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;;; blacken.el --- Reformat python buffers using the "black" formatter
;; Copyright (C) 2018-2019 Artem Malyshev
;; Author: Artem Malyshev <proofit404@gmail.com>
;; Homepage: https://github.com/proofit404/blacken
;; Version: 0.0.1
;; Package-Version: 20191123.1547
;; Package-Requires: ((emacs "25.2"))
;; This file is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published
;; by the Free Software Foundation; either version 3, or (at your
;; option) any later version.
;;
;; This file is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;;
;; For a full copy of the GNU General Public License
;; see <http://www.gnu.org/licenses/>.
;;; Commentary:
;;
;; Blacken uses black to format a Python buffer. It can be called
;; explicitly on a certain buffer, but more conveniently, a minor-mode
;; 'blacken-mode' is provided that turns on automatically running
;; black on a buffer before saving.
;;
;; Installation:
;;
;; Add blacken.el to your load-path.
;;
;; To automatically format all Python buffers before saving, add the
;; function blacken-mode to python-mode-hook:
;;
;; (add-hook 'python-mode-hook 'blacken-mode)
;;
;;; Code:
(require 'cl-lib)
(defgroup blacken nil
"Reformat Python code with \"black\"."
:group 'python)
(defcustom blacken-executable "black"
"Name of the executable to run."
:type 'string)
(defcustom blacken-line-length nil
"Line length to enforce.
It must be an integer, nil or `fill'.
If `fill', the `fill-column' variable value is used."
:type '(choice :tag "Line Length Limit"
(const :tag "Use default" nil)
(const :tag "Use fill-column" fill)
(integer :tag "Line Length"))
:safe 'integerp)
(defcustom blacken-allow-py36 nil
"Allow using Python 3.6-only syntax on all input files."
:type 'boolean
:safe 'booleanp)
(defcustom blacken-skip-string-normalization nil
"Don't normalize string quotes or prefixes."
:type 'boolean
:safe 'booleanp)
(defcustom blacken-fast-unsafe nil
"Skips temporary sanity checks."
:type 'boolean
:safe 'booleanp)
(defcustom blacken-only-if-project-is-blackened nil
"Only blacken if project has a pyproject.toml with a [tool.black] section."
:type 'boolean
:safe 'booleanp)
(defun blacken-call-bin (input-buffer output-buffer error-buffer)
"Call process black.
Send INPUT-BUFFER content to the process stdin. Saving the
output to OUTPUT-BUFFER. Saving process stderr to ERROR-BUFFER.
Return black process the exit code."
(with-current-buffer input-buffer
(let ((process (make-process :name "blacken"
:command `(,blacken-executable ,@(blacken-call-args))
:buffer output-buffer
:stderr error-buffer
:noquery t
:sentinel (lambda (process event)))))
(set-process-query-on-exit-flag (get-buffer-process error-buffer) nil)
(set-process-sentinel (get-buffer-process error-buffer) (lambda (process event)))
(save-restriction
(widen)
(process-send-region process (point-min) (point-max)))
(process-send-eof process)
(accept-process-output process nil nil t)
(while (process-live-p process)
(accept-process-output process nil nil t))
(process-exit-status process))))
(defun blacken-call-args ()
"Build black process call arguments."
(append
(when blacken-line-length
(list "--line-length"
(number-to-string (cl-case blacken-line-length
('fill fill-column)
(t blacken-line-length)))))
(when blacken-allow-py36
(list "--py36"))
(when blacken-fast-unsafe
(list "--fast"))
(when blacken-skip-string-normalization
(list "--skip-string-normalization"))
(when (and (buffer-file-name (current-buffer))
(string-match "\.pyi$" (buffer-file-name (current-buffer))))
(list "--pyi"))
'("-")))
(defun blacken-project-is-blackened (&optional display)
"Whether the project has a pyproject.toml with [tool.black] in it."
(when-let ((parent (locate-dominating-file default-directory "pyproject.toml")))
(with-temp-buffer
(insert-file-contents (concat parent "pyproject.toml"))
(re-search-forward "^\\[tool.black\\]$" nil t 1))))
;;;###autoload
(defun blacken-buffer (&optional display)
"Try to blacken the current buffer.
Show black output, if black exit abnormally and DISPLAY is t."
(interactive (list t))
(let* ((original-buffer (current-buffer))
(original-point (point))
(original-window-pos (window-start))
(tmpbuf (get-buffer-create "*blacken*"))
(errbuf (get-buffer-create "*blacken-error*")))
;; This buffer can be left after previous black invocation. It
;; can contain error message of the previous run.
(dolist (buf (list tmpbuf errbuf))
(with-current-buffer buf
(erase-buffer)))
(condition-case err
(if (not (zerop (blacken-call-bin original-buffer tmpbuf errbuf)))
(error "Black failed, see %s buffer for details" (buffer-name errbuf))
(unless (eq (compare-buffer-substrings tmpbuf nil nil original-buffer nil nil) 0)
(with-current-buffer tmpbuf
(copy-to-buffer original-buffer (point-min) (point-max)))
(goto-char original-point)
(set-window-start (selected-window) original-window-pos))
(mapc 'kill-buffer (list tmpbuf errbuf)))
(error (message "%s" (error-message-string err))
(when display
(with-current-buffer errbuf
(setq-local scroll-conservatively 0))
(pop-to-buffer errbuf))))))
;;;###autoload
(define-minor-mode blacken-mode
"Automatically run black before saving."
:lighter " Black"
(if blacken-mode
(when (or (not blacken-only-if-project-is-blackened)
(blacken-project-is-blackened))
(add-hook 'before-save-hook 'blacken-buffer nil t))
(remove-hook 'before-save-hook 'blacken-buffer t)))
(provide 'blacken)
;;; blacken.el ends here
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