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flycheck-ocaml.el
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flycheck-ocaml.el
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;;; flycheck-ocaml.el --- Flycheck: OCaml support -*- lexical-binding: t; -*-
;; Copyright (C) 2014-2015 Sebastian Wiesner <swiesner@lunaryorn.com>
;; Copyright (C) 2015 Frédéric Bour <frederic.bour@lakaban.net>
;; Copyright (C) 2022 Bozhidar Batsov <bozhidar@batsov.dev>
;; Author: Sebastian Wiesner <swiesner@lunaryorn.com>
;; Maintainer: Bozhidar Batsov <bozhidar@batsov.dev>
;; URL: https://github.com/flycheck/flycheck-ocaml
;; Keywords: convenience, tools, languages, ocaml
;; Version: 0.4.2
;; Package-Requires: ((emacs "24.3") (flycheck "32") (merlin "3.0.1") (let-alist "1.0.3"))
;; This file is not part of GNU Emacs.
;; This program 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 of the License, or
;; (at your option) any later version.
;; This program 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.
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;; This Flycheck extension provides a new `ocaml-merlin' syntax checker which
;; uses Merlin Mode (see URL `https://github.com/ocaml/merlin') to
;; check OCaml buffers for errors.
;;
;; # Setup
;;
;; Add the following to your init file:
;;
;; (with-eval-after-load 'merlin
;; ;; Disable Merlin's own error checking
;; (setq merlin-error-after-save nil)
;;
;; ;; Enable Flycheck checker
;; (flycheck-ocaml-setup))
;;
;; (add-hook 'tuareg-mode-hook #'merlin-mode)
;;
;; # Usage
;;
;; Just use Flycheck as usual in Tuareg Mode buffers. Flycheck will
;; automatically use the new `ocaml-merlin` syntax checker if Merlin Mode is
;; enabled and Merlin's own error checking (`merlin-error-after-save`) is
;; disabled.
;;
;; If you enable Merlin's error checking with `M-x merlin-toggle-view-errors`
;; Flycheck will not use the `ocaml-merlin` syntax checker anymore, to avoid
;; duplicate and redundant error reporting.
;;; Code:
(eval-when-compile
(require 'let-alist))
(require 'merlin)
(require 'flycheck)
(defconst flycheck-ocaml-merlin-message-re
(rx string-start
;; Skip over leading spaces and punctuation
(zero-or-more (any punct space control))
;; Take the level...
(opt (: (group-n 1 (or "Warning" "Error"))
;; ...and skip over trailing digits (e.g. Warning 8:)
(zero-or-more (any space digit)) ": "))
;; The rest is the real error message
(group-n 2 (one-or-more anything)) string-end)
"Regular expression to parse a Merlin error message.")
(defun flycheck-ocaml-merlin-parse-message (message)
"Parse an error MESSAGE from a Merlin error.
Return `(LEVEL . PARSED-MESSAGE)', where LEVEL is the Flycheck
error level, and PARSED-MESSAGE is the real error message with
irrelevant parts removed."
(when (string-match flycheck-ocaml-merlin-message-re message)
(let ((level (pcase (match-string 1 message)
(`"Warning" 'warning)
((or `"Error" `nil) 'error)
(level (lwarn 'flycheck-ocaml :error
"Unknown error level %S" level)))))
(cons level (string-trim (match-string 2 message))))))
(defun flycheck-ocaml-merlin-parse-error (alist checker)
"Parse a Merlin error ALIST from CHECKER into a `flycheck-error'.
Return the corresponding `flycheck-error'."
(let-alist alist
(when .message
(pcase-let* ((`(,level . ,message)
(flycheck-ocaml-merlin-parse-message .message)))
;; OCaml columns seem to be zero-based, see
;; https://github.com/flycheck/flycheck-ocaml/issues/2
(flycheck-error-new-at (or .start.line 1)
(when .start.col (1+ .start.col))
(or level 'error) (or message .message)
:checker checker)))))
(defun flycheck-verify-ocaml-merlin (_checker)
"Verify the OCaml Merlin syntax checker."
(let ((command (executable-find (merlin-command)))
(dune-file (and buffer-file-name (locate-dominating-file buffer-file-name "dune-project"))))
(list
(flycheck-verification-result-new
:label "Merlin command"
:message (if command (format "Found at %s" command) "Not found")
:face (if command 'success '(bold error)))
(flycheck-verification-result-new
:label "Dune project"
:message (if dune-file (format "Found at %s" dune-file) "Not found")
:face (if dune-file 'success '(bold error)))
(flycheck-verification-result-new
:label "Merlin mode"
:message (if merlin-mode "enabled" "disabled")
:face (if merlin-mode 'success '(bold warning)))
(flycheck-verification-result-new
:label "Merlin error checking"
:message (if merlin-error-after-save "enabled" "disabled")
:face (if merlin-error-after-save '(bold warning) 'success)))))
(defun flycheck-ocaml-merlin-start (checker callback)
"Start a Merlin syntax check with CHECKER.
CALLBACK is the status callback passed by Flycheck."
(condition-case err
(let ((errors (delq nil
(mapcar
(lambda (alist)
(flycheck-ocaml-merlin-parse-error alist
checker))
(merlin-call "errors")))))
(funcall callback 'finished errors))
(error (funcall callback 'errored (error-message-string err)))))
(flycheck-define-generic-checker 'ocaml-merlin
"A syntax checker for OCaml using Merlin Mode.
See URL `https://github.com/ocaml/merlin'."
:start #'flycheck-ocaml-merlin-start
:verify #'flycheck-verify-ocaml-merlin
:modes '(caml-mode tuareg-mode reason-mode)
:predicate (lambda () (and merlin-mode
;; Don't check if there is not a 'dune-project'
;; present somewhere in the directory tree
(and buffer-file-name (locate-dominating-file buffer-file-name "dune-project"))
;; Don't check if Merlin's own checking is
;; enabled, to avoid duplicate overlays
(not merlin-error-after-save))))
;;;###autoload
(defun flycheck-ocaml-setup ()
"Setup Flycheck OCaml.
Add `ocaml-merlin' to `flycheck-checkers'."
(interactive)
(add-to-list 'flycheck-checkers 'ocaml-merlin))
(provide 'flycheck-ocaml)
;;; flycheck-ocaml.el ends here