feat(create-next-app): add --ts, --typescript support

.eslintignore

@@ -17,6 +17,7 @@ packages/next-codemod/transforms/__tests__/**/*
 packages/next-codemod/**/*.js
 packages/next-codemod/**/*.d.ts
 packages/next-env/**/*.d.ts
+packages/create-next-app/templates/**
 test/integration/async-modules/**
 test/integration/eslint/**
 test-timings.json

docs/getting-started.md

@@ -27,6 +27,14 @@ npx create-next-app
 yarn create next-app
 ```
 
+If you want to start with a TypeScript project you can use the `--typescript` flag:
+
+```bash
+npx create-next-app --typescript
+# or
+yarn create next-app --typescript
+```
+
 After the installation is complete, follow the instructions to start the development server. Try editing `pages/index.js` and see the result on your browser.
 
 For more information on how to use `create-next-app`, you can review the [`create-next-app` documentation](/docs/api-reference/create-next-app.md)

packages/create-next-app/README.md

@@ -16,6 +16,7 @@ npx create-next-app blog-app
 
 `create-next-app` comes with the following options:
 
+- **--ts, --typescript** - Initialize as a TypeScript project.
 - **-e, --example [name]|[github-url]** - An example to bootstrap the app with. You can use an example name from the [Next.js repo](https://github.com/vercel/next.js/tree/master/examples) or a GitHub URL. The URL can use any branch and/or subdirectory.
 - **--example-path <path-to-example>** - In a rare case, your GitHub URL might contain a branch name with a slash (e.g. bug/fix-1) and the path to the example (e.g. foo/bar). In this case, you must specify the path to the example separately: `--example-path foo/bar`
 - **--use-npm** - Explicitly tell the CLI to bootstrap the app using npm. Yarn will be used by default if it's installed

packages/create-next-app/create-app.ts

@@ -28,13 +28,16 @@ export async function createApp({
   useNpm,
   example,
   examplePath,
+  typescript,
 }: {
   appPath: string
   useNpm: boolean
   example?: string
   examplePath?: string
+  typescript?: boolean
 }): Promise<void> {
   let repoInfo: RepoInfo | undefined
+  const template = typescript ? 'typescript' : 'default'
 
   if (example) {
     let repoUrl: URL | undefined
@@ -124,6 +127,9 @@ export async function createApp({
   process.chdir(root)
 
   if (example) {
+    /**
+     * If an example repository is provided, clone it.
+     */
     try {
       if (repoInfo) {
         const repoInfo2 = repoInfo
@@ -154,7 +160,7 @@ export async function createApp({
     const ignorePath = path.join(root, '.gitignore')
     if (!fs.existsSync(ignorePath)) {
       fs.copyFileSync(
-        path.join(__dirname, 'templates', 'default', 'gitignore'),
+        path.join(__dirname, 'templates', template, 'gitignore'),
         ignorePath
       )
     }
@@ -165,30 +171,83 @@ export async function createApp({
     await install(root, null, { useYarn, isOnline })
     console.log()
   } else {
+    /**
+     * Otherwise, if an example repository is not provided for cloning, proceed
+     * by installing from a template.
+     */
+    console.log(chalk.bold(`Using ${displayedCommand}.`))
+    /**
+     * Create a package.json for the new project.
+     */
     const packageJson = {
       name: appName,
       version: '0.1.0',
       private: true,
-      scripts: { dev: 'next dev', build: 'next build', start: 'next start' },
+      scripts: {
+        dev: 'next dev',
+        build: 'next build',
+        start: 'next start',
+      },
     }
+    /**
+     * Write it to disk.
+     */
     fs.writeFileSync(
       path.join(root, 'package.json'),
       JSON.stringify(packageJson, null, 2) + os.EOL
     )
+    /**
+     * These flags will be passed to `install()`.
+     */
+    const installFlags = { useYarn, isOnline }
+    /**
+     * Default dependencies.
+     */
+    const dependencies = ['react', 'react-dom', 'next']
+    /**
+     * Default devDependencies.
+     */
+    const devDependencies = []
+    /**
+     * TypeScript projects will have type definitions and other devDependencies.
+     */
+    if (typescript) {
+      devDependencies.push('typescript', '@types/react', '@types/next')
+    }
+    /**
+     * Install package.json dependencies if they exist.
+     */
+    if (dependencies.length) {
+      console.log()
+      console.log('Installing dependencies:')
+      for (const dependency of dependencies) {
+        console.log(`- ${chalk.cyan(dependency)}`)
+      }
+      console.log()
 
-    console.log(
-      `Installing ${chalk.cyan('react')}, ${chalk.cyan(
-        'react-dom'
-      )}, and ${chalk.cyan('next')} using ${displayedCommand}...`
-    )
-    console.log()
+      await install(root, dependencies, installFlags)
+    }
+    /**
+     * Install package.json devDependencies if they exist.
+     */
+    if (devDependencies.length) {
+      console.log()
+      console.log('Installing devDependencies:')
+      for (const devDependency of devDependencies) {
+        console.log(`- ${chalk.cyan(devDependency)}`)
+      }
+      console.log()
 
-    await install(root, ['react', 'react-dom', 'next'], { useYarn, isOnline })
+      const devInstallFlags = { devDependencies: true, ...installFlags }
+      await install(root, devDependencies, devInstallFlags)
+    }
     console.log()
-
+    /**
+     * Copy the template files to the target directory.
+     */
     await cpy('**', root, {
       parents: true,
-      cwd: path.join(__dirname, 'templates', 'default'),
+      cwd: path.join(__dirname, 'templates', template),
       rename: (name) => {
         switch (name) {
           case 'gitignore': {

packages/create-next-app/helpers/install.ts

@@ -2,41 +2,98 @@
 import chalk from 'chalk'
 import spawn from 'cross-spawn'
 
+interface InstallArgs {
+  /**
+   * Indicate whether to install packages using Yarn.
+   */
+  useYarn: boolean
+  /**
+   * Indicate whether there is an active Internet connection.
+   */
+  isOnline: boolean
+  /**
+   * Indicate whether the given dependencies are devDependencies.
+   */
+  devDependencies?: boolean
+}
+
+/**
+ * Spawn a package manager installation with either Yarn or NPM.
+ *
+ * @returns A Promise that resolves once the installation is finished.
+ */
 export function install(
   root: string,
   dependencies: string[] | null,
-  { useYarn, isOnline }: { useYarn: boolean; isOnline: boolean }
+  { useYarn, isOnline, devDependencies }: InstallArgs
 ): Promise<void> {
+  /**
+   * NPM-specific command-line flags.
+   */
+  const npmFlags: string[] = ['--logLevel', 'error']
+  /**
+   * Yarn-specific command-line flags.
+   */
+  const yarnFlags: string[] = []
+  /**
+   * Return a Promise that resolves once the installation is finished.
+   */
   return new Promise((resolve, reject) => {
-    let command: string
     let args: string[]
-    if (useYarn) {
-      command = 'yarnpkg'
-      args = dependencies ? ['add', '--exact'] : ['install']
-      if (!isOnline) {
-        args.push('--offline')
-      }
-      if (dependencies) {
+    let command: string = useYarn ? 'yarnpkg' : 'npm'
+
+    if (dependencies && dependencies.length) {
+      /**
+       * If there are dependencies, run a variation of `{displayCommand} add`.
+       */
+      if (useYarn) {
+        /**
+         * Call `yarn add --exact (--offline)? (-D)? ...`.
+         */
+        args = ['add', '--exact']
+        if (!isOnline) args.push('--offline')
+        args.push('--cwd', root)
+        if (devDependencies) args.push('--dev')
+        args.push(...dependencies)
+      } else {
+        /**
+         * Call `npm install [--save|--save-dev] ...`.
+         */
+        args = ['install', '--save-exact']
+        args.push(devDependencies ? '--save-dev' : '--save')
         args.push(...dependencies)
       }
-      args.push('--cwd', root)
-
-      if (!isOnline) {
-        console.log(chalk.yellow('You appear to be offline.'))
-        console.log(chalk.yellow('Falling back to the local Yarn cache.'))
-        console.log()
+    } else {
+      /**
+       * If there are no dependencies, run a variation of `{displayCommand}
+       * install`.
+       */
+      args = ['install']
+      if (useYarn) {
+        if (!isOnline) {
+          console.log(chalk.yellow('You appear to be offline.'))
+          console.log(chalk.yellow('Falling back to the local Yarn cache.'))
+          console.log()
+          args.push('--offline')
+        }
+      } else {
+        if (!isOnline) {
+          console.log(chalk.yellow('You appear to be offline.'))
+          console.log()
+        }
       }
+    }
+    /**
+     * Add any package manager-specific flags.
+     */
+    if (useYarn) {
+      args.push(...yarnFlags)
     } else {
-      command = 'npm'
-      args = ([
-        'install',
-        dependencies && '--save',
-        dependencies && '--save-exact',
-        '--loglevel',
-        'error',
-      ].filter(Boolean) as string[]).concat(dependencies || [])
+      args.push(...npmFlags)
     }
-
+    /**
+     * Spawn the installation process.
+     */
     const child = spawn(command, args, {
       stdio: 'inherit',
       env: { ...process.env, ADBLOCK: '1', DISABLE_OPENCOLLECTIVE: '1' },

packages/create-next-app/index.ts

@@ -19,7 +19,20 @@ const program = new Commander.Command(packageJson.name)
   .action((name) => {
     projectPath = name
   })
-  .option('--use-npm', 'Explicitly tell the CLI to bootstrap the app using npm')
+  .option(
+    '--ts, --typescript',
+    `
+
+  Initialize as a TypeScript project.
+`
+  )
+  .option(
+    '--use-npm',
+    `
+
+  Explicitly tell the CLI to bootstrap the app using npm
+`
+  )
   .option(
     '-e, --example [name]|[github-url]',
     `
@@ -113,6 +126,7 @@ async function run(): Promise<void> {
       useNpm: !!program.useNpm,
       example: example && example !== 'default' ? example : undefined,
       examplePath: program.examplePath,
+      typescript: program.typescript,
     })
   } catch (reason) {
     if (!(reason instanceof DownloadError)) {
@@ -131,7 +145,11 @@ async function run(): Promise<void> {
       throw reason
     }
 
-    await createApp({ appPath: resolvedProjectPath, useNpm: !!program.useNpm })
+    await createApp({
+      appPath: resolvedProjectPath,
+      useNpm: !!program.useNpm,
+      typescript: program.typescript,
+    })
   }
 }
 

packages/create-next-app/templates/typescript/README-template.md

@@ -0,0 +1,34 @@
+This is a [Next.js](https://nextjs.org/) project bootstrapped with [`create-next-app`](https://github.com/vercel/next.js/tree/canary/packages/create-next-app).
+
+## Getting Started
+
+First, run the development server:
+
+```bash
+npm run dev
+# or
+yarn dev
+```
+
+Open [http://localhost:3000](http://localhost:3000) with your browser to see the result.
+
+You can start editing the page by modifying `pages/index.js`. The page auto-updates as you edit the file.
+
+[API routes](https://nextjs.org/docs/api-routes/introduction) can be accessed on [http://localhost:3000/api/hello](http://localhost:3000/api/hello). This endpoint can be edited in `pages/api/hello.js`.
+
+The `pages/api` directory is mapped to `/api/*`. Files in this directory are treated as [API routes](https://nextjs.org/docs/api-routes/introduction) instead of React pages.
+
+## Learn More
+
+To learn more about Next.js, take a look at the following resources:
+
+- [Next.js Documentation](https://nextjs.org/docs) - learn about Next.js features and API.
+- [Learn Next.js](https://nextjs.org/learn) - an interactive Next.js tutorial.
+
+You can check out [the Next.js GitHub repository](https://github.com/vercel/next.js/) - your feedback and contributions are welcome!
+
+## Deploy on Vercel
+
+The easiest way to deploy your Next.js app is to use the [Vercel Platform](https://vercel.com/new?utm_medium=default-template&filter=next.js&utm_source=create-next-app&utm_campaign=create-next-app-readme) from the creators of Next.js.
+
+Check out our [Next.js deployment documentation](https://nextjs.org/docs/deployment) for more details.

packages/create-next-app/templates/typescript/gitignore

@@ -0,0 +1,34 @@
+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.js
+
+# testing
+/coverage
+
+# next.js
+/.next/
+/out/
+
+# production
+/build
+
+# misc
+.DS_Store
+*.pem
+
+# debug
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# local env files
+.env.local
+.env.development.local
+.env.test.local
+.env.production.local
+
+# vercel
+.vercel

packages/create-next-app/templates/typescript/next-env.d.ts

@@ -0,0 +1,2 @@
+/// <reference types="next" />
+/// <reference types="next/types/global" />