Agent Skills: ln-741-linter-configurator

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ln-741-linter-configurator

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

Configures code linting and formatting tools for TypeScript, .NET, and Python 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
• Verifies linter runs 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

| Technology | Linter | Formatter | Config Files | |------------|--------|-----------|--------------| | TypeScript/React | ESLint 9+ (flat config) | Prettier | eslint.config.mjs, .prettierrc | | .NET | Roslyn Analyzers | dotnet format | .editorconfig, Directory.Build.props | | Python | Ruff | Ruff (built-in) | ruff.toml or pyproject.toml |

Phase 1: Check Existing Configuration

Before generating configs, check what already exists.

Files to Check:

| Stack | Config Files | Glob Pattern | |-------|--------------|--------------| | TypeScript | ESLint config | eslint.config.*, .eslintrc* | | TypeScript | Prettier config | .prettierrc*, prettier.config.* | | .NET | Editor config | .editorconfig | | .NET | Build props | Directory.Build.props | | Python | Ruff config | ruff.toml, pyproject.toml |

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/React:

1. Copy eslint_template.mjs to project root as eslint.config.mjs
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 ."

.NET:

1. Copy editorconfig_template.ini as .editorconfig
2. Copy directory_build_props_template.xml as Directory.Build.props
3. Ensure analyzers package reference included

Python:

1. Copy ruff_template.toml as ruff.toml
   • OR merge into existing pyproject.toml under [tool.ruff]
2. Add scripts to pyproject.toml or document commands

Phase 3: Install Dependencies

Install required packages for each stack.

TypeScript/React:

npm install -D eslint @eslint/js typescript-eslint eslint-plugin-react eslint-plugin-react-hooks eslint-config-prettier prettier

CRITICAL: eslint-config-prettier is REQUIRED to prevent ESLint/Prettier conflicts.

.NET:

• Analyzers configured via Directory.Build.props
• No separate install needed

Python:

pip install ruff
# OR with uv:
uv add --dev ruff

Phase 4: Verify Setup

After configuration, verify linter works.

TypeScript:

npm run lint
npm run format:check

Expected: Exit code 0

.NET:

dotnet format --verify-no-changes

Expected: Exit code 0

Python:

ruff check .
ruff format --check .

Expected: Exit code 0

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

Critical Rules

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

RULE 2: Use ESLint flat config format (eslint.config.mjs), 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.

Definition of Done

• [ ] Appropriate config files created for detected stack
• [ ] Dependencies installed
• [ ] Lint command runs without errors on project source
• [ ] Format command runs without errors
• [ ] No ESLint/Prettier conflicts (eslint-config-prettier installed)
• [ ] User informed of available lint/format commands

Reference Files

| File | Purpose | |------|---------| | eslint_template.mjs | ESLint flat config template | | prettier_template.json | Prettier config template | | editorconfig_template.ini | .NET editorconfig template | | directory_build_props_template.xml | .NET analyzers template | | ruff_template.toml | Python Ruff config template | | linter_guide.md | Detailed configuration guide |

Error Handling

| Error | Cause | Resolution | |-------|-------|------------| | ESLint/Prettier conflict | Missing eslint-config-prettier | Install and add to config | | TypeScript parse errors | Parser version mismatch | Align typescript-eslint with TS version | | Ruff not found | Not installed | pip install ruff or uv add ruff | | dotnet format fails | Missing SDK | Install .NET SDK |

Version: 2.0.0 Last Updated: 2026-01-10