Emacs から Ruff を使う

pipx install ruff

# 公式ドキュメント通り、pip でインストールするなら
# pip install ruff

# cache-dir
cache-dir = "~/.cache/ruff"

# Exclude a variety of commonly ignored directories.
exclude = [
    ".bzr",
    ".direnv",
    ".eggs",
    ".git",
    ".git-rewrite",
    ".hg",
    ".mypy_cache",
    ".nox",
    ".pants.d",
    ".pytype",
    ".ruff_cache",
    ".svn",
    ".tox",
    ".venv",
    "__pypackages__",
    "_build",
    "buck-out",
    "build",
    "dist",
    "node_modules",
    "venv",
]

line-length = 300
indent-width = 4


[lint]
select = ["ALL"]
ignore = ["E501", "PGH", "DJ", "D", "T20", "ERA", "C90", "ANN101", "FA102", "RUF001", "PLR0915", "S101", "S311", "S104"]

fixable = ["I", "SIM118"]
unfixable = []

[format]
# Like Black, use double quotes for strings.
quote-style = "double"

# Like Black, indent with spaces, rather than tabs.
indent-style = "space"

# Like Black, respect magic trailing commas.
skip-magic-trailing-comma = false

# Like Black, automatically detect the appropriate line ending.
line-ending = "auto"

# lintエラーの表示
ruff check test.py

# 自動修正可能なlintエラーの修正
ruff check --fix test.py

# コードフォーマットを適用
ruff format test.py

(use-package flymake-ruff
  :ensure t
  :hook (eglot-managed-mode-hook . (lambda ()
                                     (when (derived-mode-p 'python-mode 'python-ts-mode)
                                       (flymake-ruff-load))))
  :config
  (setq flymake-ruff--default-configs '("ruff.toml" ".ruff.toml")))

(use-package reformatter
  :hook
  (python-ts-mode-hook . ruff-format-on-save-mode)
  :config
  (reformatter-define ruff-format
    :program "ruff"
    :args `("format" "--stdin-filename" ,buffer-file-name "-")))

(defun ruff-fix-buffer ()
  "Use ruff to fix lint violations in the current buffer."
  (interactive)
  (let* ((temporary-file-directory (if (buffer-file-name)
                                       (file-name-directory (buffer-file-name))
                                     temporary-file-directory))
         (temporary-file-name-suffix (format "--%s" (if (buffer-file-name)
                                                                 (file-name-nondirectory (buffer-file-name))
                                                                "")))
         (temp-file (make-temp-file "temp-ruff-" nil temporary-file-name-suffix))
         (current-point (point)))
    (write-region (point-min) (point-max) temp-file nil)
    (shell-command-to-string (format "ruff check --fix %s" temp-file))
    (erase-buffer)
    (insert-file-contents temp-file)
    (delete-file temp-file)
    (goto-char current-point)))

(defun ruff-fix-before-save ()
  (interactive)
  (when (memq major-mode '(python-mode python-ts-mode))
    (ruff-fix-buffer)))

(add-hook 'before-save-hook 'ruff-fix-before-save)