Allow a formatter rule to override the executable name

format-all.el

@@ -273,7 +273,11 @@ language. Each formatter is either:
 * a symbol (e.g. black, clang-format, rufo)
 
 * a list whose first item is that symbol, and any remaining items
-  are extra command line arguments to pass to the formatter
+  are extra command line arguments to pass to the formatter; if
+  it starts with the symbol `:executable' the following item is
+  the program name that overrides EXECUTABLE and can be a
+  relative path from the project root, and the rest items are its
+  arguments.  Those arguments should not be shell-quoted.
 
 If more than one formatter is given for the same language, all of
 them are run as a chain, with the code from each formatter passed
@@ -305,7 +309,9 @@ the rules for an entire source tree can be given in one file.")
       (error "Formatter name missing"))
     (unless (symbolp (car formatter))
       (error "Formatter name is not a symbol: %S" (car formatter)))
-    (unless (cl-every #'stringp (cdr formatter))
+    (unless (or (and (eq (cadr formatter) :executable)
+                     (cl-every #'stringp (cddr formatter)))
+                (cl-every #'stringp (cdr formatter)))
       (error "Formatter command line arguments are not all strings: %S"
              formatter))
     formatter))
@@ -326,12 +332,9 @@ the rules for an entire source tree can be given in one file.")
                (stringp (car chain))
                (cl-every
                 (lambda (formatter)
-                  (and (not (null formatter))
-                       (or (symbolp formatter)
-                           (and (format-all--proper-list-p formatter)
-                                (and (symbolp (car formatter))
-                                     (not (null (car formatter))))
-                                (cl-every #'stringp (cdr formatter))))))
+                  (condition-case nil
+                      (format-all--normalize-formatter formatter)
+                    (error nil)))
                 (cdr chain))))
         formatters)))
 
@@ -482,8 +485,11 @@ OK-STATUSES.  OK-STATUSES and ERROR-REGEXP are hacks to work
 around formatter programs that don't make sensible use of their
 exit status.
 
-If ARGS are given, those are arguments to EXECUTABLE. They should
-not be shell-quoted.
+If ARGS are given, those are arguments to EXECUTABLE.  If it
+starts with the symbol `:executable' the following item is the
+program name that overrides EXECUTABLE and can be a relative path
+from the project root, and the rest items are its arguments.
+Those arguments should not be shell-quoted.
 
 If ROOT-FILES are given, the working directory of the formatter
 will be the deepest directory (starting from the file being
@@ -522,8 +528,11 @@ unformatted code from stdin, write its formatted equivalent to
 stdout, write errors/warnings to stderr, and exit zero/non-zero
 on success/failure.
 
-If ARGS are given, those are arguments to EXECUTABLE.  They don't
-need to be shell-quoted."
+If ARGS are given, those are arguments to EXECUTABLE.  If it
+starts with the symbol `:executable' the following item is the
+program name that overrides EXECUTABLE and can be a relative path
+from the project root, and the rest items are its arguments.
+Those arguments should not be shell-quoted."
   (apply 'format-all--buffer-hard nil nil nil executable args))
 
 (defun format-all--ruby-gem-bundled-p (gem-name)
@@ -1578,6 +1587,31 @@ STATUS and ERROR-OUTPUT come from the formatter."
     (set-marker (mark-marker) old-mark (current-buffer))
     (setq mark-ring (mapcar #'copy-marker old-mark-ring))))
 
+(defun format-all--project-root ()
+  "Internal function to get the project root for the current buffer."
+  (or (and (fboundp 'projectile-project-root)
+           (ignore-errors (projectile-project-root)))
+      (ignore-errors (project-root (project-current)))
+      default-directory))
+
+(defun format-all--command-args (formatter)
+  "Internal function to get the full command line arguments for FORMATTER."
+  (let* ((name (car formatter))
+         (args (cdr formatter)))
+    (if (eq (car args) :executable)
+        (let* ((executable (cadr args))
+               (args (cddr args))
+               (executable
+                (or (let ((project-executable (expand-file-name executable (format-all--project-root))))
+                      (and (file-executable-p project-executable)
+                           (file-regular-p project-executable)
+                           project-executable))
+                    (executable-find executable)
+                    (signal 'format-all-executable-not-found
+                            (list (format "You need the %s command." executable))))))
+          (cons executable args))
+      (cons (format-all--formatter-executable name) args))))
+
 (defun format-all--run-chain (language chain region)
   "Internal function to run a formatter CHAIN on the current buffer.
 
@@ -1608,9 +1642,10 @@ entire buffer."
              (cl-return))
            (let* ((formatter (car chain-tail))
                   (f-name (car formatter))
-                  (f-args (cdr formatter))
-                  (f-function (gethash f-name format-all--format-table))
-                  (f-executable (format-all--formatter-executable f-name)))
+                  (f-command-args (format-all--command-args formatter))
+                  (f-executable (car f-command-args))
+                  (f-args (cdr f-command-args))
+                  (f-function (gethash f-name format-all--format-table)))
              (when format-all-debug
                (message
                 "Format-All: Formatting %s as %s using %S%s"