Next.js Codebase Analysis <> create-next-app <> index.ts explained - Part 1.7

In the previous article, we looked at projectPath. In this article, you will understand the code behind the name prompt you see when you create a new nextjs project.

run() function checks if projectPath is set to choose a name for your project passed as part of command. For example, npx create-next-app my-app

But if you did not pass variable name, Commander does not set anything in action and you will be prompted to provide a name for your project.

The following code shows the prompt, I added the comments explaining what code does.

if (!projectPath) {
    // Read more about prompts here: 
    // https://www.npmjs.com/package/prompts
    const res = await prompts({
      // onPromptState is a function available at
      // https://github.com/vercel/next.js/blob/canary/packages/create-next-app/index.ts#L25
      onState: onPromptState,
      type: 'text',
      name: 'path',
      message: 'What is your project named?',
      initial: 'my-app',
      // validates ensures to follow npm package name guidelines
      // availabe here: https://www.npmjs.com/package/validate-npm-package-name
      validate: (name) => {
        const validation = validateNpmName(path.basename(path.resolve(name)))
        if (validation.valid) {
          return true
        }
        return 'Invalid project name: ' + validation.problems[0]
      },
    })

    if (typeof res.path === 'string') {
      projectPath = res.path.trim()
    }
  }

An example showing what happens when you try to name your project that does not conform to npm naming restrictions.

Conclusion:

prompts and validate-npm-package-name packages are used to take the user input for project name. Now you know how this name prompt works.

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