kotlin-development
Kotlin development guidelines with best practices for clean code, naming conventions, function design, and data handling
What this skill does
# Kotlin Development Best Practices ## General Principles - Use English for all code and documentation - Always declare the type of each variable and function - Avoid the `any` type; create necessary types instead - No blank lines within function bodies ## Naming Conventions ### Case Standards - **PascalCase**: Classes, interfaces, enums - **camelCase**: Variables, functions, methods, parameters - **UPPERCASE**: Environment variables, constants - **underscores_case**: Files and directories ### Naming Guidelines - Start each function with a verb (get, set, create, update, delete, etc.) - Use complete words over abbreviations - Allowed abbreviations: API, URL, i/j for loops, err, ctx, req/res/next - Avoid magic numbers; define constants instead - Boolean variables use prefixes: `isLoading`, `hasError`, `canDelete` ## Function Design ### Size and Responsibility - Keep functions under 20 instructions - Each function should have a single responsibility - Extract logic into utility functions when complexity increases ### Naming Functions - Use verb-based naming that describes the action - Prefix boolean-returning functions with `is`, `has`, or `can` - Prefix void functions with action verbs like `execute`, `save`, `send` ### Reducing Nesting - Use early returns to handle edge cases first - Extract nested logic into separate functions - Employ higher-order functions (map, filter, reduce) to minimize loops - Prefer arrow functions for simple operations; use named functions otherwise ### Parameters - Use default parameters instead of null checks - When functions have multiple parameters, consolidate them into objects (RO-RO pattern) - Keep parameter lists short (max 3-4 parameters) ## Data Handling ### Data Classes - Use data classes for data structures - Encapsulate primitive types in composite types when they represent domain concepts - Validate data internally within data classes ### Immutability - Prefer immutability for data - Use `val` for variables that don't change - Use immutable collections when possible - Create new instances instead of mutating existing ones ## Classes and Objects ### Size Guidelines - Keep classes under 200 instructions - Limit to fewer than 10 public methods - Limit to fewer than 10 properties ### Design Principles - Follow SOLID principles - Favor composition over inheritance - Use interfaces for abstraction - Keep classes focused on a single responsibility ## Exception Handling ### When to Use Exceptions - Reserve exceptions for truly unexpected errors - Don't use exceptions for control flow - Catch exceptions only to: - Fix an anticipated issue - Add context before re-throwing ### Best Practices - Create custom exception types for domain-specific errors - Include meaningful error messages - Log exceptions at appropriate levels ## Testing ### Unit Tests - Follow Arrange-Act-Assert convention - Write unit tests for all public functions - Use test doubles (mocks, stubs, fakes) for dependencies - Name tests descriptively to document behavior ### Acceptance Tests - Follow Given-When-Then convention - Test user-facing behavior and scenarios - Keep tests independent and repeatable ## Code Organization - Group related functionality together - Keep files focused and cohesive - Use packages/modules to organize code by feature or layer - Maintain consistent file structure across the project
Related in Design
contribute
IncludedLocal-only OSS contribution command center. Auto-refreshes the user's in-flight PR and issue state on invoke so conversations start with full context — no need to brief Claude on what's in flight. Helps the user find issues to contribute to on GitHub, builds per-repo dossiers of what each upstream expects (CLA, DCO, branch convention, AI policy, draft-first, review bots, issue templates), runs deterministic gates before any external action so AI-assisted contributions don't reach maintainers as slop. State is markdown-only: candidate files at ~/.contribute-system/candidates/, repo dossiers at ~/.contribute-system/research/, append-only event log at ~/.contribute-system/log.jsonl. No database, no cloud calls. Use when the user asks about their PRs / issues / contributions, wants to find new work to take on, claim an issue, build/refresh a repo's dossier, or draft a Design Issue or PR. Trigger with "/contribute", "what's my PR status", "find a contribution", "claim issue X", "draft a Design Issue for Y", "refresh dossier for Z".
architectural-analysis
IncludedUser-triggered deep architectural analysis of a codebase or scoped subtree across eight modes — information architecture, data flow, integration points, UI surfaces, interaction patterns, data model, control flow, and failure modes. This skill should be used when the user asks to "diagram this codebase," "map the architecture," "show the data flow," "give me an ERD," "trace control flow," "find the integration points," "verify the layout pattern," "audit the UX architecture," or any similar request whose primary deliverable is mermaid diagrams plus cited reports under docs/architecture/. Dispatches haiku/sonnet sub-agents in parallel for per-mode exploration, then verifies every citation mechanically before any node lands in a diagram. Not for one-off prose explanations of code (use code-explanation) or for high-level system design from scratch (use system-design).
mcp
IncludedModel Context Protocol (MCP) server development and tool management. Languages: Python, TypeScript. Capabilities: build MCP servers, integrate external APIs, discover/execute MCP tools, manage multi-server configs, design agent-centric tools. Actions: create, build, integrate, discover, execute, configure MCP servers/tools. Keywords: MCP, Model Context Protocol, MCP server, MCP tool, stdio transport, SSE transport, tool discovery, resource provider, prompt template, external API integration, Gemini CLI MCP, Claude MCP, agent tools, tool execution, server config. Use when: building MCP servers, integrating external APIs as MCP tools, discovering available MCP tools, executing MCP capabilities, configuring multi-server setups, designing tools for AI agents.
react-native-skia
IncludedDesign, build, debug, and optimise high-polish animated graphics in React Native or Expo using @shopify/react-native-skia, Reanimated, and Gesture Handler. Use when the user wants canvas-driven UI, shaders, paths, rich text, image filters, sprite fields, Skottie, video frames, snapshots, web CanvasKit setup, or performance tuning for custom motion-heavy elements such as loaders, hero art, cards, charts, progress indicators, particle systems, or gesture-driven surfaces. Also use when the user asks for fluid, glow, glass, blob, parallax, 60fps/120fps, or GPU-friendly animated effects in React Native, even if they do not explicitly say "Skia". Do not use for ordinary form/layout work with standard views.
plaid
IncludedProduct Led AI Development — guides founders from idea to launched product. Six capabilities: Idea (discover a product idea), Validate (pressure-test the idea against fatal flaws, problem reality, competition, and 2-week MVP feasibility), Plan (vision intake + document generation), Design (translate image references into a design.md spec), Launch (go-to-market strategy), and Build (roadmap execution). Use when someone says "PLAID", "plaid idea", "help me find an idea", "product idea", "idea from my business", "idea from my expertise", "plaid validate", "validate my idea", "pressure-test", "is this idea good", "find fatal flaws", "validate the problem", "plan a product", "define my vision", "generate a PRD", "product strategy", "plaid design", "design from image", "translate image to design", "create design.md", "extract design tokens", "plaid launch", "go-to-market", "launch plan", "GTM strategy", "launch playbook", "plaid build", "build the app", "start building", or "execute the roadmap".
nextjs-framer-motion-animations
IncludedAdds production-safe Motion for React or Framer Motion animations to Next.js apps, including reveal, hover and tap micro-interactions, whileInView, stagger, AnimatePresence, layout and layoutId transitions, reorder, scroll-linked UI, and lightweight route-content transitions. Use when the user asks to add, refactor, or debug Motion or Framer Motion in App Router or Pages Router codebases, especially around server/client boundaries, reduced motion, LazyMotion, bundle size, hydration, or route transitions. Avoid for GSAP-style timelines, WebGL or 3D scenes, heavy scroll storytelling, or CSS-only effects unless Motion is explicitly requested.