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ln-741-linter-configurator

Type: L3 Worker Category: 7XX Project Bootstrap Parent: ln-740-quality-setup

Configures code linting, formatting, and type checking tools for TypeScript, Python, and .NET projects.

Purpose & Scope

Does:

• Detects which linter stack to configure based on project type
• Checks for existing linter configurations
• Generates appropriate config files from templates
• Installs required dependencies (always latest versions, no pinning)
• Generates unified lint script (scripts/lint.sh)
• Verifies all linters run without errors

Does NOT:

• Configure pre-commit hooks (ln-742 does this)
• Set up test infrastructure (ln-743 does this)
• Modify source code

Supported Stacks

Phase 1: Check Existing Configuration

Before generating configs, check what already exists.

Files to Check:

Decision Logic:

1. If config exists and is complete: SKIP (inform user)
2. If config exists but incomplete: ASK user to merge or replace
3. If no config exists: CREATE from template

Phase 2: Generate Configuration

Use templates from references/ folder. Customize placeholders based on project.

TypeScript:

1. Copy eslint_template.ts to project root as eslint.config.ts
2. Copy prettier_template.json as .prettierrc
3. Add scripts to package.json:
   • "lint": "eslint ."
   • "lint:fix": "eslint . --fix"
   • "format": "prettier --write ."
   • "format:check": "prettier --check ."
   • "typecheck": "tsc --noEmit"
   • "lint:all": "npm run typecheck && npm run lint && npm run format:check"
4. For React projects: uncomment React sections in template

.NET:

1. Copy editorconfig_template.ini as .editorconfig
2. Copy directory_build_props_template.xml as Directory.Build.props
3. Ensure analyzers are included (SDK 5+ includes them by default)

Python:

1. Copy ruff_template.toml as ruff.toml
   • OR merge into existing pyproject.toml under [tool.ruff]
2. Copy mypy_template.toml as mypy.toml
   • OR merge into existing pyproject.toml under [tool.mypy]
3. Update known-first-party in isort config to match project package name
4. Update files in mypy config to match project source directories

Phase 3: Install Dependencies

Install required packages. Always install latest versions — no version pinning.

TypeScript:

npm install -D eslint @eslint/js typescript-eslint eslint-config-prettier prettier eslint-plugin-unicorn jiti

For React projects, also install: npm install -D eslint-plugin-react eslint-plugin-react-hooks

Note on jiti: Required for eslint.config.ts on Node.js < 22.10. On Node.js 22.10+ TypeScript configs are supported natively.

.NET:

• Analyzers included in SDK 5+ — no separate install needed

Python:

uv add --dev ruff mypy

# OR without uv:
pip install ruff mypy

Phase 4: Generate Lint Script

Generate scripts/lint.sh from lint_script_template.sh with checks for the detected stack.

1. Copy lint_script_template.sh to scripts/lint.sh
2. Uncomment the check lines matching the detected stack (Python/TypeScript/.NET)
3. Set TOTAL variable to match the number of active checks
4. Make file executable: chmod +x scripts/lint.sh
5. For TypeScript: ensure "lint:all" script exists in package.json

Phase 5: Verify Setup

After configuration, verify everything works.

TypeScript:

npx tsc --noEmit
npx eslint .
npx prettier --check .

.NET:

dotnet format --verify-no-changes

Python:

ruff check .
ruff format --check .
mypy

Unified verification:

bash scripts/lint.sh

Expected: Exit code 0 for all checks.

On Failure: Check error output, adjust config, re-verify.

Phase 6: Optional Advanced Tools

Suggest but do not auto-install. Inform user and add as commented lines in scripts/lint.sh.

Critical Rules

RULE 1: Always include eslint-config-prettier (last in config) when using ESLint + Prettier together.

RULE 2: Use ESLint flat config format (eslint.config.ts), NOT legacy .eslintrc.

RULE 3: Ruff replaces Black, isort, flake8, and many other Python tools. Do NOT install them separately.

RULE 4: Never disable strict TypeScript rules without documented reason.

RULE 5: Always run mypy alongside Ruff for Python projects. Ruff handles style/bugs, mypy handles type safety.

RULE 6: Use recommendedTypeChecked as ESLint default, not just recommended. Downgrade individual rules if needed.

RULE 7: Never pin dependency versions in install commands — always install latest.

Definition of Done

• Appropriate config files created for detected stack
• Dependencies installed (latest versions)
• scripts/lint.sh generated with correct checks for stack
• Lint command runs without errors on project source
• Format command runs without errors
• Type checker runs without errors (mypy for Python, tsc for TypeScript)
• No ESLint/Prettier conflicts (eslint-config-prettier installed)
• User informed of available lint/format commands and optional advanced tools

Reference Files

Error Handling

Version: 3.0.0 Last Updated: 2026-02-26