Building CLI Tools with inquirerer

A comprehensive guide to building interactive command-line interfaces using inquirerer, the TypeScript-first CLI library used across Constructive projects.

When to Apply

Use this skill when:

• Creating a new CLI application
• Adding interactive prompts to an existing tool
• Building project scaffolding or setup wizards
• Creating configuration builders
• Implementing any command-line interface in a Constructive project

Installation

pnpm add inquirerer

Quick Start

import { Inquirerer } from 'inquirerer';

const prompter = new Inquirerer();

const answers = await prompter.prompt({}, [
  {
    type: 'text',
    name: 'projectName',
    message: 'What is your project name?',
    required: true
  },
  {
    type: 'confirm',
    name: 'useTypeScript',
    message: 'Use TypeScript?',
    default: true
  }
]);

console.log(answers);
prompter.close();

Question Types

inquirerer supports six question types:

Text Question

Collect string input:

{
  type: 'text',
  name: 'username',
  message: 'Enter your username',
  required: true,
  pattern: '^[a-z0-9_]+$',  // Regex validation
  default: 'user'
}

Number Question

Collect numeric input:

{
  type: 'number',
  name: 'port',
  message: 'Server port?',
  default: 3000,
  validate: (port) => port > 0 && port < 65536
}

Confirm Question

Yes/no questions:

{
  type: 'confirm',
  name: 'proceed',
  message: 'Continue with installation?',
  default: true
}

List Question

Select one option (no search):

{
  type: 'list',
  name: 'license',
  message: 'Choose a license',
  options: ['MIT', 'Apache-2.0', 'GPL-3.0'],
  default: 'MIT',
  maxDisplayLines: 5
}

Autocomplete Question

Select with fuzzy search:

{
  type: 'autocomplete',
  name: 'framework',
  message: 'Choose a framework',
  options: [
    { name: 'React', value: 'react' },
    { name: 'Vue.js', value: 'vue' },
    { name: 'Angular', value: 'angular' }
  ],
  allowCustomOptions: true,
  maxDisplayLines: 8
}

Checkbox Question

Multi-select with search:

{
  type: 'checkbox',
  name: 'features',
  message: 'Select features',
  options: ['Auth', 'Database', 'API', 'Testing'],
  default: ['Auth', 'API'],
  returnFullResults: false,  // Only return selected items
  required: true
}

Question Properties

All questions support these base properties:

Validation

Pattern Validation

{
  type: 'text',
  name: 'email',
  message: 'Enter email',
  pattern: '^[^@]+@[^@]+\\.[^@]+$'
}

Custom Validation

{
  type: 'text',
  name: 'password',
  message: 'Enter password',
  validate: (input) => {
    if (input.length < 8) {
      return { success: false, reason: 'Must be at least 8 characters' };
    }
    return { success: true };
  }
}

Sanitization

{
  type: 'text',
  name: 'tags',
  message: 'Enter tags (comma-separated)',
  sanitize: (input) => input.split(',').map(t => t.trim())
}

Conditional Questions

Show questions based on previous answers:

const questions = [
  {
    type: 'confirm',
    name: 'useDatabase',
    message: 'Need a database?',
    default: false
  },
  {
    type: 'list',
    name: 'database',
    message: 'Which database?',
    options: ['PostgreSQL', 'MySQL', 'SQLite'],
    when: (answers) => answers.useDatabase === true
  }
];

Question Dependencies

Ensure questions appear in correct order:

[
  {
    type: 'checkbox',
    name: 'services',
    message: 'Select services',
    options: ['Auth', 'Storage', 'Functions']
  },
  {
    type: 'text',
    name: 'authProvider',
    message: 'Auth provider?',
    dependsOn: ['services'],
    when: (answers) => answers.services?.includes('Auth')
  }
]

Positional Arguments

Allow values without flags using _: true:

const questions = [
  { _: true, name: 'source', type: 'text', message: 'Source file' },
  { _: true, name: 'dest', type: 'text', message: 'Destination' }
];

// Users can run: mycli input.txt output.txt
// Instead of: mycli --source input.txt --dest output.txt

Aliases

Define short flags:

{
  name: 'workspace',
  type: 'confirm',
  alias: 'w',  // or ['w', 'ws'] for multiple
  message: 'Create workspace?'
}

// Users can run: mycli -w
// Instead of: mycli --workspace

Dynamic Defaults with Resolvers

Auto-populate defaults from git, npm, or custom sources:

const questions = [
  {
    type: 'text',
    name: 'author',
    message: 'Author name?',
    defaultFrom: 'git.user.name'  // Auto-fills from git config
  },
  {
    type: 'text',
    name: 'email',
    message: 'Email?',
    defaultFrom: 'git.user.email'
  },
  {
    type: 'text',
    name: 'year',
    message: 'Copyright year?',
    defaultFrom: 'date.year'
  }
];

Built-in Resolvers

Custom Resolvers

import { registerDefaultResolver } from 'inquirerer';

registerDefaultResolver('cwd.name', () => {
  return process.cwd().split('/').pop();
});

// Use in questions
{
  type: 'text',
  name: 'projectName',
  defaultFrom: 'cwd.name'
}

setFrom vs defaultFrom

• defaultFrom: Sets as default, user can override
• setFrom: Auto-sets value, skips prompt entirely

{
  type: 'text',
  name: 'createdAt',
  setFrom: 'date.iso'  // Auto-set, no prompt shown
}

CLI Class

For complete CLI applications with argument parsing:

import { CLI, CommandHandler, CLIOptions } from 'inquirerer';

const handler: CommandHandler = async (argv, prompter, options) => {
  const answers = await prompter.prompt(argv, [
    { type: 'text', name: 'name', message: 'Name?', required: true }
  ]);
  console.log('Hello,', answers.name);
};

const options: Partial<CLIOptions> = {
  version: 'myapp@1.0.0',
  minimistOpts: {
    alias: { v: 'version', h: 'help' }
  }
};

const cli = new CLI(handler, options);
await cli.run();

CLI Utilities

inquirerer provides utilities for building CLIs:

import { 
  parseArgv,           // Parse command-line arguments
  extractFirst,        // Extract subcommand
  getPackageVersion,   // Get version from package.json
  cliExitWithError     // Exit with error message
} from 'inquirerer';

const argv = parseArgv(process.argv);
const { first: command, newArgv } = extractFirst(argv);

switch (command) {
  case 'init':
    await handleInit(newArgv);
    break;
  case 'build':
    await handleBuild(newArgv);
    break;
  default:
    console.log('Unknown command');
}

UI Components

Spinner

import { createSpinner } from 'inquirerer';

const spinner = createSpinner('Loading...');
spinner.start();
await doWork();
spinner.succeed('Done!');
// Or: spinner.fail('Failed'), spinner.warn('Warning')

Progress Bar

import { createProgress } from 'inquirerer';

const progress = createProgress('Installing');
progress.start();
for (let i = 0; i < items.length; i++) {
  await processItem(items[i]);
  progress.update((i + 1) / items.length);
}
progress.complete('Installed');

Streaming Text

import { createStream } from 'inquirerer';

const stream = createStream({ showCursor: true });
stream.start();
for await (const token of llmResponse) {
  stream.append(token);
}
stream.done();

Non-Interactive Mode

For CI/CD environments:

const prompter = new Inquirerer({
  noTty: true,      // Disable interactive mode
  useDefaults: true // Use defaults without prompting
});

Complete Example

import { Inquirerer, Question, parseArgv } from 'inquirerer';

interface ProjectConfig {
  name: string;
  description: string;
  typescript: boolean;
  features: string[];
}

const argv = parseArgv(process.argv);
const prompter = new Inquirerer();

const questions: Question[] = [
  {
    _: true,
    type: 'text',
    name: 'name',
    message: 'Project name',
    required: true,
    pattern: '^[a-z0-9-]+$',
    defaultFrom: 'cwd.name'
  },
  {
    type: 'text',
    name: 'description',
    message: 'Description',
    default: 'My awesome project'
  },
  {
    type: 'confirm',
    name: 'typescript',
    alias: 'ts',
    message: 'Use TypeScript?',
    default: true
  },
  {
    type: 'checkbox',
    name: 'features',
    message: 'Select features',
    options: ['ESLint', 'Prettier', 'Jest', 'Husky'],
    default: ['ESLint', 'Prettier']
  }
];

const config = await prompter.prompt<ProjectConfig>(argv, questions);
console.log('Creating project:', config);
prompter.close();

Run interactively or with CLI args:

# Interactive
node setup.js

# With args
node setup.js my-project --ts --features ESLint,Jest

Best Practices

1. Always close the prompter when done: prompter.close()
2. Use TypeScript interfaces for type-safe answers
3. Provide defaults for better UX
4. Use defaultFrom for dynamic defaults from git/npm
5. Support non-interactive mode for CI/CD
6. Use positional arguments for common inputs
7. Add aliases for frequently used flags
8. Validate early with patterns and custom validators

References

• npm package: https://www.npmjs.com/package/inquirerer
• Related skill: inquirerer-anti-patterns for what NOT to do
• Related skill: pnpm-workspace for monorepo setup