static-pages plugin reports correctly that required fields must be filled in by the user

coleslaw.asd

@@ -21,6 +21,7 @@
   :serial t
   :components ((:file "packages")
                (:file "util")
+	       (:file "errors")
                (:file "config")
                (:file "themes")
                (:file "documents")

plugins/static-pages.lisp

@@ -18,8 +18,13 @@
   ;; default format is markdown (for backward compatibility)
   (:default-initargs :format :md))
 
-(defmethod initialize-instance :after ((object page) &key)
-  (with-slots (coleslaw::url coleslaw::text format) object
+(defmethod initialize-instance :after ((object page) &key url title)
+  (cond
+    ((null url)
+     (error 'coleslaw::required-field-missing :message  (format nil "URL field is missing from static page ~A" (coleslaw::content-file object))))
+    ((null title)
+     (error 'coleslaw::required-field-missing :message (format nil "Title field is missing from static page ~A" (coleslaw::content-file object)))))
+  (with-slots (coleslaw::url coleslaw::text format title) object
     (setf coleslaw::url (make-pathname :defaults coleslaw::url)
           format (alexandria:make-keyword (string-upcase format))
           coleslaw::text (render-text coleslaw::text format))))

src/errors.lisp

@@ -0,0 +1,8 @@
+(in-package :coleslaw)
+
+(define-condition required-field-missing (error)
+  ((message :accessor required-field-missing-message :initarg :message))
+  (:report
+   (lambda (c s)
+     (format s (required-field-missing-message
+	      c)))))