Fix default value handling for CNA in CI (vercel#42596)

Fixes: vercel#42592

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have a helpful link attached, see `contributing.md`

Author: ijjk

packages/create-next-app/index.ts

@@ -157,14 +157,13 @@ async function run(): Promise<void> {
    * to use TS or JS.
    */
   if (!example) {
-    if (ciInfo.isCI) {
-      // default to JavaScript in CI as we can't prompt to
-      // prevent breaking setup flows
-      program.javascript = true
-      program.typescript = false
-      program.eslint = true
-    } else {
-      if (!program.typescript && !program.javascript) {
+    if (!program.typescript && !program.javascript) {
+      if (ciInfo.isCI) {
+        // default to JavaScript in CI as we can't prompt to
+        // prevent breaking setup flows
+        program.typescript = false
+        program.javascript = true
+      } else {
         const styledTypeScript = chalk.hex('#007acc')('TypeScript')
         const { typescript } = await prompts(
           {
@@ -186,18 +185,21 @@ async function run(): Promise<void> {
             },
           }
         )
-
         /**
          * Depending on the prompt response, set the appropriate program flags.
          */
         program.typescript = Boolean(typescript)
         program.javascript = !Boolean(typescript)
       }
+    }
 
-      if (
-        !process.argv.includes('--eslint') &&
-        !process.argv.includes('--no-eslint')
-      ) {
+    if (
+      !process.argv.includes('--eslint') &&
+      !process.argv.includes('--no-eslint')
+    ) {
+      if (ciInfo.isCI) {
+        program.eslint = true
+      } else {
         const styledEslint = chalk.hex('#007acc')('ESLint')
         const { eslint } = await prompts({
           type: 'toggle',

test/integration/create-next-app/lib/utils.ts

@@ -23,7 +23,6 @@ export const createNextApp = (args: string[], options?: SpawnOptions) => {
     ...options,
     env: {
       ...process.env,
-      ...options.env,
       // unset CI env as this skips the auto-install behavior
       // being tested
       CI: '',
@@ -32,6 +31,7 @@ export const createNextApp = (args: string[], options?: SpawnOptions) => {
       CONTINUOUS_INTEGRATION: '',
       RUN_ID: '',
       BUILD_NUMBER: '',
+      ...options.env,
     },
   })
 }

test/integration/create-next-app/templates.test.ts

@@ -67,6 +67,24 @@ describe('create-next-app templates', () => {
     })
   })
 
+  it('should create TS projects with --ts, --typescript with CI=1', async () => {
+    await useTempDir(async (cwd) => {
+      const projectName = 'typescript-test'
+      const childProcess = createNextApp([projectName, '--ts', '--eslint'], {
+        cwd,
+        env: {
+          ...process.env,
+          CI: '1',
+          GITHUB_ACTIONS: '1',
+        },
+      })
+      const exitCode = await spawnExitPromise(childProcess)
+
+      expect(exitCode).toBe(0)
+      shouldBeTypescriptProject({ cwd, projectName, template: 'default' })
+    })
+  })
+
   it('should create JS projects with --js, --javascript', async () => {
     await useTempDir(async (cwd) => {
       const projectName = 'javascript-test'