smellcheck 0.2.3

Python code smell detector -- 82 refactoring patterns, 55 AST checks, zero dependencies

smellcheck

Python Code Smell Detector & Refactoring Guide
82 refactoring patterns · 55 automated AST checks · zero dependencies

smellcheck is a Python code smell detector and refactoring catalog. It works as a pip-installable CLI, GitHub Action, pre-commit hook, or Agent Skills plugin for AI coding assistants.

No dependencies. Pure Python stdlib (ast, pathlib, json). Runs anywhere Python 3.10+ runs.

Installation

pip

pip install smellcheck

smellcheck src/
smellcheck myfile.py --format json
smellcheck src/ --min-severity warning --fail-on warning

GitHub Action

- uses: cheickmec/smellcheck@v1
  with:
    paths: 'src/'
    fail-on: 'error'       # exit 1 on error-level findings (default)
    min-severity: 'info'   # display all findings (default)
    format: 'github'       # GitHub annotations (default)

pre-commit

repos:
  - repo: https://github.com/cheickmec/smellcheck
    rev: v0.2.0
    hooks:
      - id: smellcheck
        args: ['--fail-on', 'warning']

Agent Skills (Claude Code, Codex CLI, Cursor, Copilot, Roo Code, Gemini CLI)

Any tool supporting the Agent Skills standard can install directly:

# Claude Code
/plugin marketplace add cheickmec/smellcheck
/plugin install python-refactoring@smellcheck

# OpenAI Codex CLI
$skill-installer install cheickmec/smellcheck

# Cursor
# Import from GitHub URL in skills settings

# Or install from a local clone
git clone https://github.com/cheickmec/smellcheck.git
# Point your tool to plugins/python-refactoring/skills/python-refactoring/

Manual setup for other tools

For tools without Agent Skills support (Aider, Windsurf, Continue.dev, Amazon Q), copy the relevant files into your project's instruction directory:

• Copy SKILL.md content into your tool's instruction file (.cursorrules, CONVENTIONS.md, .windsurf/rules/, etc.)
• Install with pip install smellcheck and run the smellcheck CLI

Usage

# Scan a directory
smellcheck src/

# Scan multiple files
smellcheck file1.py file2.py

# JSON output
smellcheck src/ --format json

# GitHub Actions annotations
smellcheck src/ --format github

# Filter by severity
smellcheck src/ --min-severity warning

# Control exit code
smellcheck src/ --fail-on warning   # exit 1 on warning or error
smellcheck src/ --fail-on info      # exit 1 on any finding

# Run only specific checks
smellcheck src/ --select 001,057,CC

# Skip specific checks
smellcheck src/ --ignore 003,006

# Module execution
python -m smellcheck src/

Configuration

smellcheck reads [tool.smellcheck] from the nearest pyproject.toml:

[tool.smellcheck]
select = ["001", "002", "057"]       # only run these checks (default: all)
ignore = ["003", "006"]              # skip these checks
per-file-ignores = {"tests/*" = ["002", "034"]}  # per-path overrides
fail-on = "warning"                  # override default fail-on
format = "text"                      # override default format

CLI flags override config values.

Inline Suppression

Add # noqa: SC057 to a line to suppress pattern #057 on that line:

def foo(x=[]):  # noqa: SC057
    return x

Use # noqa (no codes) to suppress all findings on that line. Multiple codes: # noqa: SC003,SC006

Features

• 55 automated smell checks -- per-file AST analysis, cross-file dependency analysis, and OO metrics
• 82 refactoring patterns -- numbered catalog with before/after examples, trade-offs, and severity levels
• Zero dependencies -- stdlib-only, runs on any Python 3.10+ installation
• Multiple output formats -- text (terminal), JSON (machine-readable), GitHub annotations (CI)
• Configurable -- pyproject.toml config, inline suppression, CLI overrides
• Four distribution channels -- pip, GitHub Action, pre-commit, Agent Skills

Detected Patterns

Per-File (40 checks)

#	Pattern	Severity
001	Setters (half-built objects)	warning
002	Long functions (>20 lines)	warning
003	Magic numbers	info
004	Bare except / unused exception variable	warning
006	Generic names (data, result, tmp)	info
007	Extract class (too many methods)	info
008	UPPER_CASE without Final	info
009	Unprotected public attributes	info
014	isinstance chains	warning
016	Half-built objects (init assigns None)	warning
017	Boolean flag parameters	info
018	Singleton pattern	warning
021	Dead code after return	warning
024	Global mutable state	warning
026	input() in business logic	warning
028	Sequential IDs	info
029	Functions returning None or list	info
033	Excessive decorators (>3)	info
034	Too many parameters (>5)	warning
036	String concatenation for multiline	info
039	Deep nesting (>4 levels)	warning
040	Loop + append pattern	info
041	CQS violation (query + modify)	warning
042	Complex boolean expressions	warning
051	Error codes instead of exceptions	warning
054	Law of Demeter violation	info
055	Boolean control flag in loop	info
057	Mutable default arguments	error
058	open() without context manager	warning
061	Dataclass candidate	info
062	Sequential tuple indexing	info
063	contextlib candidate	info
CC	Cyclomatic complexity (>10)	warning
064	Unused function parameters	warning
065	Empty catch block	warning
066	Long lambda (>60 chars)	info
067	Complex comprehension (>2 generators)	warning
068	Missing default else branch	info
069	Lazy class (<2 methods)	info
070	Temporary fields	warning

Cross-File (10 checks)

#	Pattern	Description
013	Duplicate functions	AST-normalized hashing across files
CYC	Cyclic imports	DFS cycle detection
GOD	God modules	>500 lines or >30 top-level definitions
FE	Feature envy	Function accesses external attributes more than own
SHO	Shotgun surgery	Function called from >5 different files
DIT	Deep inheritance	Inheritance depth >4
WHI	Wide hierarchy	>5 direct subclasses
INT	Inappropriate intimacy	>3 bidirectional class references between files
SPG	Speculative generality	Abstract class with no concrete subclasses
UDE	Unstable dependency	Stable module depends on unstable module

OO Metrics (5 checks)

#	Metric	Threshold
LCOM	Lack of Cohesion of Methods	>0.8
CBO	Coupling Between Objects	>8
FIO	Excessive Fan-Out	>15
RFC	Response for a Class	>20
MID	Middle Man (delegation ratio)	>50%

Refactoring Reference Files

Each pattern includes a description, before/after code examples, and trade-offs:

File	Patterns
state.md	Immutability, setters, attributes (001, 008, 009, 016, 017, 030)
functions.md	Extraction, naming, parameters, CQS (002, 010, 020, 026, 027, 034, 037, 041, 050, 052, 064, 066)
types.md	Classes, reification, polymorphism, nulls (007, 012, 014, 015, 019, 022, 023, 029, 038, 044, 048, 069, 070, DIT, WHI)
control.md	Guards, pipelines, conditionals, phases (039-043, 046, 047, 049, 053, 055, 056, 067, 068)
architecture.md	DI, singletons, exceptions, delegates (018, 024, 028, 035, 045, 051, 054, SHO, INT, SPG, UDE)
hygiene.md	Constants, dead code, comments, style (003, 004, 011, 013, 021, 025, 031-033, 036, 065)
idioms.md	Context managers, generators, unpacking (057-063)
metrics.md	OO metrics: cohesion, coupling, fan-out, response, delegation (LCOM, CBO, FIO, RFC, MID)

Compatibility

Tool	Install Method	Status
pip	pip install smellcheck	Native support
GitHub Actions	uses: cheickmec/smellcheck@v1	Native support
pre-commit	.pre-commit-config.yaml	Native support
Claude Code	/plugin install	Native support
OpenAI Codex CLI	$skill-installer	Native support
Cursor	GitHub import / .cursor/skills/	Native support
GitHub Copilot	MCP gallery	Native support
Roo Code	.roo/ directory	Native support
Gemini CLI	Agent Skills	Native support
Windsurf	Copy to .windsurf/rules/	Manual
Aider	--read CONVENTIONS.md	Manual
Continue.dev	.continue/rules/	Manual
Amazon Q	.amazonq/rules/	Manual

How It Compares

Feature	smellcheck	PyExamine	SMART-Dal	Pyscent
Automated detections	55	49	31	11
Refactoring guidance	82 patterns	None	None	None
Dependencies	0 (stdlib)	pylint, radon	DesigniteJava	pylint, radon, cohesion
Python-specific idioms	Yes	No	No	No
Cross-file analysis	Yes	Limited	Yes	No
OO metrics	6	19	0	1
Distribution channels	4 (pip, GHA, pre-commit, Agent Skills)	1	1	1

Contributing

Contributions welcome. The core detector is src/smellcheck/detector.py -- add new checks by extending the SmellDetector AST visitor class and adding a cross-file analysis function if needed.

# Development setup
git clone https://github.com/cheickmec/smellcheck.git
cd smellcheck
pip install -e .
pip install pytest

# Run tests
pytest tests/ -v

# Self-check
smellcheck src/smellcheck/

License

MIT