fix purcell#25 hook for post-processing formatter output

reformatter.el

@@ -83,14 +83,15 @@ otherwise as it cannot create intermediate directories."
   (make-temp-file
    (replace-regexp-in-string "/" "_" (symbol-name sym))))
 
-(defun reformatter--do-region (name beg end program args stdin stdout input-file exit-code-success-p display-errors)
+(defun reformatter--do-region (name beg end program args stdin stdout input-file exit-code-success-p output-processor 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."
   (cl-assert input-file)
   (cl-assert (functionp exit-code-success-p))
+  (cl-assert (or (null output-processor) (functionp exit-code-success-p)))
   (when (and input-file
              (buffer-file-name)
              (string= (file-truename input-file)
@@ -130,9 +131,19 @@ the `reformatter-define' macro."
                     ;; 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* ((output-file (if stdout stdout-file input-file))
+                           result-file
+                           (result-callback (lambda (output)
+                                              (setq result-file
+                                                    (and output
+                                                         (reformatter-temp-file-in-current-directory nil output))))))
+                      (if (functionp output-processor)
+                          (progn
+                            (funcall output-processor output-file result-callback)
+                            (when result-file
+                              (reformatter-replace-buffer-contents-from-file result-file)
+                              (delete-file result-file)))
+                        (reformatter-replace-buffer-contents-from-file output-file))))
                   ;; If there are no errors then we hide the error buffer
                   (delete-windows-on error-buffer))
               (if display-errors
@@ -142,7 +153,7 @@ 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-processor)
   "Define a reformatter command with NAME.
 
 When called, the reformatter will use PROGRAM and any ARGS to
@@ -234,10 +245,17 @@ EXIT-CODE-SUCCESS-P
   which accepts an integer process exit code, and returns non-nil
   if that exit code is considered successful.  This could be a
   lambda, quoted symbol or sharp-quoted symbol.  If not supplied,
-  the code is considered successful if it is `zerop'."
-  (declare (indent defun))
+  the code is considered successful if it is `zerop'.
+
+OUTPUT-PROCESSOR
+
+  If provided, this is a function that takes the output PROGRAM,
+  do some arbitrary processing to it, and then return the final
+  output.  If not supplied, the output is returned as is."
+  (declare (indent defun) (debug (name :program :args :mode :stdin :stdout :input-file :lighter :keymap :group :exit-code-success-p :output-processor)))
   (cl-assert (symbolp name))
   (cl-assert (functionp exit-code-success-p))
+  (cl-assert (or (null output-processor) (functionp exit-code-success-p)))
   (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.
@@ -285,7 +303,7 @@ 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-processor display-errors))
              (when (file-exists-p input-file)
                (delete-file input-file)))))