ln-741-linter-configurator

name	ln-741-linter-configurator
description	Configures ESLint, Prettier, Ruff, mypy, and .NET analyzers. Use when setting up linting and formatting for a project.
license	MIT
model	claude-sonnet-4-6

Paths: File paths (references/, ../ln-*) are relative to this skill directory.

ln-741-linter-configurator

Type: L3 Worker Category: 7XX Project Bootstrap

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

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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 (separate worker)
• Set up test infrastructure (separate worker)
• Modify source code

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Supported Stacks

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

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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
Python	mypy config	mypy.toml, mypy.ini, pyproject.toml [tool.mypy]

Decision Logic:

1. If no config exists: CREATE from template
2. If config exists but incomplete (fewer rules/tools than template): EXTEND to match template
3. If config matches template: SKIP (inform user)

Completeness Check (Python):

Aspect	Check	Template Standard
Ruff rules	Count select entries	23+ categories (see ruff_template.toml)
Ruff per-file-ignores	Tests section exists	tests/**/*.py with S101,S105,S106,T201
Ruff advanced	mccabe, flake8-bugbear, isort	All present
MyPy	strict = true	Enabled
Advanced tools	import-linter, deptry, vulture in dev deps	All installed
Lint script	scripts/lint.sh with 7 checks	All 7 active
.editorconfig	File exists	Present

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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
5. Generate advanced tool configs in pyproject.toml:
   • [tool.importlinter] from importlinter_template.toml -- adapt root_packages and contracts to project layer structure
   • [tool.vulture] from vulture_template.toml -- adapt paths to project source directory
   • [tool.deptry] from deptry_template.toml -- adapt extend_exclude
6. Generate .editorconfig from editorconfig_template.ini -- adapt max_line_length to match ruff line-length

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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 import-linter deptry vulture pip-audit

# OR without uv:
pip install ruff mypy import-linter deptry vulture pip-audit

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Phase 4: Generate Lint Script

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

1. Copy lint_script_template.sh to scripts/lint.sh
2. Uncomment ALL check lines matching detected stack -- both basic AND advanced tools:

Stack	Checks	TOTAL
Python	ruff check, ruff format, mypy, lint-imports, deptry, vulture, pip-audit	7
TypeScript	typecheck, eslint, prettier, knip, depcruise	5
.NET	dotnet build, dotnet format	2

3. Set TOTAL to match active checks count
4. Uncomment matching auto-fix commands in --fix block
5. Make executable: chmod +x scripts/lint.sh
6. For TypeScript: ensure "lint:all" script exists in package.json

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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.

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Phase 6: Fix Lint Errors

After generating all configs and installing tools, run bash scripts/lint.sh --all to see all violations.

1. Run bash scripts/lint.sh --fix to auto-fix what ruff can
2. Fix remaining errors manually (file by file)
3. For C901 (complexity) on functions that cannot be refactored now: add # noqa: C901
4. For deptry false positives: add [tool.deptry.per_rule_ignores] entries
5. Repeat until bash scripts/lint.sh passes with 0 failures

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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.

RULE 8: Advanced static analysis tools (import-linter, deptry, vulture, pip-audit) are MANDATORY for Python projects, not optional.

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Monitor (2.1.98+): When lint/typecheck verification commands expected >30s, use Monitor. Fallback: Bash(run_in_background=true).

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)
• Advanced tools installed and configured (import-linter, deptry, vulture, pip-audit)
• scripts/lint.sh runs ALL checks (7 for Python) with exit code 0
• .editorconfig created with settings matching ruff config
• User informed of available lint/format commands

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Reference Files

File	Purpose
eslint_template.ts	ESLint flat config template (TypeScript)
prettier_template.json	Prettier config template
ruff_template.toml	Python Ruff config template
mypy_template.toml	Python mypy config template
lint_script_template.sh	Unified lint script template
editorconfig_template.ini	.NET editorconfig template
directory_build_props_template.xml	.NET analyzers template
importlinter_template.toml	Python import-linter config template
vulture_template.toml	Python vulture config template
deptry_template.toml	Python deptry config template
linter_guide.md	Detailed configuration guide

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Error Handling

Error	Cause	Resolution
ESLint/Prettier conflict	Missing eslint-config-prettier	Install and add as last config
ESLint projectService error	Config file not in tsconfig	Add to allowDefaultProject list
ESLint .ts config fails	Missing jiti	npm install -D jiti
TypeScript parse errors	Parser version mismatch	Align typescript-eslint with TS version
mypy missing stubs	Third-party library without types	Add [[mypy.overrides]] with ignore_missing_imports
mypy strict too strict	Hundreds of errors on first run	Start with relaxed config, enable strict gradually
Ruff not found	Not installed	pip install ruff or uv add ruff
dotnet format fails	Missing SDK	Install .NET SDK

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Version: 4.0.0 Last Updated: 2026-03-18