[backport] [CNA] use linter preference (#83194)

[devjiwonchoi]

backports #83194

[ijjk]

Tests Passed

[vercel]

Suggested change

	],
	] ?? 0,

The code could fail if the user's linter preference contains an unexpected value, causing undefined to be passed as the initial prompt selection.

View Details

Analysis

Undefined initial value passed to prompts when linter preference is invalid

What fails: The linterIndexMap lookup in packages/create-next-app/index.ts:321-324 returns undefined when getPrefOrDefault('linter') returns a value not in the map ('eslint', 'biome', 'none'), causing the prompts library to receive initial: undefined.

How to trigger:

1. Create or modify the create-next-app config with an invalid linter preference:

# Edit ~/.config/create-next-app/config.json to contain:
{"preferences": {"linter": "invalid-value"}}

2. Run create-next-app without CLI linter flags to trigger the interactive prompt

Result: The prompts library receives initial: undefined instead of a valid array index, leading to unpredictable default selection behavior.

Expected: Should default to a valid index (0 = ESLint) when the preference value is not recognized, ensuring consistent user experience.

Fix applied: Added nullish coalescing operator ?? 0 to provide fallback to first option (ESLint) when lookup returns undefined.

[devjiwonchoi]

We will get at least a default value so wouldn't be undefined