Add OUTPUT-FILTER option

reformatter-tests.el

@@ -68,7 +68,30 @@
  (reformatter-tests-shfmt-in-place)
  (should (equal "[ foo ] && echo yes\n" (buffer-string)))))
 
+(reformatter-define reformatter-tests-output-filter-reverse
+ :program "cat"
+ :output-filter (lambda ()
+ (reverse-region (point-min) (point-max))
+ t)
+ :args nil)
+
+(ert-deftest reformatter-tests-output-filter ()
+ (with-temp-buffer
+ (insert "one\ntwo\n")
+ (reformatter-tests-output-filter-reverse)
+ (should (equal "two\none\n" (buffer-string)))))
+
+(reformatter-define reformatter-tests-output-filter-no-op
+ :program "wc"
+ :output-filter (lambda ()
+ nil)
+ :args nil)
 
+(ert-deftest reformatter-tests-output-filter-no-op ()
+ (with-temp-buffer
+ (insert "one\ntwo\n")
+ (reformatter-tests-output-filter-no-op)
+ (should (equal "one\ntwo\n" (buffer-string)))))
 
 (provide 'reformatter-tests)
 ;;; reformatter-tests.el ends here

reformatter.el

@@ -76,14 +76,28 @@
  (require 'cl-lib))
 (require 'ansi-color)
 
-(defun reformatter--do-region (name beg end program args stdin stdout input-file exit-code-success-p display-errors)
+(defun reformatter--apply-output-filter (program-output-file output-filter)
+ "Run OUTPUT-FILTER in a buffer containing PROGRAM-OUTPUT-FILE.
+The result of OUTPUT-FILTER is returned, and if OUTPUT-FILTER
+succeeded, the buffer's contents will be saved back to
+PROGRAM-OUTPUT-FILE."
+ (with-temp-buffer
+ (insert-file-contents program-output-file)
+ (goto-char (point-min))
+ (let ((success (funcall output-filter)))
+ (when success
+ (write-region (point-min) (point-max) program-output-file nil :quiet))
+ success)))
+
+(defun reformatter--do-region (name beg end program args stdin stdout input-file exit-code-success-p output-filter display-errors)
  "Do the work of reformatter called NAME.
 Reformats the current buffer's region from BEG to END using
 PROGRAM and ARGS. For args STDIN, STDOUT, INPUT-FILE,
-EXIT-CODE-SUCCESS-P and DISPLAY-ERRORS see the documentation of
-the `reformatter-define' macro."
+EXIT-CODE-SUCCESS-P, OUTPUT-FILTER and DISPLAY-ERRORS see the
+documentation of the `reformatter-define' macro."
  (cl-assert input-file)
  (cl-assert (functionp exit-code-success-p))
+ (cl-assert (or (null output-filter) (functionp output-filter)))
  (when (and input-file
  (buffer-file-name)
  (string= (file-truename input-file)
@@ -115,13 +129,14 @@ the `reformatter-define' macro."
  (if (funcall exit-code-success-p retcode)
  (progn
  (save-restriction
- ;; This replacement method minimises
- ;; disruption to marker positions and the
- ;; undo list
- (narrow-to-region beg end)
- (reformatter-replace-buffer-contents-from-file (if stdout
- stdout-file
- input-file)))
+ (let ((replacement-text-file (if stdout stdout-file input-file)))
+ (when (or (null output-filter)
+ (reformatter--apply-output-filter replacement-text-file output-filter))
+ ;; This replacement method minimises
+ ;; disruption to marker positions and the
+ ;; undo list
+ (narrow-to-region beg end)
+ (reformatter-replace-buffer-contents-from-file replacement-text-file))))
  ;; If there are no errors then we hide the error buffer
  (delete-windows-on error-buffer))
  (if display-errors
@@ -131,7 +146,7 @@ the `reformatter-define' macro."
  (delete-file stdout-file))))
 
 ;;;###autoload
-(cl-defmacro reformatter-define (name &key program args (mode t) (stdin t) (stdout t) input-file lighter keymap group (exit-code-success-p 'zerop))
+(cl-defmacro reformatter-define (name &key program args (mode t) (stdin t) (stdout t) input-file lighter keymap group (exit-code-success-p 'zerop) output-filter)
  "Define a reformatter command with NAME.
 
 When called, the reformatter will use PROGRAM and any ARGS to
@@ -191,6 +206,20 @@ INPUT-FILE
  deleted automatically. You might find the function
  `reformatter-temp-file-in-current-directory' helpful.
 
+OUTPUT-FILTER
+
+ Sometimes a reformatter program might output the reformatted
+ text inside structured output such as JSON, so that the
+ structured output would need to be parsed to extract the
+ reformatted text. If provided, OUTPUT-FILTER is expected to be
+ a function with no arguments which will be run in the context
+ of a writeable buffer containing the full output text. The
+ function may then proceed to change the buffer contents so that
+ they contain only the replacement text. If the function
+ returns non-nil, it will be assumed that the output was
+ processed successfully. If the function returns nil, no
+ replacement of the original text will be performed.
+
 MODE
 
  Unless nil, also generate a minor mode that will call the
@@ -226,6 +255,7 @@ EXIT-CODE-SUCCESS-P
  (declare (indent defun))
  (cl-assert (symbolp name))
  (cl-assert (functionp exit-code-success-p))
+ (cl-assert (or (null output-filter) (functionp output-filter)))
  (cl-assert program)
  ;; Note: we skip using `gensym' here because the macro arguments are only
  ;; referred to once below, but this may have to change later.
@@ -271,7 +301,9 @@ DISPLAY-ERRORS, shows a buffer if the formatting fails."
  (reformatter--do-region
  ',name beg end
  ,program ,args ,stdin ,stdout input-file
- #',exit-code-success-p display-errors))
+ #',exit-code-success-p
+ #',output-filter
+ display-errors))
  (when (file-exists-p input-file)
  (delete-file input-file)))))