# Kotlin Coding Practices

> Use when authoring or reviewing Kotlin, 4-space layout, PascalCase/camelCase naming, package-aligned files, class member order, val immutability, default parameters, expression if/when, and explicit library API.

- Skill: `ryan-brosas/kotlin-coding-practices` (Agent Skill)
- Install (CLI): `npx skillmds@latest add ryan-brosas/kotlin-coding-practices`
- Raw SKILL.md: https://api.skillmd.com/api/skills/ryan-brosas/kotlin-coding-practices/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Integrations & APIs
- Author: ryan-brosas (https://skillmd.com/u/ryan-brosas)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/ryan-brosas/kotlin-coding-practices

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# Kotlin Coding Practices

Application skill for Kotlin style learning (from the archived `awesome-guidelines` style capsules). For Android/Compose/KMP stack patterns, load stack capsules in `skills/*-foundation`.

## Core Principle

Kotlin readability is **official formatter mechanics plus immutability-first idioms**, explicit imports, semantic class layout, stable library surfaces.

## When to Use / NOT

- Kotlin JVM/KMP/application/library source, ktlint/detekt CI.
- Reviewing naming, formatting, class organization, public API.

**NOT when:**

- Non-Kotlin code.
- Generated code, validate generators, not hand-edits.
- Compose/Android-only rules, use Android style guide / foundation when stack is Android.

## Workflow

1. **Format & layout**, 4-space, braces, modifiers, trailing commas (`kotlin-style-formatting-layout.md`).
2. **Naming & files**, packages, files, constants, backing props (`kotlin-style-naming-files.md`).
3. **Organization**, directories, class layout, overloads (`kotlin-style-organization-classes.md`).
4. **Idioms & API**, val, defaults, expression control flow, library KDoc (`kotlin-style-idioms-api.md`).
5. **Verify**, ktlint/detekt + `./gradlew check` (or project equivalent) on changed modules.

## Red Flags

- Wildcard imports
- Tabs or inconsistent indent
- `var` when never reassigned
- Mutable collection types in public API parameters
- Overloads instead of default parameters
- `Util.kt` / meaningless file names
- Binary `when` instead of `if`
- Public API without return types (libraries)

## Verification

- ktlint/detekt on changed files
- Compile + tests for touched modules
- Capsule checklist on public API review


## References

- `awesome-guidelines/references/kotlin-style-learning-note.md`
- `awesome-guidelines/references/kotlin-style-formatting-layout.md`
- `awesome-guidelines/references/kotlin-style-naming-files.md`
- `awesome-guidelines/references/kotlin-style-organization-classes.md`
- `awesome-guidelines/references/kotlin-style-idioms-api.md`