From b20c70fc2a6c7a747e645bd6c4e87ee659e23047 Mon Sep 17 00:00:00 2001
From: Nick Alexander <nalexander@mozilla.com>
Date: Thu, 13 Oct 2016 12:23:25 -0700
Subject: [PATCH] Review comment: ensure report is non-nil after
 in-transaction!.

---
 src/common/datomish/transact.cljc | 12 ++++++++----
 test/datomish/transact_test.cljc  | 12 ++++++++++++
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/src/common/datomish/transact.cljc b/src/common/datomish/transact.cljc
index bc62ff05..68da51dc 100644
--- a/src/common/datomish/transact.cljc
+++ b/src/common/datomish/transact.cljc
@@ -586,7 +586,7 @@
     (go
       (>! token-chan (gensym "transactor-token"))
       (loop []
-        (let [token (<! token-chan)]
+        (when-let [token (<! token-chan)]
           (when-let [[tx-data result close?] (<! (:transact-chan conn))]
             (let [pair
                   (<! (go-pair ;; Catch exceptions, return the pair.
@@ -594,10 +594,14 @@
                               report (<? (db/in-transaction!
                                            db
                                            #(-> (<with db tx-data))))]
-                          ;; We only get here if the transaction is committed.
-                          (reset! (:current-db conn) (:db-after report))
-                          (>! (:listener-source conn) report)
+                          (when report
+                            ;; <with returns non-nil or throws, but we still check report just in
+                            ;; case.  Here, in-transaction! function completed and returned non-nil,
+                            ;; so the transaction has committed.
+                            (reset! (:current-db conn) (:db-after report))
+                            (>! (:listener-source conn) report))
                           report)))]
+              ;; Even when report is nil (transaction not committed), pair is non-nil.
               (>! result pair))
             (>! token-chan token)
             (when close?
diff --git a/test/datomish/transact_test.cljc b/test/datomish/transact_test.cljc
index 1436eea9..34970f8b 100644
--- a/test/datomish/transact_test.cljc
+++ b/test/datomish/transact_test.cljc
@@ -209,4 +209,16 @@
                (tempids r)))
         (is (= nil (a/poll! lc)))))))
 
+(deftest-db test-failing-transacts conn
+  (let [{tx0 :tx} (<? (d/<transact! conn test-schema))]
+    (testing "failing transact throws"
+      (is (thrown-with-msg?
+            ExceptionInfo #"expected :db.type/string"
+            (<? (d/<transact! conn [{:db/id (d/id-literal :db.part/user -1) :name 1}])))))
+
+    (testing "transaction after bad transaction is applied"
+      (<? (d/<transact! conn [{:db/id 101 :name "Petr"}]))
+      (is (= (<? (<datoms-after (d/db conn) tx0))
+             #{[101 :name "Petr"]})))))
+
 #_ (time (t/run-tests))