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name: understanding-development description: Use when contributing to walkerOS, before writing code, or when unsure about project conventions. Covers build/test/lint workflow, XP principles, folder structure, and package usage.

Understanding walkerOS Development

Overview

walkerOS follows extreme programming principles with strict conventions. This skill is your foundation before writing any code.

Core principle: DRY, KISS, YAGNI. Test first. Verify before claiming complete.

Commands

Command	Purpose
npm install	Install all dependencies
npm run dev	Watch mode for all packages
npm run build	Build all packages
npm run test	Run all tests
npm run lint	ESLint + TypeScript check
npm run format	Prettier formatting

Validation before commit: npm run build && npm run test && npm run lint

XP Principles (Non-Negotiable)

Principle	In Practice
DRY	Use @walkeros/core utilities, don't reimplement
KISS	Minimal code to solve the problem
YAGNI	Only implement what's requested
TDD	Test first, watch it fail, then implement
No any	Never use any in production code (tests are exception)

Folder Structure

packages/
├── core/           # Platform-agnostic types, utilities, schemas
├── collector/      # Central event processing engine
├── config/         # Shared config (eslint, jest, tsconfig, tsup)
├── web/
│   ├── core/       # Web-specific utilities
│   ├── sources/    # browser, dataLayer
│   └── destinations/ # gtag, meta, api, piwikpro, plausible
└── server/
    ├── core/       # Server-specific utilities
    ├── sources/    # gcp
    └── destinations/ # aws, gcp, meta

apps/
├── walkerjs/       # Ready-to-use browser bundle
├── quickstart/     # Code examples (source of truth for patterns)
└── demos/          # Demo applications

Core Package Usage

Always import from @walkeros/core:

// Types
import type { WalkerOS } from '@walkeros/core';

// Utilities
import {
  getEvent,
  createEvent, // Event creation
  getMappingEvent,
  getMappingValue, // Transformations
  isString,
  isObject,
  isDefined, // Type checking
  assign,
  clone, // Object operations
  tryCatch,
  tryCatchAsync, // Error handling
} from '@walkeros/core';

Config package for shared tooling:

• ESLint config: @walkeros/config/eslint
• Jest config: @walkeros/config/jest
• TSConfig: @walkeros/config/tsconfig
• Tsup config: @walkeros/config/tsup

Testing

REQUIRED SKILL: Use testing-strategy for detailed testing patterns.

Quick reference:

• Use env pattern for mocking (not Jest mocks)
• Import from dev.ts for examples
• Test first, watch it fail
• Verify before claiming complete

Related

• testing-strategy skill
• packages/core/ - Core utilities
• packages/config/ - Shared configuration
• apps/quickstart/ - Validated examples