Add an alternative Ring session store that uses Clojure reader serialization

This way libraries like Friend, that use namespaced keywords (::identity) and other
Clojure-specific data structures will work well with Monger.

Current store will strip off namespace information from namespaced keywords
because clojure.core/name work that way. For example: (name ::identity).

Reported by Julio Barros.

src/clojure/monger/ring/session_store.clj

@@ -18,6 +18,49 @@
 ;; API
 ;;
 
+;; this session store stores Clojure data structures using Clojure reader. It will correctly store every
+;; data structure Clojure reader can serialize and read but won't make the data useful to applications
+;; in other languages.
+
+(defrecord ClojureReaderBasedMongoDBSessionStore [^String collection-name])
+
+(extend-protocol ringstore/SessionStore
+  ClojureReaderBasedMongoDBSessionStore
+
+  (read-session [store key]
+    #_ (if-let [m (and key
+                       (mc/find-one-as-map (.collection-name store) {:_id key}))]
+         m
+         {})
+    (if key
+      (if-let [m (mc/find-one-as-map (.collection-name store) {:_id key})]
+        (read-string (:value m))
+        {})
+      {}))
+
+  (write-session [store key data]
+    (let [date  (Date.)
+          key   (or key (str (UUID/randomUUID)))
+          value (binding [*print-dup* true]
+                  (pr-str (assoc data :date date :_id key)))]
+      (mc/save (.collection-name store) {:_id key :date date :value value})
+      key))
+
+  (delete-session [store key]
+    (mc/remove-by-id (.collection-name store) key)
+    nil))
+
+
+(defn session-store
+  ([]
+     (ClojureReaderBasedMongoDBSessionStore. default-session-store-collection))
+  ([^String s]
+     (ClojureReaderBasedMongoDBSessionStore. s)))
+
+
+;; this session store won't store namespaced keywords correctly but stores results in a way
+;; that applications in other languages can read. DO NOT use it with Friend.
+
 (defrecord MongoDBSessionStore [^String collection-name])
 
 (extend-protocol ringstore/SessionStore

test/monger/test/ring/clojure_session_store_test.clj

@@ -0,0 +1,54 @@
+(ns monger.test.ring.session-store-test
+  (:require [monger core util]
+            [monger.collection  :as mc]
+            [monger.test.helper :as helper])  
+  (:use clojure.test
+        ring.middleware.session.store
+        monger.ring.session-store))
+
+
+(helper/connect!)
+
+(defn purge-sessions
+  [f]
+  (mc/remove "web_sessions")
+  (mc/remove "sessions")
+  (f)
+  (mc/remove "web_sessions")
+  (mc/remove "sessions"))
+
+(use-fixtures :each purge-sessions)
+
+
+(deftest test-reading-a-session-that-does-not-exist
+  (let [store (session-store)]
+    (is (= {} (read-session store "a-missing-key-1228277")))))
+
+
+(deftest test-reading-a-session-that-does-exist
+  (let [store (session-store)
+        sk    (write-session store nil {:library "Monger"})
+        m     (read-session store sk)]
+    (is sk)
+    (is (and (:_id m) (:date m)))
+    (is (= (dissoc m :_id :date)
+           {:library "Monger"}))))
+
+
+(deftest test-updating-a-session
+  (let [store (session-store "sessions")
+        sk1   (write-session store nil {:library "Monger"})
+        sk2   (write-session store sk1 {:library "Ring"})
+        m     (read-session store sk2)]
+    (is (and sk1 sk2))
+    (is (and (:_id m) (:date m)))
+    (is (= sk1 sk2))
+    (is (= (dissoc m :_id :date)
+           {:library "Ring"}))))
+
+
+(deftest test-deleting-a-session
+  (let [store (session-store "sessions")
+        sk    (write-session store nil {:library "Monger"})]
+    (is (nil? (delete-session store sk)))
+    (is (= {} (read-session store sk)))))