[sql] Add sqlfmt-region command, bindings; enhance customize options

Enhances `sqlfmt` support in SQL layer.

`sqlfmt` was only being applied against the whole buffer, and did not allow
invocation against a specific region in the buffer. `sqlfmt` customize options
were not included under the `sql` group. It was not possible to control if
`sqlfmt` reused an existing error buffer or generated new ones.

- Added `sqlfmt-region` interactive command and binding under `sql-mode` keymap
  - `sqlfmt-buffer` calls into `sqlfmt-region` with `(point-min)` and
    `(point-max`)

- Added `sqlfmt` customize group as child to `sql` customize group

- Added `sqlfmt-reuse-error-buffer` option

- Updated `sql` layer documentation to reflect changes

CHANGELOG.develop

@@ -3095,6 +3095,8 @@ Other:
 - Added key binding (thanks to Michael Hauser-Raspe):
   ~SPC m b c~ connect to a SQLi buffer from your saved buffer list
 - Added ~SPC m g~ prefix: =goto= (thanks to duianto)
+- Added regional ~sqlfmt~ invocation, error handling, and formatting bindings
+  (thanks to 0x6362)
 **** Spell-checking
 - Added spell checking transient state (thanks to Francesc Elies Henar)
 - Update to flyspell-correct v0.5 (thanks to Boris Buliga)

layers/+lang/sql/README.org

@@ -8,6 +8,7 @@
 - [[#description][Description]]
   - [[#features][Features:]]
 - [[#install][Install]]
+  - [[#external-dependencies][External Dependencies:]]
   - [[#sql-keywords-capitalization][SQL Keywords Capitalization]]
     - [[#sql-interactive-mode][SQL Interactive Mode]]
     - [[#blacklisting-keywords][Blacklisting keywords]]
@@ -39,7 +40,7 @@ This layer adds support for a wide range of SQL dialects to Spacemacs.
   - Sybase
   - Vertica
 - Syntax-checking via [[https://github.com/purcell/sqlint][sqlint]] for ANSI SQL.
-- Format code with =sqlfmt=
+- Format code with [[https://github.com/mjibson/sqlfmt][=sqlfmt=]]
 - Snippet insertion for the more general SQL constructs.
 - REPL support via =SQLi= buffer.
 - Automatic capitalization of keywords.
@@ -49,7 +50,10 @@ To use this configuration layer, add it to your =~/.spacemacs=. You will need to
 add =sql= to the existing =dotspacemacs-configuration-layers= list in this
 file.
 
-For syntax-checking you also need to install [[https://www.ruby-lang.org/en/about/][ruby]] as well as =sqlint=.
+** External Dependencies:
+   Some functionality, like linting, rely on external binaries:
+   - *Syntax Checking*: Install [[https://www.ruby-lang.org/en/about/][ruby]] and the =sqlint= gem.
+   - *Formatting*: Install [[https://github.com/mjibson/sqlfmt][sqlfmt]] and move it into your =$PATH=
 
 #+BEGIN_SRC ruby
   gem install sqlint
@@ -140,4 +144,8 @@ auto-indent by setting the variable =sql-auto-indent= to =nil=.
 
 ** Code Formatting
 
-| ~SPC m = c~ | capitalize SQL keywords in region (if capitalize is enabled) |
+| Key binding  | Description                                                  |
+|--------------+--------------------------------------------------------------|
+| ~SPC m = c~  | capitalize SQL keywords in region (if capitalize is enabled) |
+| ~SPC m = ==~ | ~sqlfmt~ whole buffer                                        |
+| ~SPC m = r=~ | ~sqlfmt~ active region                                       |

layers/+lang/sql/local/sqlfmt/sqlfmt.el

@@ -1,3 +1,7 @@
+(defgroup sqlfmt nil
+  "Easy sqlfmt invocation in Emacs"
+  :group 'sql)
+
 (defcustom sqlfmt-executable
   "sqlfmt"
   "Location of sqlfmt executable."
@@ -8,21 +12,43 @@
   "Command line options to pass to sqlfmt."
   :type '(repeat string))
 
+(defcustom sqlfmt-reuse-error-buffer
+  nil
+  "Reuse the same buffer for sqlfmt errors, replacing content on new invocations, or generate new buffers on each invocation"
+  :type 'boolean)
+
 (defun sqlfmt-buffer ()
   (interactive)
-  (let* ((orig-buffer (current-buffer))
+  (sqlfmt-region (point-min) (point-max)))
+
+(defun sqlfmt-region (start end)
+  "Calls sqlfmt on region"
+  (interactive (if (use-region-p)
+                   (list (region-beginning) (region-end))
+                 (list nil nil)))
+  (if (not (and start end))
+      (error "No region active, sqlfmt cancelled"))
+  (let* ((sqlfmt-buffer-base "*sqlfmt*")
+         (inhibit-read-only t)
+         (orig-buffer (current-buffer))
          (orig-point (point))
-         (tmpbuf (generate-new-buffer "*sqlfmt*"))
-         (status-code (apply #'call-process-region (point-min) (point-max)
-                             sqlfmt-executable nil tmpbuf nil
-                             sqlfmt-options)))
+         (tmpbuf (if sqlfmt-reuse-error-buffer
+                     (get-buffer-create sqlfmt-buffer-base)
+                   (generate-new-buffer sqlfmt-buffer-base)))
+         (status-code (progn
+                        (with-current-buffer tmpbuf
+                          (erase-buffer)
+                          (setq buffer-read-only t))
+                        (apply #'call-process-region start end
+                              sqlfmt-executable nil tmpbuf nil
+                              sqlfmt-options))))
     (deactivate-mark)
-    (with-current-buffer tmpbuf
-      (setq buffer-read-only t))
     (if (eq status-code 0)
         (progn
-          (with-current-buffer tmpbuf
-            (copy-to-buffer orig-buffer (point-min) (point-max)))
-          (kill-buffer tmpbuf)
-          (goto-char orig-point))
+          (with-current-buffer orig-buffer
+           (delete-region start end)
+           (insert-buffer tmpbuf)
+           (kill-buffer tmpbuf)
+           (goto-char orig-point))
+          (message "sqlfmt applied"))
       (error "sqlfmt failed, see %s buffer for details." (buffer-name tmpbuf)))))

layers/+lang/sql/packages.el

@@ -185,8 +185,11 @@
   (use-package sqlfmt
     :commands sqlfmt-buffer
     :init
-    (spacemacs/set-leader-keys-for-major-mode 'sql-mode
-      "=" 'sqlfmt-buffer)))
+    (progn
+      (spacemacs/declare-prefix-for-mode 'sql-mode "mf" "formatting")
+      (spacemacs/set-leader-keys-for-major-mode 'sql-mode
+        "=r" 'sqlfmt-region
+        "==" 'sqlfmt-buffer))))
 
 (defun sql/init-sqlup-mode ()
   (use-package sqlup-mode