Add my own macroexpander

.config.d/99-misc.el

@@ -46,4 +46,42 @@ translation at point."
 (keymap-set mode-specific-map "C-m" margins-map)
 (keymap-set mode-specific-map "b" 'my-insert-buffer-name)
 
+(defun my-preview-macro-expansion (arg)
+  "Previews the expansion of a macro in a temporary window.
+
+If the prefix argument ARG is non-nil, a full recursive
+macroexpansion (`macroexpand-all') will we performed, otherwise only one
+macroexpansion step (`macroexpand-1') will be done.
+
+If there is an active region selected, only its contents will be read
+for the expansion. See also `pp-macroexpand-expression'."
+  (interactive "P")
+  (let ((obj))
+    (if (use-region-p)
+        (setq obj
+                (with-demoted-errors
+                    "Failed to read form: %S"
+                  (read (buffer-substring (region-beginning) (region-end)))))
+      (save-excursion
+        (setq obj (with-demoted-errors
+                    "Failed to read form: %S"
+                  (read (current-buffer))))))
+      (if obj
+          (let ((inhibit-read-only t))
+            (with-current-buffer-window "*Macro Expansion*" nil nil
+              (if arg
+                  (pp (macroexpand-all obj))
+                (pp (macroexpand-1 obj)))
+              (emacs-lisp-mode)
+              (keymap-local-set (kbd "q") #'quit-window))
+            (select-window (get-buffer-window "*Macro Expansion*"))))))
+
+(with-eval-after-load 'embark
+    (setq embark-pre-action-hooks
+          (add-to-list 'embark-pre-action-hooks '(my-preview-macro-expansion embark--beginning-of-target)))
+    (keymap-set embark-expression-map "m" 'my-preview-macro-expansion)
+    (keymap-set embark-expression-map "M" 'pp-macroexpand-expression)
+    (keymap-set embark-defun-map "m" 'my-preview-macro-expansion)
+    (keymap-set embark-defun-map "M" 'pp-macroexpand-expression))
+
 ;;; 99-misc.el ends here