Warn if layers changed outside dotspacemacs/layers

core/core-configuration-layer.el

@@ -375,6 +375,8 @@ refreshed during the current session."
   "Synchronize declared layers in dotfile with spacemacs.
 If NO-INSTALL is non nil then install steps are skipped."
   (dotspacemacs|call-func dotspacemacs/layers "Calling dotfile layers...")
+  (setq dotspacemacs--configuration-layers-saved
+        dotspacemacs-configuration-layers)
   (when (spacemacs-buffer//choose-banner)
     (spacemacs-buffer//inject-version))
   ;; declare used layers then packages as soon as possible to resolve

core/core-dotspacemacs.el

@@ -126,6 +126,9 @@ whenever you start Emacs.")
 (defvar dotspacemacs-configuration-layers '(emacs-lisp)
   "List of configuration layers to load.")
 
+(defvar dotspacemacs--configuration-layers-saved nil
+  "Saved value of `dotspacemacs-configuration-layers' after sync.")
+
 (defvar dotspacemacs-themes '(spacemacs-dark
                               spacemacs-light)
   "List of themes, the first of the list is loaded when spacemacs starts.
@@ -362,6 +365,16 @@ are caught and signalled to user in spacemacs buffer."
                                            (error-message-string err))
                                    t))))))
 
+(defun dotspacemacs//check-layers-changed ()
+  "Check if the value of `dotspacemacs-configuration-layers'
+changed, and issue a warning if it did."
+  (unless (eq dotspacemacs-configuration-layers
+              dotspacemacs--configuration-layers-saved)
+    (spacemacs-buffer/warning
+     "`dotspacemacs-configuration-layers' was changed outside of `dotspacemacs/layers'.")))
+(add-hook 'spacemacs-post-user-config-hook
+          'dotspacemacs//check-layers-changed)
+
 (defun dotspacemacs//read-editing-style-config (config)
   "Read editing style CONFIG: apply variables and return the editing style.
 CONFIG can be the symbol of an editing style or a list where the car is

core/core-spacemacs.el

@@ -225,7 +225,7 @@ defer call using `spacemacs-post-user-config-hook'."
          ((configuration-layer/layer-usedp 'ivy)
           'ivy)
          (t 'helm))
-   (pp-to-string dotspacemacs-configuration-layers)
+   (pp-to-string dotspacemacs--configuration-layers-saved)
    (bound-and-true-p system-configuration-features)))
 
 (defun spacemacs/describe-system-info ()