
+    }
     if (!this.socket) {
       switch (address.address) {
         case '127.0.0.1': this.host = 'localhost'; break
@@ -68,7 +85,7 @@ export default class Listener {
 
     // Call server.listen
     // Prepare listenArgs
-    const listenArgs = this.socket ? { path: this.socket } : { host: this.host, port: this.port }
+    const listenArgs: ListenOptions = this.socket ? { path: this.socket } : { host: this.host, port: Number(this.port) }
     listenArgs.exclusive = false
 
     // Call server.listen
diff --git a/packages/nuxt3/src/server/middleware/timing.ts b/packages/nuxt3/src/server/middleware/timing.ts
index 5c62c02868..f510a4b223 100644
--- a/packages/nuxt3/src/server/middleware/timing.ts
+++ b/packages/nuxt3/src/server/middleware/timing.ts
@@ -1,8 +1,11 @@
+import type { ServerResponse } from 'http'
+import type { IncomingMessage } from 'connect'
+
 import consola from 'consola'
 import onHeaders from 'on-headers'
 import { Timer } from 'nuxt/utils'
 
-export default options => (req, res, next) => {
+export default options => (_req: IncomingMessage, res: ServerResponse & { timing?: ServerTiming }, next: (err?: any) => void) => {
   if (res.timing) {
     consola.warn('server-timing is already registered.')
   }
@@ -31,13 +34,15 @@ export default options => (req, res, next) => {
 }
 
 class ServerTiming extends Timer {
-  constructor (...args) {
-    super(...args)
+  headers: string[]
+
+  constructor () {
+    super()
     this.headers = []
   }
 
-  end (...args) {
-    const time = super.end(...args)
+  end (name?: string) {
+    const time = super.end(name)
     if (time) {
       this.headers.push(this.formatHeader(time))
     }
@@ -49,7 +54,7 @@ class ServerTiming extends Timer {
     this.headers.length = 0
   }
 
-  formatHeader (time) {
+  formatHeader (time: ReturnType<Timer['end']>) {
     const desc = time.description ? `;desc="${time.description}"` : ''
     return `${time.name};dur=${time.duration}${desc}`
   }
diff --git a/packages/nuxt3/src/server/server.ts b/packages/nuxt3/src/server/server.ts
index 2019c04962..19c0c7f2c2 100644
--- a/packages/nuxt3/src/server/server.ts
+++ b/packages/nuxt3/src/server/server.ts
@@ -1,10 +1,14 @@
 import path from 'path'
+import { ServerResponse } from 'http'
 import consola from 'consola'
 import launchMiddleware from 'launch-editor-middleware'
 import serveStatic from 'serve-static'
 import servePlaceholder from 'serve-placeholder'
-import connect from 'connect'
-import { determineGlobals, isUrl } from 'nuxt/utils'
+import connect, { IncomingMessage } from 'connect'
+import type { TemplateExecutor } from 'lodash'
+
+import { Nuxt } from 'nuxt/core'
+import { DeterminedGlobals, determineGlobals, isUrl } from 'nuxt/utils'
 import { VueRenderer } from 'nuxt/vue-renderer'
 
 import ServerContext from './context'
@@ -14,8 +18,34 @@ import errorMiddleware from './middleware/error'
 import Listener from './listener'
 import createTimingMiddleware from './middleware/timing'
 
+interface Manifest {
+  assetsMapping: Record<string, string[]>
+  publicPath: string
+}
+
 export default class Server {
-  constructor (nuxt) {
+  __closed?: boolean
+  _readyCalled?: boolean
+
+  app: connect.Server
+  devMiddleware: (req: IncomingMessage, res: ServerResponse, next: (err?: any) => void) => any
+  listeners: Listener[]
+  nuxt: Nuxt
+  globals: DeterminedGlobals
+  options: Nuxt['options']
+  publicPath: boolean
+  renderer: VueRenderer
+  resources: {
+    clientManifest?: Manifest
+    modernManifest?: Manifest
+    serverManifest?: Manifest
+    ssrTemplate?: TemplateExecutor
+    spaTemplate?: TemplateExecutor
+    errorTemplate?: TemplateExecutor
+  }
+  serverContext: ServerContext
+
+  constructor (nuxt: Nuxt) {
     this.nuxt = nuxt
     this.options = nuxt.options
 
@@ -76,7 +106,7 @@ export default class Server {
       const { compressor } = this.options.render
       if (typeof compressor === 'object') {
         // If only setting for `compression` are provided, require the module and insert
-        const compression = this.nuxt.resolver.requireModule('compression')
+        const compression = this.nuxt.resolver.requireModule<typeof import('compression')>('compression')
         this.useMiddleware(compression(compressor))
       } else if (compressor) {
         // Else, require own compression middleware if compressor is actually truthy
@@ -317,12 +347,12 @@ export default class Server {
     return this.app.stack.map(({ handle }) => handle._middleware && handle._middleware.entry).filter(Boolean)
   }
 
-  renderRoute () {
-    return this.renderer.renderRoute.apply(this.renderer, arguments)
+  renderRoute (...args: Parameters<VueRenderer['renderRoute']>) {
+    return this.renderer.renderRoute.apply(this.renderer, ...args.slice())
   }
 
-  loadResources () {
-    return this.renderer.loadResources.apply(this.renderer, arguments)
+  loadResources (...args: Parameters<VueRenderer['loadResources']>) {
+    return this.renderer.loadResources.apply(this.renderer, ...args)
   }
 
   renderAndGetWindow (url, opts = {}, {
@@ -337,13 +367,13 @@ export default class Server {
     })
   }
 
-  async listen (port, host, socket) {
+  async listen (port?: string | number, host?: string, socket?: string) {
     // Ensure nuxt is ready
     await this.nuxt.ready()
 
     // Create a new listener
     const listener = new Listener({
-      port: isNaN(parseInt(port)) ? this.options.server.port : port,
+      port: typeof port !== 'number' && isNaN(parseInt(port)) ? this.options.server.port : port,
       host: host || this.options.server.host,
       socket: socket || this.options.server.socket,
       https: this.options.server.https,
diff --git a/packages/nuxt3/src/utils/cjs.ts b/packages/nuxt3/src/utils/cjs.ts
index d294ff70a4..743af42823 100644
--- a/packages/nuxt3/src/utils/cjs.ts
+++ b/packages/nuxt3/src/utils/cjs.ts
@@ -1,10 +1,10 @@
 import { join } from 'path'
 
-export function isExternalDependency (id) {
+export function isExternalDependency (id: string) {
   return /[/\\]node_modules[/\\]/.test(id)
 }
 
-export function clearRequireCache (id) {
+export function clearRequireCache (id: string) {
   if (isExternalDependency(id)) {
     return
   }
@@ -27,7 +27,7 @@ export function clearRequireCache (id) {
   delete require.cache[id]
 }
 
-export function scanRequireTree (id, files = new Set()) {
+export function scanRequireTree (id: string, files = new Set<string>()) {
   if (isExternalDependency(id) || files.has(id)) {
     return files
   }
@@ -48,20 +48,20 @@ export function scanRequireTree (id, files = new Set()) {
   return files
 }
 
-export function getRequireCacheItem (id) {
+export function getRequireCacheItem (id: string) {
   try {
     return require.cache[id]
   } catch (e) {
   }
 }
 
-export function tryRequire (id) {
+export function tryRequire (id: string) {
   try {
     return require(id)
   } catch (e) {
   }
 }
 
-export function getPKG (id) {
+export function getPKG (id: string) {
   return tryRequire(join(id, 'package.json'))
 }
diff --git a/packages/nuxt3/src/utils/constants.ts b/packages/nuxt3/src/utils/constants.ts
index 1af82f818c..9195fd516f 100644
--- a/packages/nuxt3/src/utils/constants.ts
+++ b/packages/nuxt3/src/utils/constants.ts
@@ -1,9 +1,13 @@
 export const TARGETS = {
   server: 'server',
   static: 'static'
-}
+} as const
+
+export type Target = keyof typeof TARGETS
 
 export const MODES = {
   universal: 'universal',
   spa: 'spa'
-}
+} as const
+
+export type Mode = keyof typeof MODES
\ No newline at end of file
diff --git a/packages/nuxt3/src/utils/context.ts b/packages/nuxt3/src/utils/context.ts
index 9399809b9f..fc4d989e2b 100644
--- a/packages/nuxt3/src/utils/context.ts
+++ b/packages/nuxt3/src/utils/context.ts
@@ -1,19 +1,35 @@
+import type { ServerResponse } from 'http'
+import type { IncomingMessage } from 'connect'
+
 import { TARGETS } from './constants'
 
-export const getContext = function getContext (req, res) {
+export const getContext = function getContext (req: IncomingMessage, res: ServerResponse) {
   return { req, res }
 }
 
-export const determineGlobals = function determineGlobals (globalName, globals) {
-  const _globals = {}
+type NuxtGlobal = string | ((globalName: string) => string)
+
+type Globals = 'id' | 'nuxt' | 'context' | 'pluginPrefix' | 'readyCallback' | 'loadedCallback'
+
+type NuxtGlobals = {
+  [key in Globals]: NuxtGlobal
+}
+
+export type DeterminedGlobals = {
+  [key in keyof NuxtGlobals]: string
+}
+
+export const determineGlobals = function determineGlobals (globalName: string, globals: NuxtGlobals) {
+  const _globals: Partial<DeterminedGlobals> = {}
   for (const global in globals) {
-    if (typeof globals[global] === 'function') {
-      _globals[global] = globals[global](globalName)
+    const currentGlobal = globals[global]
+    if (currentGlobal instanceof Function) {
+      _globals[global] = currentGlobal(globalName)
     } else {
-      _globals[global] = globals[global]
+      _globals[global] = currentGlobal
     }
   }
-  return _globals
+  return _globals as DeterminedGlobals
 }
 
 export const isFullStatic = function (options) {
diff --git a/packages/nuxt3/src/utils/lang.ts b/packages/nuxt3/src/utils/lang.ts
index 7ecf3fee94..f9882823ec 100644
--- a/packages/nuxt3/src/utils/lang.ts
+++ b/packages/nuxt3/src/utils/lang.ts
@@ -1,20 +1,25 @@
-export const encodeHtml = function encodeHtml (str) {
+export const encodeHtml = function encodeHtml (str: string) {
   return str.replace(/</g, '&lt;').replace(/>/g, '&gt;')
 }
 
-export const isString = obj => typeof obj === 'string' || obj instanceof String
+export const isString = (obj: unknown): obj is string =>
+  typeof obj === 'string' || obj instanceof String
 
-export const isNonEmptyString = obj => Boolean(obj && isString(obj))
+export const isNonEmptyString = (obj: unknown): obj is string =>
+  Boolean(obj && isString(obj))
 
-export const isPureObject = obj => !Array.isArray(obj) && typeof obj === 'object'
+export const isPureObject = (
+  obj: unknown
+): obj is Exclude<object, Array<any>> =>
+  !Array.isArray(obj) && typeof obj === 'object'
 
-export const isUrl = function isUrl (url) {
+export const isUrl = function isUrl (url: string) {
   return ['http', '//'].some(str => url.startsWith(str))
 }
 
-export const urlJoin = function urlJoin () {
+export const urlJoin = function urlJoin (...args: string[]) {
   return [].slice
-    .call(arguments)
+    .call(args)
     .join('/')
     .replace(/\/+/g, '/')
     .replace(':/', '://')
@@ -22,13 +27,11 @@ export const urlJoin = function urlJoin () {
 
 /**
  * Wraps value in array if it is not already an array
- *
- * @param  {any} value
- * @return {array}
  */
-export const wrapArray = value => Array.isArray(value) ? value : [value]
+export const wrapArray = <T>(value: T | T[]): T[] =>
+  Array.isArray(value) ? value : [value]
 
-const WHITESPACE_REPLACEMENTS = [
+const WHITESPACE_REPLACEMENTS: [RegExp, string][] = [
   [/[ \t\f\r]+\n/g, '\n'], // strip empty indents
   [/{\n{2,}/g, '{\n'], // strip start padding from blocks
   [/\n{2,}([ \t\f\r]*})/g, '\n$1'], // strip end padding from blocks
@@ -36,7 +39,7 @@ const WHITESPACE_REPLACEMENTS = [
   [/\n{2,}$/g, '\n'] // strip blank lines EOF (0 allowed)
 ]
 
-export const stripWhitespace = function stripWhitespace (string) {
+export const stripWhitespace = function stripWhitespace (string: string) {
   WHITESPACE_REPLACEMENTS.forEach(([regex, newSubstr]) => {
     string = string.replace(regex, newSubstr)
   })
diff --git a/packages/nuxt3/src/utils/locking.ts b/packages/nuxt3/src/utils/locking.ts
index 9380a53c47..f976586e8a 100644
--- a/packages/nuxt3/src/utils/locking.ts
+++ b/packages/nuxt3/src/utils/locking.ts
@@ -2,27 +2,42 @@ import path from 'path'
 import consola from 'consola'
 import hash from 'hash-sum'
 import fs from 'fs-extra'
-import properlock from 'proper-lockfile'
+import properlock, { LockOptions } from 'proper-lockfile'
 import onExit from 'signal-exit'
 
-export const lockPaths = new Set()
+export const lockPaths = new Set<string>()
 
-export const defaultLockOptions = {
+export const defaultLockOptions: Required<
+  Pick<LockOptions, 'stale' | 'onCompromised'>
+> = {
   stale: 30000,
   onCompromised: err => consola.warn(err)
 }
 
-export function getLockOptions (options) {
+export function getLockOptions (options: Partial<LockOptions>) {
   return Object.assign({}, defaultLockOptions, options)
 }
 
-export function createLockPath ({ id = 'nuxt', dir, root }) {
+interface NuxtLockOptions {
+  id?: string
+  dir: string
+  root: string
+  options?: LockOptions
+}
+
+export function createLockPath ({
+  id = 'nuxt',
+  dir,
+  root
+}: Pick<NuxtLockOptions, 'id' | 'dir' | 'root'>) {
   const sum = hash(`${root}-${dir}`)
 
   return path.resolve(root, 'node_modules/.cache/nuxt', `${id}-lock-${sum}`)
 }
 
-export async function getLockPath (config) {
+export async function getLockPath (
+  config: Pick<NuxtLockOptions, 'id' | 'dir' | 'root'>
+) {
   const lockPath = createLockPath(config)
 
   // the lock is created for the lockPath as ${lockPath}.lock
@@ -32,8 +47,12 @@ export async function getLockPath (config) {
   return lockPath
 }
 
-export async function lock ({ id, dir, root, options }) {
-  const lockPath = await getLockPath({ id, dir, root })
+export async function lock ({ id, dir, root, options }: NuxtLockOptions) {
+  const lockPath = await getLockPath({
+    id,
+    dir,
+    root
+  })
 
   try {
     const locked = await properlock.check(lockPath)
@@ -45,7 +64,7 @@ export async function lock ({ id, dir, root, options }) {
   }
 
   let lockWasCompromised = false
-  let release
+  let release: (() => Promise<void>) | undefined
 
   try {
     options = getLockOptions(options)
@@ -94,7 +113,7 @@ export async function lock ({ id, dir, root, options }) {
       // as well, but in our case its much more likely the lock was
       // compromised due to mtime update timeouts
       const lockDir = `${lockPath}.lock`
-      if (await fs.exists(lockDir)) {
+      if (await fs.pathExists(lockDir)) {
         await fs.remove(lockDir)
       }
     }
diff --git a/packages/nuxt3/src/utils/modern.ts b/packages/nuxt3/src/utils/modern.ts
index a080a5d7d6..12cdc18d75 100644
--- a/packages/nuxt3/src/utils/modern.ts
+++ b/packages/nuxt3/src/utils/modern.ts
@@ -1,4 +1,7 @@
-import UAParser from 'ua-parser-js'
+import { UAParser } from 'ua-parser-js'
+
+import type { SemVer } from 'semver'
+import type { IncomingMessage } from 'connect'
 
 export const ModernBrowsers = {
   Edge: '16',
@@ -12,49 +15,65 @@ export const ModernBrowsers = {
   Yandex: '18',
   Vivaldi: '1.14',
   'Mobile Safari': '10.3'
-}
+} as const
 
-let semver
-let __modernBrowsers
+type ModernBrowsers = { -readonly [key in keyof typeof ModernBrowsers]: SemVer }
+
+let semver: typeof import('semver')
+let __modernBrowsers: ModernBrowsers
 
 const getModernBrowsers = () => {
   if (__modernBrowsers) {
     return __modernBrowsers
   }
 
-  __modernBrowsers = Object.keys(ModernBrowsers)
-    .reduce((allBrowsers, browser) => {
-      allBrowsers[browser] = semver.coerce(ModernBrowsers[browser])
+  __modernBrowsers = (Object.keys(ModernBrowsers) as Array<
+    keyof typeof ModernBrowsers
+  >).reduce(
+    (allBrowsers, browser) => {
+      const version = semver.coerce(ModernBrowsers[browser])
+      if (version) { allBrowsers[browser] = version }
       return allBrowsers
-    }, {})
+    },
+    {} as ModernBrowsers
+  )
   return __modernBrowsers
 }
 
-export const isModernBrowser = (ua) => {
+interface NuxtRequest extends IncomingMessage {
+  socket: IncomingMessage['socket'] & {
+    _modern?: boolean
+  }
+}
+
+export const isModernBrowser = (ua: string) => {
   if (!ua) {
     return false
   }
   if (!semver) {
     semver = require('semver')
   }
-  const { browser } = UAParser(ua)
+  const browser = new UAParser(ua).getBrowser()
   const browserVersion = semver.coerce(browser.version)
   if (!browserVersion) {
     return false
   }
   const modernBrowsers = getModernBrowsers()
-  return Boolean(modernBrowsers[browser.name] && semver.gte(browserVersion, modernBrowsers[browser.name]))
+  const name = browser.name as keyof typeof modernBrowsers
+  return Boolean(
+    name && name in modernBrowsers && semver.gte(browserVersion, modernBrowsers[name])
+  )
 }
 
-export const isModernRequest = (req, modernMode = false) => {
+export const isModernRequest = (req: NuxtRequest, modernMode = false) => {
   if (modernMode === false) {
     return false
   }
 
-  const { socket = {}, headers } = req
+  const { socket = {} as NuxtRequest['socket'], headers } = req
   if (socket._modern === undefined) {
     const ua = headers && headers['user-agent']
-    socket._modern = isModernBrowser(ua)
+    socket._modern = ua && isModernBrowser(ua)
   }
 
   return socket._modern
diff --git a/packages/nuxt3/src/utils/resolve.ts b/packages/nuxt3/src/utils/resolve.ts
index 4a54c6cfba..dcdceed509 100644
--- a/packages/nuxt3/src/utils/resolve.ts
+++ b/packages/nuxt3/src/utils/resolve.ts
@@ -2,7 +2,8 @@ import path from 'path'
 import consola from 'consola'
 import escapeRegExp from 'lodash/escapeRegExp'
 
-export const startsWithAlias = aliasArray => str => aliasArray.some(c => str.startsWith(c))
+export const startsWithAlias = (aliasArray: string[]) => (str: string) =>
+  aliasArray.some(c => str.startsWith(c))
 
 export const startsWithSrcAlias = startsWithAlias(['@', '~'])
 
@@ -24,9 +25,9 @@ export const wChunk = function wChunk (p = '') {
 
 const reqSep = /\//g
 const sysSep = escapeRegExp(path.sep)
-const normalize = string => string.replace(reqSep, sysSep)
+const normalize = (string: string) => string.replace(reqSep, sysSep)
 
-export const r = function r (...args) {
+export const r = function r (...args: string[]) {
   const lastArg = args[args.length - 1]
 
   if (startsWithSrcAlias(lastArg)) {
@@ -36,14 +37,12 @@ export const r = function r (...args) {
   return wp(path.resolve(...args.map(normalize)))
 }
 
-export const relativeTo = function relativeTo (...args) {
-  const dir = args.shift()
-
+export const relativeTo = function relativeTo (dir: string, ...args: string[]): string {
   // Keep webpack inline loader intact
   if (args[0].includes('!')) {
-    const loaders = args.shift().split('!')
+    const loaders = args.shift()!.split('!')
 
-    return loaders.concat(relativeTo(dir, loaders.pop(), ...args)).join('!')
+    return loaders.concat(relativeTo(dir, loaders.pop()!, ...args)).join('!')
   }
 
   // Resolve path
@@ -63,7 +62,17 @@ export const relativeTo = function relativeTo (...args) {
   return wp(rp)
 }
 
-export function defineAlias (src, target, prop, opts = {}) {
+interface AliasOptions {
+  bind?: boolean
+  warn?: boolean
+}
+
+export function defineAlias (
+  src: string,
+  target: Record<string, any>,
+  prop: string | string[],
+  opts: AliasOptions = {}
+) {
   const { bind = true, warn = false } = opts
 
   if (Array.isArray(prop)) {
@@ -94,9 +103,9 @@ export function defineAlias (src, target, prop, opts = {}) {
   })
 }
 
-const isIndex = s => /(.*)\/index\.[^/]+$/.test(s)
+const isIndex = (s: string) => /(.*)\/index\.[^/]+$/.test(s)
 
-export function isIndexFileAndFolder (pluginFiles) {
+export function isIndexFileAndFolder (pluginFiles: string[]) {
   // Return early in case the matching file count exceeds 2 (index.js + folder)
   if (pluginFiles.length !== 2) {
     return false
@@ -105,5 +114,9 @@ export function isIndexFileAndFolder (pluginFiles) {
 }
 
 export const getMainModule = () => {
-  return require.main || (module && module.main) || module
+  return (
+    require.main ||
+    (module && ((module as any).main as NodeJS.Module)) ||
+    module
+  )
 }
diff --git a/packages/nuxt3/src/utils/route.ts b/packages/nuxt3/src/utils/route.ts
index 95dc8f238e..f02f559b3c 100644
--- a/packages/nuxt3/src/utils/route.ts
+++ b/packages/nuxt3/src/utils/route.ts
@@ -2,9 +2,12 @@ import path from 'path'
 import get from 'lodash/get'
 import consola from 'consola'
 
+import type { Component } from 'vue'
+import type { _RouteRecordBase } from 'vue-router'
+
 import { r } from './resolve'
 
-export const flatRoutes = function flatRoutes (router, fileName = '', routes = []) {
+export const flatRoutes = function flatRoutes (router, fileName = '', routes: string[] = []) {
   router.forEach((r) => {
     if ([':', '*'].some(c => r.path.includes(c))) {
       return
@@ -30,12 +33,12 @@ export const flatRoutes = function flatRoutes (router, fileName = '', routes = [
   return routes
 }
 
-function cleanChildrenRoutes (routes, isChild = false, routeNameSplitter = '-') {
+function cleanChildrenRoutes (routes: NuxtRouteConfig[], isChild = false, routeNameSplitter = '-') {
   let start = -1
   const regExpIndex = new RegExp(`${routeNameSplitter}index$`)
-  const routesIndex = []
+  const routesIndex: string[][] = []
   routes.forEach((route) => {
-    if (regExpIndex.test(route.name) || route.name === 'index') {
+    if (route.name && typeof route.name === 'string' && (regExpIndex.test(route.name) || route.name === 'index')) {
       // Save indexOf 'index' key in name
       const res = route.name.split(routeNameSplitter)
       const s = res.indexOf('index')
@@ -46,7 +49,7 @@ function cleanChildrenRoutes (routes, isChild = false, routeNameSplitter = '-')
   routes.forEach((route) => {
     route.path = isChild ? route.path.replace('/', '') : route.path
     if (route.path.includes('?')) {
-      const names = route.name.split(routeNameSplitter)
+      const names =  typeof route.name === 'string' && route.name.split(routeNameSplitter) || []
       const paths = route.path.split('/')
       if (!isChild) {
         paths.shift()
@@ -66,7 +69,9 @@ function cleanChildrenRoutes (routes, isChild = false, routeNameSplitter = '-')
       })
       route.path = (isChild ? '' : '/') + paths.join('/')
     }
-    route.name = route.name.replace(regExpIndex, '')
+    if (route.name) {
+      route.name = typeof route.name === 'string' && route.name.replace(regExpIndex, '')
+    }
     if (route.children) {
       if (route.children.find(child => child.path === '')) {
         delete route.name
@@ -79,7 +84,7 @@ function cleanChildrenRoutes (routes, isChild = false, routeNameSplitter = '-')
 
 const DYNAMIC_ROUTE_REGEX = /^\/([:*])/
 
-export const sortRoutes = function sortRoutes (routes) {
+export const sortRoutes = function sortRoutes (routes: NuxtRouteConfig[]) {
   routes.sort((a, b) => {
     if (!a.path.length) {
       return -1
@@ -136,6 +141,22 @@ export const sortRoutes = function sortRoutes (routes) {
   return routes
 }
 
+interface CreateRouteOptions {
+  files: string[]
+  srcDir: string
+  pagesDir?: string
+  routeNameSplitter?: string
+  supportedExtensions?: string[]
+  trailingSlash: boolean
+}
+
+interface NuxtRouteConfig extends Omit<_RouteRecordBase, 'children'> {
+  component?: Component | string
+  chunkName?: string
+  pathToRegexpOptions?: any
+  children?: NuxtRouteConfig[]
+}
+
 export const createRoutes = function createRoutes ({
   files,
   srcDir,
@@ -143,8 +164,8 @@ export const createRoutes = function createRoutes ({
   routeNameSplitter = '-',
   supportedExtensions = ['vue', 'js'],
   trailingSlash
-}) {
-  const routes = []
+}: CreateRouteOptions) {
+  const routes: NuxtRouteConfig[] = []
   files.forEach((file) => {
     const keys = file
       .replace(new RegExp(`^${pagesDir}`), '')
@@ -152,13 +173,13 @@ export const createRoutes = function createRoutes ({
       .replace(/\/{2,}/g, '/')
       .split('/')
       .slice(1)
-    const route = { name: '', path: '', component: r(srcDir, file) }
+    const route: NuxtRouteConfig = { name: '', path: '', component: r(srcDir, file) }
     let parent = routes
     keys.forEach((key, i) => {
       // remove underscore only, if its the prefix
       const sanitizedKey = key.startsWith('_') ? key.substr(1) : key
 
-      route.name = route.name
+      route.name = route.name && typeof route.name === 'string'
         ? route.name + routeNameSplitter + sanitizedKey
         : sanitizedKey
       route.name += key === '_' ? 'all' : ''
@@ -192,9 +213,9 @@ export const createRoutes = function createRoutes ({
 }
 
 // Guard dir1 from dir2 which can be indiscriminately removed
-export const guardDir = function guardDir (options, key1, key2) {
-  const dir1 = get(options, key1, false)
-  const dir2 = get(options, key2, false)
+export const guardDir = function guardDir (options: Record<string, unknown>, key1: string, key2: string) {
+  const dir1 = get(options, key1, false) as string
+  const dir2 = get(options, key2, false) as string
 
   if (
     dir1 &&
@@ -213,7 +234,7 @@ export const guardDir = function guardDir (options, key1, key2) {
   }
 }
 
-const getRoutePathExtension = (key) => {
+const getRoutePathExtension = (key: string) => {
   if (key === '_') {
     return '*'
   }
diff --git a/packages/nuxt3/src/utils/serialize.ts b/packages/nuxt3/src/utils/serialize.ts
index f1b2ebdf09..d2ea21ebca 100644
--- a/packages/nuxt3/src/utils/serialize.ts
+++ b/packages/nuxt3/src/utils/serialize.ts
@@ -1,6 +1,10 @@
 import serialize from 'serialize-javascript'
 
-export function normalizeFunctions (obj) {
+export function normalizeFunctions (obj: Array<any>): Array<any>
+export function normalizeFunctions (obj: null): null
+export function normalizeFunctions (obj: Function): Function
+export function normalizeFunctions (obj: Record<string, any>): Record<string, any>
+export function normalizeFunctions (obj: Array<unknown> | null | Function | Record<string, any>) {
   if (typeof obj !== 'object' || Array.isArray(obj) || obj === null) {
     return obj
   }
@@ -22,14 +26,14 @@ export function normalizeFunctions (obj) {
           functionBody = `return ${functionBody}`
         }
         // eslint-disable-next-line no-new-func
-        obj[key] = new Function(...match[1].split(',').map(arg => arg.trim()), functionBody)
+        obj[key] = new Function(...match[1].split(',').map((arg: string) => arg.trim()), functionBody)
       }
     }
   }
   return obj
 }
 
-export function serializeFunction (func) {
+export function serializeFunction (func: Function) {
   let open = false
   func = normalizeFunctions(func)
   return serialize(func)
diff --git a/packages/nuxt3/src/utils/task.ts b/packages/nuxt3/src/utils/task.ts
index a6a82995c8..64e71576d6 100644
--- a/packages/nuxt3/src/utils/task.ts
+++ b/packages/nuxt3/src/utils/task.ts
@@ -1,11 +1,17 @@
-export const sequence = function sequence (tasks, fn) {
+export const sequence = function sequence<T, R> (
+  tasks: T[],
+  fn: (task: T) => R
+) {
   return tasks.reduce(
-    (promise, task) => promise.then(() => fn(task)),
+    (promise, task): any => promise.then(() => fn(task)),
     Promise.resolve()
   )
 }
 
-export const parallel = function parallel (tasks, fn) {
+export const parallel = function parallel<T, R> (
+  tasks: T[],
+  fn: (task: T) => R
+) {
   return Promise.all(tasks.map(fn))
 }
 
diff --git a/packages/nuxt3/src/utils/timer.ts b/packages/nuxt3/src/utils/timer.ts
index 2add0401af..760de0d6f3 100644
--- a/packages/nuxt3/src/utils/timer.ts
+++ b/packages/nuxt3/src/utils/timer.ts
@@ -1,5 +1,8 @@
-async function promiseFinally (fn, finalFn) {
-  let result
+async function promiseFinally<T> (
+  fn: (() => Promise<T>) | Promise<T>,
+  finalFn: () => any
+) {
+  let result: T
   try {
     if (typeof fn === 'function') {
       result = await fn()
@@ -12,8 +15,12 @@ async function promiseFinally (fn, finalFn) {
   return result
 }
 
-export const timeout = function timeout (fn, ms, msg) {
-  let timerId
+export const timeout = function timeout (
+  fn: () => any,
+  ms: number,
+  msg: string
+) {
+  let timerId: NodeJS.Timeout
   const warpPromise = promiseFinally(fn, () => clearTimeout(timerId))
   const timerPromise = new Promise((resolve, reject) => {
     timerId = setTimeout(() => reject(new Error(msg)), ms)
@@ -21,16 +28,25 @@ export const timeout = function timeout (fn, ms, msg) {
   return Promise.race([warpPromise, timerPromise])
 }
 
-export const waitFor = function waitFor (ms) {
+export const waitFor = function waitFor (ms: number) {
   return new Promise(resolve => setTimeout(resolve, ms || 0))
 }
+
+interface Time {
+  name: string
+  description: string
+  start: [number, number] | bigint
+  duration?: bigint | [number, number]
+}
 export class Timer {
+  _times: Map<string, Time>
+
   constructor () {
     this._times = new Map()
   }
 
-  start (name, description) {
-    const time = {
+  start (name: string, description: string) {
+    const time: Time = {
       name,
       description,
       start: this.hrtime()
@@ -39,22 +55,33 @@ export class Timer {
     return time
   }
 
-  end (name) {
+  end (name: string) {
     if (this._times.has(name)) {
-      const time = this._times.get(name)
-      time.duration = this.hrtime(time.start)
+      const time = this._times.get(name)!
+      if (typeof time.start === 'bigint') {
+        time.duration = this.hrtime(time.start)
+      } else {
+        time.duration = this.hrtime(time.start)
+      }
       this._times.delete(name)
       return time
     }
   }
 
-  hrtime (start) {
+  hrtime (start?: bigint): bigint
+  hrtime (start?: [number, number]): [number, number]
+  hrtime (start?: [number, number] | bigint) {
     const useBigInt = typeof process.hrtime.bigint === 'function'
     if (start) {
-      const end = useBigInt ? process.hrtime.bigint() : process.hrtime(start)
-      return useBigInt
-        ? (end - start) / BigInt(1000000)
-        : (end[0] * 1e3) + (end[1] * 1e-6)
+      if (typeof start === 'bigint') {
+        if (!useBigInt) { throw new Error('bigint is not supported.') }
+
+        const end = process.hrtime.bigint()
+        return (end - start) / BigInt(1000000)
+      }
+
+      const end = process.hrtime(start)
+      return end[0] * 1e3 + end[1] * 1e-6
     }
     return useBigInt ? process.hrtime.bigint() : process.hrtime()
   }
diff --git a/packages/nuxt3/src/vue-renderer/renderer.ts b/packages/nuxt3/src/vue-renderer/renderer.ts
index d9ee549950..d6eee18d32 100644
--- a/packages/nuxt3/src/vue-renderer/renderer.ts
+++ b/packages/nuxt3/src/vue-renderer/renderer.ts
@@ -7,9 +7,22 @@ import { TARGETS, isModernRequest, waitFor } from 'nuxt/utils'
 import SPARenderer from './renderers/spa'
 import SSRRenderer from './renderers/ssr'
 import ModernRenderer from './renderers/modern'
+import ServerContext from 'nuxt/server/context'
 
 export default class VueRenderer {
-  constructor (context) {
+  __closed?: boolean
+  _state?: 'created' | 'loading' | 'ready' | 'error'
+  _error?: null
+  _readyPromise?: Promise<any>
+  distPath: string
+  serverContext: ServerContext
+  renderer: {
+    ssr: any
+    modern: any
+    spa: any
+  }
+
+  constructor (context: ServerContext) {
     this.serverContext = context
     this.options = this.serverContext.options
 
@@ -86,10 +99,10 @@ export default class VueRenderer {
     }
   }
 
-  async loadResources (_fs) {
+  async loadResources (_fs: typeof import('fs-extra')) {
     const updated = []
 
-    const readResource = async (fileName, encoding) => {
+    const readResource = async (fileName: string, encoding: string) => {
       try {
         const fullPath = path.resolve(this.distPath, fileName)
 
@@ -311,16 +324,16 @@ export default class VueRenderer {
     return {
       clientManifest: {
         fileName: 'client.manifest.json',
-        transform: src => JSON.parse(src)
+        transform: (src: string) => JSON.parse(src)
       },
       modernManifest: {
         fileName: 'modern.manifest.json',
-        transform: src => JSON.parse(src)
+        transform: (src: string) => JSON.parse(src)
       },
       serverManifest: {
         fileName: 'server.manifest.json',
         // BundleRenderer needs resolved contents
-        transform: async (src, { readResource }) => {
+        transform: async (src: string, { readResource }) => {
           const serverManifest = JSON.parse(src)
 
           const readResources = async (obj) => {
@@ -357,16 +370,16 @@ export default class VueRenderer {
       },
       ssrTemplate: {
         fileName: 'index.ssr.html',
-        transform: src => this.parseTemplate(src)
+        transform: (src: string) => this.parseTemplate(src)
       },
       spaTemplate: {
         fileName: 'index.spa.html',
-        transform: src => this.parseTemplate(src)
+        transform: (src: string) => this.parseTemplate(src)
       }
     }
   }
 
-  parseTemplate (templateStr) {
+  parseTemplate (templateStr: string) {
     return template(templateStr, {
       interpolate: /{{([\s\S]+?)}}/g,
       evaluate: /{%([\s\S]+?)%}/g
diff --git a/packages/nuxt3/src/vue-renderer/renderers/base.ts b/packages/nuxt3/src/vue-renderer/renderers/base.ts
index ad1d3e3def..693fd5cb28 100644
--- a/packages/nuxt3/src/vue-renderer/renderers/base.ts
+++ b/packages/nuxt3/src/vue-renderer/renderers/base.ts
@@ -1,10 +1,15 @@
+import ServerContext from "nuxt/server/context"
+
 export default class BaseRenderer {
-  constructor (serverContext) {
+  serverContext: ServerContext
+  options: ServerContext['options']
+
+  constructor (serverContext: ServerContext) {
     this.serverContext = serverContext
     this.options = serverContext.options
   }
 
-  renderTemplate (templateFn, opts) {
+  renderTemplate (templateFn: (options: Record<string, any>) => void, opts: Record<string, any>) {
     // Fix problem with HTMLPlugin's minify option (#3392)
     opts.html_attrs = opts.HTML_ATTRS
     opts.head_attrs = opts.HEAD_ATTRS
@@ -13,7 +18,7 @@ export default class BaseRenderer {
     return templateFn(opts)
   }
 
-  render () {
+  render (renderContext) {
     throw new Error('`render()` needs to be implemented')
   }
 }
diff --git a/packages/nuxt3/src/vue-renderer/renderers/modern.ts b/packages/nuxt3/src/vue-renderer/renderers/modern.ts
index 83fc24efc3..a98f0c45a9 100644
--- a/packages/nuxt3/src/vue-renderer/renderers/modern.ts
+++ b/packages/nuxt3/src/vue-renderer/renderers/modern.ts
@@ -1,8 +1,13 @@
+import ServerContext from 'nuxt/server/context'
 import { isUrl, urlJoin, safariNoModuleFix } from 'nuxt/utils'
+
 import SSRRenderer from './ssr'
 
 export default class ModernRenderer extends SSRRenderer {
-  constructor (serverContext) {
+  _assetsMapping?: Record<string, string>
+  publicPath: string
+
+  constructor (serverContext: ServerContext) {
     super(serverContext)
 
     const { build: { publicPath }, router: { base } } = this.options
@@ -17,7 +22,7 @@ export default class ModernRenderer extends SSRRenderer {
     const { clientManifest, modernManifest } = this.serverContext.resources
     const legacyAssets = clientManifest.assetsMapping
     const modernAssets = modernManifest.assetsMapping
-    const mapping = {}
+    const mapping: Record<string, string> = {}
 
     Object.keys(legacyAssets).forEach((componentHash) => {
       const modernComponentAssets = modernAssets[componentHash] || []
diff --git a/packages/nuxt3/src/vue-renderer/renderers/spa.ts b/packages/nuxt3/src/vue-renderer/renderers/spa.ts
index f557752192..88ead6bc89 100644
--- a/packages/nuxt3/src/vue-renderer/renderers/spa.ts
+++ b/packages/nuxt3/src/vue-renderer/renderers/spa.ts
@@ -3,11 +3,22 @@ import cloneDeep from 'lodash/cloneDeep'
 import VueMeta from 'vue-meta'
 import LRU from 'lru-cache'
 import devalue from '@nuxt/devalue'
+
 import { TARGETS, isModernRequest } from 'nuxt/utils'
+import ServerContext from 'nuxt/server/context'
 import BaseRenderer from './base'
 
 export default class SPARenderer extends BaseRenderer {
-  constructor (serverContext) {
+  cache: LRU<unknown, unknown>
+  vueMetaConfig: {
+    ssrAppId: string
+    keyName: string
+    attribute: string
+    ssrAttribute: string
+    tagIDKeyName: string
+  }
+
+  constructor (serverContext: ServerContext) {
     super(serverContext)
 
     this.cache = new LRU()
@@ -188,7 +199,7 @@ export default class SPARenderer extends BaseRenderer {
     }
   }
 
-  static getPreloadType (ext) {
+  static getPreloadType (ext: string) {
     if (ext === 'js') {
       return 'script'
     } else if (ext === 'css') {
diff --git a/packages/nuxt3/src/vue-renderer/renderers/ssr.ts b/packages/nuxt3/src/vue-renderer/renderers/ssr.ts
index d75a05dc88..d542294144 100644
--- a/packages/nuxt3/src/vue-renderer/renderers/ssr.ts
+++ b/packages/nuxt3/src/vue-renderer/renderers/ssr.ts
@@ -3,13 +3,15 @@ import crypto from 'crypto'
 import { format } from 'util'
 import fs from 'fs-extra'
 import consola from 'consola'
-import { TARGETS, urlJoin } from 'nuxt/utils'
 import devalue from '@nuxt/devalue'
 import { createBundleRenderer } from 'vue-bundle-renderer'
+
+import { TARGETS, urlJoin } from 'nuxt/utils'
+import ServerContext from 'nuxt/server/context'
 import BaseRenderer from './base'
 
 export default class SSRRenderer extends BaseRenderer {
-  constructor (serverContext) {
+  constructor (serverContext: ServerContext) {
     super(serverContext)
     this.createRenderer()
   }