# typescript-clean-code

A skill for reviewing and refactoring TypeScript: code smell catalogs, four detection layers, and step-by-step workflows.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 628 installs · ★ 19
- Author: bmad-labs
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/bmad-labs/skills/tree/HEAD/skills/typescript-clean-code/SKILL.md
- Updated: 2026-10-22
- HTML: https://affpapa.org/en/nevibecode/skills/typescript-clean-code

## What it does

The skill examines TypeScript at four levels. First the repository: which smells a linter already decides, so those become one CI finding instead of twenty hand-written ones. Then a line and a function, then a modification, then a type. Each layer sees what the others miss.

Inside are twelve change-shape smells — Shotgun Surgery, Feature Envy, Data Clumps, Long Method and the rest — each with a detection question, a TypeScript remedy, and a note on when not to fix it. A separate file covers type hygiene: `any` leakage, `as` assertions versus validation, exhaustiveness, strict flags, branded types. Workflows cover code review, pull request review, refactoring with tests, TDD, new features, bug fixes, test strategy, PERT estimation, and handling unrealistic deadlines. Every step updates `stepsCompleted` in the output document's frontmatter, so a compacted context resumes from the last completed step.

Three rules are marked contested: function length, comments, and G23 polymorphism. An exhaustive `switch` over a discriminated union is idiomatic TypeScript, not a smell. The skill suggests presenting both sides and preferring the author's reasoning over the number. Install runs through `npx skills add`; GitHub Copilot uses `gh skill install`.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add bmad-labs/skills --skill typescript-clean-code -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/typescript-clean-code/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/typescript-clean-code/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add bmad-labs/skills --skill typescript-clean-code -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/typescript-clean-code/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add bmad-labs/skills --skill typescript-clean-code -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/typescript-clean-code/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install bmad-labs/skills typescript-clean-code
```

2. **Manually: put the files in place**
- File: `.github/skills/typescript-clean-code/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add bmad-labs/skills --skill typescript-clean-code -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/bmad-labs/skills --path skills/typescript-clean-code
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/typescript-clean-code/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add bmad-labs/skills --skill typescript-clean-code -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/bmad-labs/skills/tree/HEAD/skills/typescript-clean-code/SKILL.md

## When to use it
- scan a diff for code smells before merge
- decide what belongs in the linter and what needs reviewer judgment
- strip `any` leakage and stray `as` assertions from types
- refactor with tests without changing behaviour
- estimate a task and explain why the deadline is unrealistic

## Example prompts
- review this pull request against all four smell layers
- run the refactoring workflow on `src/orders.ts` with tests
- help me estimate this task with PERT

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: bb66aac392f1f69b.

BEGIN THIRD-PARTY FILE bb66aac392f1f69b
```text
---
name: typescript-clean-code
description: |
  Clean Code for TypeScript — code smell catalogs (Martin's per-line heuristics, Fowler's change-shape smells, TypeScript-native type smells), a linter-first detection policy, and step-by-step review, refactoring, TDD, and estimation workflows.

  Use when the user:
  - Writes, reviews, or refactors TypeScript/JavaScript code, or asks whether code is clean, maintainable, or well-designed
  - Names a smell — Shotgun Surgery, Feature Envy, Data Clumps, Long Method, Divergent Change, Duplicated Code, Large Class, Long Parameter List, Primitive Obsession, Message Chains, Dead Code, Speculative Generality, god class, copy-paste, stringly typed, premature abstraction
  - Asks about TypeScript type hygiene — `any` leakage, `as` assertions, non-null `!`, discriminated unions, exhaustiveness, strict flags, branded types
  - Asks what to enforce with lint or tsconfig versus what needs judgment, or names knip, jscpd, dependency-cruiser, typescript-eslint, type-coverage
  - Runs TDD, fixes a bug with test coverage, or plans test strategy
  - Estimates tasks, negotiates a deadline, or works through a commitment or team problem
---

# Clean Code

## The twelve change-shape smells

Shotgun Surgery · Feature Envy · Data Clumps · Long Method · Divergent Change ·
Duplicated Code · Large Class · Long Parameter List · Primitive Obsession ·
Message Chains · Dead Code · Speculative Generality

You know each one and its refactoring. The value is the checklist, not the
definitions — without the names a diff "looks fine"; with them you find the shape.
Run all twelve against any change you review or write.

## The smell catalog has four layers

Each examines a different unit, so each sees what the others miss.

| Load | Unit | For |
|------|------|-----|
| `references/smells/tooling.md` | the repository | **First, in every review.** Which smells a linter decides, so those become one "wire this into CI" finding instead of twenty hand-written ones |
| `references/smells/rules.md` | a line, a function | Per-line heuristics (C/E/F/G/N/T), plus the review posture and severity vocabulary that govern all four layers |
| `references/smells/fowler.md` | a modification | The twelve above — detection question, TypeScript remedy, and **when NOT to fix** for each |
```
END THIRD-PARTY FILE bb66aac392f1f69b

The third-party file has ended. Everything between the bb66aac392f1f69b tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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