Add --use-yarn flag to create-next-app (#49407)

# Add `--use-yarn` flag to `create-next-app` fixes #49405 - [x] Implement `--use-yarn` flag - [x] Update docs - [x] Add tests Co-authored-by: Tobias Koppers <tobias.koppers@googlemail.com>
vercel · May 10, 2023 · 428342d · 428342d
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diff --git a/docs/api-reference/create-next-app.md b/docs/api-reference/create-next-app.md
@@ -77,6 +77,10 @@ Options:
 
     Explicitly tell the CLI to bootstrap the app using pnpm
 
+  --use-yarn
+
+    Explicitly tell the CLI to bootstrap the app using Yarn
+
   -e, --example [name]|[github-url]
 
     An example to bootstrap the app with. You can use an example name

diff --git a/packages/create-next-app/README.md b/packages/create-next-app/README.md
@@ -49,6 +49,10 @@ Options:
 
     Explicitly tell the CLI to bootstrap the app using pnpm
 
+  --use-yarn
+
+    Explicitly tell the CLI to bootstrap the app using Yarn
+
   -e, --example [name]|[github-url]
 
     An example to bootstrap the app with. You can use an example name

diff --git a/packages/create-next-app/index.ts b/packages/create-next-app/index.ts
@@ -99,6 +99,13 @@ const program = new Commander.Command(packageJson.name)
     `
 
   Explicitly tell the CLI to bootstrap the application using pnpm
+`
+  )
+  .option(
+    '--use-yarn',
+    `
+
+  Explicitly tell the CLI to bootstrap the application using Yarn
 `
   )
   .option(
@@ -134,6 +141,8 @@ const packageManager = !!program.useNpm
   ? 'npm'
   : !!program.usePnpm
   ? 'pnpm'
+  : !!program.useYarn
+  ? 'yarn'
   : getPkgManager()
 
 async function run(): Promise<void> {

diff --git a/test/integration/create-next-app/index.test.ts b/test/integration/create-next-app/index.test.ts
@@ -536,6 +536,79 @@ describe('create next app', () => {
     })
   })
 
+  it('should use Yarn as the package manager on supplying --use-yarn', async () => {
+    await useTempDir(async (cwd) => {
+      const projectName = 'use-yarn'
+      const res = await run(
+        [
+          projectName,
+          '--js',
+          '--no-tailwind',
+          '--eslint',
+          '--use-yarn',
+          '--no-src-dir',
+          '--app',
+          `--import-alias=@/*`,
+        ],
+        {
+          cwd,
+        }
+      )
+
+      expect(res.exitCode).toBe(0)
+      projectFilesShouldExist({
+        cwd,
+        projectName,
+        files: [
+          'package.json',
+          'app/page.js',
+          '.gitignore',
+          '.eslintrc.json',
+          'yarn.lock',
+          'node_modules/next',
+        ],
+      })
+    })
+  })
+
+  it('should use Yarn as the package manager on supplying --use-yarn with example', async () => {
+    try {
+      await execa('yarn', ['--version'])
+    } catch (_) {
+      // install yarn if not available
+      await execa('npm', ['i', '-g', 'yarn'])
+    }
+
+    await useTempDir(async (cwd) => {
+      const projectName = 'use-yarn'
+      const res = await run(
+        [
+          projectName,
+          '--js',
+          '--no-tailwind',
+          '--eslint',
+          '--use-yarn',
+          '--example',
+          `${exampleRepo}/${examplePath}`,
+        ],
+        { cwd }
+      )
+
+      expect(res.exitCode).toBe(0)
+      projectFilesShouldExist({
+        cwd,
+        projectName,
+        files: [
+          'package.json',
+          'pages/index.tsx',
+          '.gitignore',
+          'yarn.lock',
+          'node_modules/next',
+        ],
+      })
+    })
+  })
+
   it('should use pnpm as the package manager on supplying --use-pnpm', async () => {
     await useTempDir(async (cwd) => {
       const projectName = 'use-pnpm'