Scaffold Tooling — TypeScript Quality Infrastructure

You are setting up (or upgrading) the quality tooling infrastructure for a TypeScript project. This skill handles ESLint, TypeScript compiler config, Prettier, and git hooks — the deterministic enforcement layer.

Instructions

1. Detect environment

Detect the package manager from lockfiles:

• •pnpm-lock.yaml → pnpm
• •yarn.lock → yarn
• •bun.lockb or bun.lock → bun
• •package-lock.json or none → npm

Check for existing config files:

• •tsconfig.json or tsconfig.base.json
• •eslint.config.mjs / eslint.config.js / .eslintrc.*
• •.prettierrc*
• •.husky/
• •package.json

If any exist, inform the user this is an upgrade and list what will be modified. Ask for confirmation before proceeding.

2. Configure tsconfig.json (Rule 3.1)

Read the template at .claude/skills/scaffold-tooling/templates/tsconfig.json.template.

Create or update tsconfig.json with the strict configuration. If a tsconfig already exists, show the user a diff of what will change and confirm.

Key flags that must be present:

• •strict: true
• •useUnknownInCatchVariables: true
• •noUncheckedIndexedAccess: true
• •exactOptionalPropertyTypes: true
• •isolatedModules: true
• •noFallthroughCasesInSwitch: true
• •noImplicitReturns: true
• •noUnusedLocals: true
• •noUnusedParameters: true

3. Configure ESLint (Rule 3.3)

Read the template at .claude/skills/scaffold-tooling/templates/eslint.config.mjs.template.

This uses ESLint 9 flat config format. The template includes:

• •@typescript-eslint/recommended-type-checked + stylistic-type-checked base
• •no-restricted-syntax: TSEnumDeclaration (Rule 3.5)
• •no-var + prefer-const (Rule 5.2)
• •@typescript-eslint/prefer-readonly (Rule 7.1)
• •@typescript-eslint/switch-exhaustiveness-check (Rule 8.3)
• •max-lines-per-function (40), max-params (4), max-depth (3), complexity (10) (Rule 8.4)
• •no-console with allow warn/error (Rule 6.3)
• •no-eval (Security)
• •import/no-cycle with maxDepth 5 (Rule 10.3)
• •import/no-dynamic-require (Rule 3.4)
• •eslint-config-prettier rules spread last

If the project uses legacy .eslintrc.* format, inform the user it should be migrated to flat config and provide migration guidance.

4. Configure Prettier

Read the template at .claude/skills/scaffold-tooling/templates/prettierrc.json.template.

Create .prettierrc.json and .prettierignore if they don't exist.

5. Configure Husky + lint-staged

Set up pre-commit hooks:

# .husky/pre-commit
<pm> run lint
<pm> run typecheck

Add lint-staged config to package.json:

{
  "lint-staged": {
    "src/**/*.{ts,tsx}": ["<pm> exec eslint --fix --max-warnings=0"],
    "*.{json,md,yml,yaml,ts,tsx,js}": ["<pm> exec prettier --write"]
  }
}

Replace <pm> with the detected package manager.

6. Add/merge package.json scripts

Ensure these scripts exist (merge, don't overwrite existing custom scripts):

{
  "scripts": {
    "typecheck": "tsc --noEmit",
    "lint": "eslint . --ext .ts,.tsx --max-warnings=0",
    "lint:fix": "eslint . --ext .ts,.tsx --fix",
    "format": "prettier . --check",
    "format:fix": "prettier . --write",
    "check": "<pm> run lint && <pm> run typecheck && <pm> run test",
    "prepare": "husky"
  }
}

7. List install commands

Tell the user to run the following commands (do NOT run them automatically):

# Core tooling
<pm> install --save-exact -D typescript @typescript-eslint/parser @typescript-eslint/eslint-plugin eslint

# Import management
<pm> install --save-exact -D eslint-plugin-import eslint-import-resolver-typescript eslint-plugin-simple-import-sort

# Prettier integration
<pm> install --save-exact -D prettier eslint-config-prettier

# Git hooks
<pm> install --save-exact -D husky lint-staged

8. Summary

List all files created or modified, all install commands needed, and any manual steps.

Important Notes

• •Never run install commands automatically — list them for the user to review
• •If upgrading, show diffs and ask for confirmation before overwriting
• •Package-manager agnostic: use the detected PM for all commands
• •ESLint 9 flat config only — do not generate legacy .eslintrc.* files
• •Templates provide the baseline; the user may need to adjust for project-specific needs (e.g., relaxing rules for test files)