Defer evaluation of custom-set-faces!'s arguments

...until the theme has first loaded.

You'll need to set `doom-theme` to nil if you want to use this macro
without a theme!

core/autoload/themes.el

@@ -10,31 +10,34 @@
         (`((,(car spec) ,(cdr spec))))))
 
 ;;;###autoload
-(defun custom-theme-set-faces! (theme &rest specs)
+(defmacro custom-theme-set-faces! (theme &rest specs)
   "Apply a list of face SPECS as user customizations for THEME.
 
 THEME can be a single symbol or list thereof. If nil, apply these settings to
 all themes. It will apply to all themes once they are loaded."
-  (let* ((themes (doom-enlist (or theme 'user)))
+  (declare (indent defun))
+  `(let* ((themes (doom-enlist (or (list ,theme) 'user)))
           (fn (gensym (format "doom--customize-%s-h-" (mapconcat #'symbol-name themes "-")))))
-    (fset fn
-          (lambda ()
+     (fset
+      fn (lambda ()
            (dolist (theme themes)
              (when (or (eq theme 'user)
                        (custom-theme-enabled-p theme))
                (apply #'custom-theme-set-faces 'user
                       (mapcan #'doom--custom-theme-set-face
-                               specs))))))
-    (funcall fn)
-    (add-hook 'doom-load-theme-hook fn)))
+                              (list ,@specs)))))))
+     (when (or doom-init-theme-p (null doom-theme))
+       (funcall fn))
+     (add-hook 'doom-load-theme-hook fn 'append)))
 
 ;;;###autoload
-(defun custom-set-faces! (&rest specs)
+(defmacro custom-set-faces! (&rest specs)
   "Apply a list of face SPECS as user customizations.
 
 This is a drop-in replacement for `custom-set-face' that allows for a simplified
 face format."
-  (apply #'custom-theme-set-faces! 'user specs))
+  (declare (indent defun))
+  `(custom-theme-set-faces! 'user ,@specs))
 
 (defvar doom--prefer-theme-elc)
 ;;;###autoload

core/core-ui.el

@@ -3,6 +3,9 @@
 ;;
 ;;; Variables
 
+(defvar doom-init-theme-p nil
+  "If non-nil, a theme as been loaded.")
+
 (defvar doom-theme nil
   "A symbol representing the Emacs theme to load at startup.
 
@@ -633,7 +636,8 @@ behavior). Do not set this directly, this is let-bound in `doom-init-theme-h'.")
   "Set up `doom-load-theme-hook' to run after `load-theme' is called."
   :after-while #'load-theme
   (unless no-enable
-    (setq doom-theme theme)
+    (setq doom-theme theme
+          doom-init-theme-p t)
     (run-hooks 'doom-load-theme-hook)))
 
 (defadvice! doom--prefer-compiled-theme-a (orig-fn &rest args)