Re: [PATCH] Add json-sexp-mode.

[Taylan Ulrich Bayırlı/Kammer]

Artur Malabarba <address@hidden> writes:

> 2015-10-17 19:10 GMT+01:00 Taylan Ulrich Bayırlı/Kammer
> <address@hidden>:
>>
>> json.el yields Elisp s-expressions though.  The closest approximation to
>> an "Elisp s-expression editing mode" is emacs-lisp-mode.
>
> I've got something even better for you then. You can change your mode
> to inherit from prog-mode and add this line:
>     (lisp-mode-variables nil nil 'elisp)
>
> This should make sure it has all the syntax definitions of
> emacs-lisp-mode, without carrying its keybinds, eldoc, completion
> functions, xref definitions, search-path, menu-bars, etc, which (IIUC)
> wouldn't make sense for this json-sexp-mode.
>
> Of course, it's up to you. I'm just recommending what I would do.

Ooh, thanks, that seems to be a good way to do it.

(Some people might have to add paredit-mode to json-sexp-mode-hook when
previously emacs-lisp-mode-hook would enable it for them, but that
should be fine.  I personally enable Paredit in prog-mode-hook.)

Here's the updated patch.

>From ff35fbca2ff8b818ce47efe2bb1d07f5f70a6051 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Taylan=20Ulrich=20Bay=C4=B1rl=C4=B1/Kammer?=
 <address@hidden>
Date: Sat, 17 Oct 2015 17:15:23 +0200
Subject: [PATCH 1/2] Add json-sexp-mode.

---
 packages/json-sexp-mode/json-sexp-mode.el | 110 ++++++++++++++++++++++++++++++
 1 file changed, 110 insertions(+)
 create mode 100644 packages/json-sexp-mode/json-sexp-mode.el

diff --git a/packages/json-sexp-mode/json-sexp-mode.el 
b/packages/json-sexp-mode/json-sexp-mode.el
new file mode 100644
index 0000000..689ba8c
--- /dev/null
+++ b/packages/json-sexp-mode/json-sexp-mode.el
@@ -0,0 +1,110 @@
+;;; json-sexp-mode.el --- Edit JSON in s-expression form.
+
+;; Copyright (C) 2015  Free Software Foundation, Inc.
+
+;; Author: Taylan Ulrich Bayırlı/Kammer <address@hidden>
+;; Keywords: data, files
+
+;; 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:
+
+;; Activating `json-sexp-mode' will turn the JSON value in the buffer into an
+;; s-expression, and arrange for it to be transparently converted back into a
+;; (pretty-printed) JSON value whenever the buffer is saved.  Adding
+;; `json-sexp-mode' to `auto-mode-alist' can provide a fully transparent
+;; experience for editing JSON files as s-expressions.
+;;
+;; The symbol `false' is used to represent JSON's false value, because nil
+;; stands for an empty object.  (However, t is used for JSON's true value.)
+;;
+;;
+;; The following commands can be used to manually convert a region or whole
+;; buffer from a JSON value to an s-expression and from an s-expression to a
+;; JSON value:
+;;
+;; `json-sexp-convert-region-to-sexp'
+;; `json-sexp-convert-region-to-json'
+;; `json-sexp-convert-buffer-to-sexp'
+;; `json-sexp-convert-buffer-to-json'
+
+;;; Code:
+(require 'json)
+
+(defun json-sexp-convert-region-to-sexp (start end)
+  "Convert region from JSON to sexps."
+  (interactive "r")
+  (unless (= start end)
+    (let ((data (let ((json-object-type 'alist)
+                      (json-false 'false)
+                      (json-null 'null))
+                  (json-read-from-string (buffer-substring start end))))
+          (point (point)))
+      (delete-region start end)
+      (goto-char start)
+      (insert (pp-to-string data))
+      ;; Only an approximation of our position in the JSON.
+      (goto-char point))))
+
+(defun json-sexp-convert-region-to-json (start end)
+  "Convert region from sexps to JSON."
+  (interactive "r")
+  (unless (= start end)
+    (let ((data (car (read-from-string (buffer-substring start end))))
+          (point (point)))
+      (delete-region start end)
+      (goto-char start)
+      (insert (let ((json-encoding-pretty-print t)
+                    (json-false 'false)
+                    (json-null 'null)
+                    (json-nil 'object))
+                (json-encode data)))
+      ;; Only an approximation of our position in the s-expression.
+      (goto-char point))))
+
+(defun json-sexp-convert-buffer-to-sexp ()
+  "Convert buffer from JSON to sexps."
+  (interactive)
+  (json-sexp-convert-region-to-sexp (point-min) (point-max)))
+
+(defun json-sexp-convert-buffer-to-json ()
+  "Convert buffer from sexps to JSON."
+  (interactive)
+  (json-sexp-convert-region-to-json (point-min) (point-max)))
+
+(defvar json-sexp--saved-point nil)
+
+(define-derived-mode json-sexp-mode prog-mode "JSON-sexp"
+  "Major mode for editing JSON in s-expression form.
+The buffer-contents, which must be JSON, are transformed to
+s-expressions when this mode is started, and transformed back
+temporarily to JSON whenever the buffer is saved."
+  (lisp-mode-variables nil nil 'elisp)
+  (let ((was-modified (buffer-modified-p)))
+    (json-sexp-convert-buffer-to-sexp)
+    (set-buffer-modified-p was-modified))
+  (add-hook 'before-save-hook 'json-sexp--before-save nil t)
+  (add-hook 'after-save-hook 'json-sexp--after-save nil t))
+
+(defun json-sexp--before-save ()
+  (setq json-sexp--saved-point (point))
+  (json-sexp-convert-buffer-to-json))
+
+(defun json-sexp--after-save ()
+  (json-sexp-convert-buffer-to-sexp)
+  (set-buffer-modified-p nil)
+  (goto-char json-sexp--saved-point))
+
+(provide 'json-sexp-mode)
+;;; json-sexp-mode.el ends here
-- 
2.5.0