Diff dbs with different types of the same attribute (closes #369)

Author: darkleaf

src/datascript/db.cljc

@@ -422,11 +422,15 @@
       :else
       (let [first-a (first a)
             first-b (first b)
-            diff (cmp first-a first-b)]
+            diff (try
+                   (cmp first-a first-b)
+                   (catch #?(:clj ClassCastException :cljs js/Error) _
+                     :incomparable))]
         (cond
-          (== diff 0) (recur only-a                only-b                (conj both first-a) (next a) (next b))
-          (< diff 0)  (recur (conj only-a first-a) only-b                both                (next a) b)
-          (> diff 0)  (recur only-a                (conj only-b first-b) both                a        (next b)))))))
+          (= diff :incomparable) (recur (conj only-a first-a) (conj only-b first-b) both                (next a) (next b))
+          (== diff 0)            (recur only-a                only-b                (conj both first-a) (next a) (next b))
+          (< diff 0)             (recur (conj only-a first-a) only-b                both                (next a) b)
+          (> diff 0)             (recur only-a                (conj only-b first-b) both                a        (next b)))))))
 
 ;; ----------------------------------------------------------------------------
 

test/datascript/test/issues.cljc

@@ -34,3 +34,12 @@
            filtered (ds/filter base (constantly true))]
        (t/is (= (with-out-str (clojure.pprint/pprint base))
                 (with-out-str (clojure.pprint/pprint filtered)))))))
+
+(deftest ^{:doc "Can't diff databases with different types of the same attribute"}
+  issue-369
+  (let [db1 (-> (ds/empty-db)
+                (ds/db-with [[:db/add 1 :attr :aa]]))
+        db2 (-> (ds/empty-db)
+                (ds/db-with [[:db/add 1 :attr "aa"]]))]
+    (t/is (= [[(ds/datom 1 :attr :aa)] [(ds/datom 1 :attr "aa")] nil]
+             (clojure.data/diff db1 db2)))))