bug#57884: [PATCH] Flymake backend using the shellcheck program

[Augusto Stoffel <arstoffel@gmail.com>]

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On Sun, 18 Sep 2022 at 21:18, Philip Kaludercic wrote:

> I just tried it out and it behaves the way you advertised it.

Could someone merge this patch then, so it gets some testing before
Emacs 29 is cut?

I've attached the patch again for your reference.


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From 49fbfaf98cb6d11b877eaa4a72b116aa61646d75 Mon Sep 17 00:00:00 2001
From: Augusto Stoffel <arstoffel@gmail.com>
Date: Sat, 17 Sep 2022 18:30:04 +0200
Subject: [PATCH] New Flymake backend using the shellcheck program

See bug#57884.

* lisp/progmodes/sh-script.el: Require let-alist and subr-x when
compiling.
(sh--json-read): Helper function to deal with possible absence of
json-parse-buffer.
(sh-shellcheck-program, sh--shellcheck-process,
sh-shellcheck-flymake): Variables and function defining a Flymake
backend.
(sh-mode): Add it to 'flymake-diagnostic-functions'.
---
 etc/NEWS                    |  4 ++
 lisp/progmodes/sh-script.el | 90 ++++++++++++++++++++++++++++++++++++-
 2 files changed, 93 insertions(+), 1 deletion(-)

diff --git a/etc/NEWS b/etc/NEWS
index a6a8883593..5b2ed16063 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1320,6 +1320,10 @@ This controls how statements like the following are indented:
     foo &&
         bar
 
+*** New Flymake backend using the ShellCheck program
+It is enabled by default, but requires that the external "shellcheck"
+command is installed.
+
 ** Cperl Mode
 
 ---
diff --git a/lisp/progmodes/sh-script.el b/lisp/progmodes/sh-script.el
index 517fbbd8e7..558b62b20a 100644
--- a/lisp/progmodes/sh-script.el
+++ b/lisp/progmodes/sh-script.el
@@ -31,6 +31,9 @@
 ;; available for filenames, variables known from the script, the shell and
 ;; the environment as well as commands.
 
+;; A Flymake backend using the "shellcheck" program is provided.  See
+;; https://www.shellcheck.net/ for installation instructions.
+
 ;;; Known Bugs:
 
 ;; - In Bourne the keyword `in' is not anchored to case, for, select ...
@@ -141,7 +144,9 @@
 (eval-when-compile
   (require 'skeleton)
   (require 'cl-lib)
-  (require 'comint))
+  (require 'comint)
+  (require 'let-alist)
+  (require 'subr-x))
 (require 'executable)
 
 (autoload 'comint-completion-at-point "comint")
@@ -1580,6 +1585,7 @@ sh-mode
 	 ((equal (file-name-nondirectory buffer-file-name) ".profile") "sh")
          (t sh-shell-file))
    nil nil)
+  (add-hook 'flymake-diagnostic-functions #'sh-shellcheck-flymake nil t)
   (add-hook 'hack-local-variables-hook
     #'sh-after-hack-local-variables nil t))
 
@@ -3103,6 +3109,88 @@ sh-delete-backslash
  	    (delete-region (1+ (point))
  			   (progn (skip-chars-backward " \t") (point)))))))
 
+;;; Flymake backend
+
+(defcustom sh-shellcheck-program "shellcheck"
+  "Name of the shellcheck executable."
+  :type 'string
+  :version "29.1")
+
+(defcustom sh-shellcheck-arguments nil
+  "Additional arguments to the shellcheck program."
+  :type '(repeat string)
+  :version "29.1")
+
+(defvar-local sh--shellcheck-process nil)
+
+(defalias 'sh--json-read
+  (if (fboundp 'json-parse-buffer)
+      (lambda () (json-parse-buffer :object-type 'alist))
+    (require 'json)
+    'json-read))
+
+(defun sh-shellcheck-flymake (report-fn &rest _args)
+  "Flymake backend using the shellcheck program.
+Takes a Flymake callback REPORT-FN as argument, as expected of a
+member of `flymake-diagnostic-functions'."
+  (when (process-live-p sh--shellcheck-process)
+    (kill-process sh--shellcheck-process))
+  (let* ((source (current-buffer))
+         (dialect (named-let recur ((s sh-shell))
+                    (pcase s
+                      ((or 'bash 'dash 'sh) (symbol-name s))
+                      ('ksh88 "ksh")
+                      ((guard s)
+                       (recur (alist-get s sh-ancestor-alist))))))
+         (sentinel
+          (lambda (proc _event)
+            (when (memq (process-status proc) '(exit signal))
+              (unwind-protect
+                  (if (with-current-buffer source
+                        (not (eq proc sh--shellcheck-process)))
+                      (flymake-log :warning "Canceling obsolete check %s" proc)
+                    (with-current-buffer (process-buffer proc)
+                      (goto-char (point-min))
+                      (thread-last
+                        (sh--json-read)
+                        (alist-get 'comments)
+                        (seq-filter
+                         (lambda (item)
+                           (let-alist item (string= .file "-"))))
+                        (mapcar
+                         (lambda (item)
+                           (let-alist item
+                             (flymake-make-diagnostic
+                              source
+                              (cons .line .column)
+                              (unless (and (eq .line .endLine)
+                                           (eq .column .endColumn))
+                                (cons .endLine .endColumn))
+                              (pcase .level
+                                ("error" :error)
+                                ("warning" :warning)
+                                (_ :note))
+                              (format "SC%s: %s" .code .message)))))
+                        (funcall report-fn))))
+                (kill-buffer (process-buffer proc)))))))
+    (unless dialect
+      (error "`sh-shellcheck-flymake' is not suitable for shell type `%s'"
+             sh-shell))
+    (setq sh--shellcheck-process
+          (make-process
+           :name "shellcheck" :noquery t :connection-type 'pipe
+           :buffer (generate-new-buffer " *flymake-shellcheck*")
+           :command `(,sh-shellcheck-program
+                      "--format=json1"
+                      "-s" ,dialect
+                      ,@sh-shellcheck-arguments
+                      "-")
+           :sentinel sentinel))
+    (save-restriction
+      (widen)
+      (process-send-region sh--shellcheck-process (point-min) (point-max))
+      (process-send-eof sh--shellcheck-process))))
+
 (provide 'sh-script)
 
 ;;; sh-script.el ends here
-- 
2.37.3


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Thanks!