Chapter 11 commit (Errors/Exceptions).

This was hard to follow because the translation was quite bad. The
gist of was use 'throw-code' for quick and basic relay of error (using
HTTP response codes) and use 'on-exception' method to generate a more
involved HTML page to communicate the error (HTTP response code). At
least, I think that was the take-away.

src/web.lisp

@@ -27,7 +27,6 @@
 
 ;;
 ;; Routing rules
-
 (defroute "/" ()
   "Top page"
   (let ((articless (articles-make 5)))
@@ -38,7 +37,7 @@
                              ,@(roles)
                              :token ,(token)
                              :alert ,(flash-gethash :alert ningle:*session*)
-                             ;; :news ,articles
+                             :news ,articless
                              :blogs (1 2 3 4 5)
                              :articles ,articless))))
 
@@ -1166,3 +1165,84 @@ nil "/users/~D"(mito:object-id user))))))))
 				     (:or (:= "public" :status)
 					  (:= "member-only" :status)))))))
       (sxql:order-by (:desc :date-posted)) (when limit (sxql:limit limit)))))
+
+;;; -------------------------------------------------------------------------
+;;; Custom Error Pages
+
+;;; 'throw-code' seems to be the most convenient way to generate an
+;;; error page. But, it does not lend itself to generating a more
+;;; involved error page like the 'on-exception' defmethod's do.
+
+;;; (throw-code 405 :allow "put get" :method "post"))
+
+(defroute "/error-test" ()
+  ;; Change the error code (I.E. 405) to test different errors.
+   (throw-code 405 :allow "put get" :method "post"))
+  
+
+(defmethod on-exception ((app <web>) (code method-not-allowed))
+  (setf (getf (lack.response:response-headers ningle:*response*):allow)
+	(allow code))
+  (format nil "Unknown method ~S" (not-allowed code)))
+
+(defmethod on-exception ((app <web>) (code method-not-allowed))
+  `(,(caveman2.exception:exception-code code)
+    (:allow ,(allow code))
+    (,(format nil "Unknown method ~S" (not-allowed code)))))
+
+;;; The original 'on-exception' 404 error is higher up this file.
+(defmethod on-exception ((app <web>) (code (eql 404)))
+  (declare (ignore app))
+  (render "_errors/not-found.html")) ; You can adjust the '404 page'.
+
+;;; Here is a commented-out copy of it for quick reference.
+;; (defmethod on-exception ((app <web>) (code (eql 404)))
+;;   (declare (ignore app))
+;;   (merge-pathnames #P"_errors/404.html"
+;;                    *template-directory*))
+
+#| I DO NOT KNOW WHAT 'STATUS-CODE:+BAD-REQUEST+' IS REFERRING TO
+======================================================================
+
+This method is taken directly from Chapter 11. The 'status-code' part
+is not recognised which means I cannot compile the program (or use
+quickload). Because of this I have commented it out so I can keep it
+as a reference and hopefully work out where '+bad-request+' resides so
+I can import it and get this piece of code working.
+
+(defmethod on-exception ((app <web>)
+			 (code (eql status-code:+bad-request+)))
+  (declare (ignore app))
+  (render "errors/bad-request.html"
+	  `(:alert ,(flash-gethash :alert ningle:*session*))))
+|#
+
+#| Added in Chapter 11 (Errors)
+======================================================================
+Below, I think, is examples of how to form more complicated error
+messages/pages/exceptions beyond what is provided by Caveman. I cannot
+say for certain because the chapter's text is a bit hard to
+read (Chapter 11). Google's Japanese to English translation is the
+worse of all the chapters I have read up to now.
+|#
+(define-condition method-not-allowed (caveman2.exception:http-exception)
+  ((allow
+    :initarg :allow
+    :reader allow)
+   (method
+    :initarg :method
+    :reader not-allowed)))
+
+;;; --------------------------------------------------------------------
+;;; Code examples for using 'define-condition' above.
+;;; These code snippets are taken directly from Chapter 11.
+
+#|
+(let ((caveman2.exception:*exception-class*
+	'method-not-allowed))
+  (throw-code 405 :allow "put get" :method "post"))
+
+(error 'method-not-allowed :method "post" :allow "put get" :code 405)
+
+`(405 (:allow "put get")(,(format nil "Unknown method ~S""post")))
+|#

templates/_errors/bad-request.html

@@ -0,0 +1,9 @@
+{% extends "layouts/error.html" %}
+{% block title %}{% lisp (title! "Bad Request") %}{% endblock %}
+
+{% block main %}
+<h1>400 {% lisp (title!) %}</h1>
+{% if alert %}
+<p class="notice">{{alert}}</p>
+{% endif %}
+{% endblock %}

templates/_errors/not-found.html

@@ -0,0 +1,7 @@
+{% extends "layouts/error.html" %}
+
+{% block title %} {% lisp (title! "Not Found") %} {% endblock %}
+
+{% block main %}
+<h1>404 Not Found</h1>
+{% endblock %}

templates/layouts/error.html

@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <title>
+      {% block title %}Title{% endblock %}
+    </title>
+    <link rel="stylesheet" media="all" href="/css/app.css">
+  </head>
+  <body>
+    <div id="container">
+      <header>
+        <img src="/images/lisplogo.svg" alt="Image alt text" width="800" height="400">
+        <nav class="menubar">
+          <a href="/">TOP</a>
+        </nav>
+      </header>
+      <main>
+        {% block main %}Main content here{% endblock %}
+      </main>
+      <footer>
+        {% include "shared/footer.html" %}
+      </footer>
+    </div>
+  </body>
+</html>