Allow nil results

Author: fbiville

neo4j/session.go

@@ -259,7 +259,7 @@ func (s *session) runRetriable(
 		DatabaseName:            s.databaseName,
 	}
 	for state.Continue() {
-		if workResult := s.tryRun(&state, mode, &config, work); workResult != nil {
+		if workResult, successfullyCompleted := s.tryRun(&state, mode, &config, work); successfullyCompleted {
 			return workResult, nil
 		}
 	}
@@ -292,12 +292,12 @@ func (s *session) WriteTransaction(
 	return s.runRetriable(db.WriteMode, work, configurers...)
 }
 
-func (s *session) tryRun(state *retry.State, mode db.AccessMode, config *TransactionConfig, work TransactionWork) interface{} {
+func (s *session) tryRun(state *retry.State, mode db.AccessMode, config *TransactionConfig, work TransactionWork) (interface{}, bool) {
 	// Establish new connection
 	conn, err := s.getConnection(mode)
 	if err != nil {
 		state.OnFailure(conn, err, false)
-		return nil
+		return nil, false
 	}
 	defer s.pool.Return(conn)
 	txHandle, err := conn.TxBegin(db.TxConfig{
@@ -308,7 +308,7 @@ func (s *session) tryRun(state *retry.State, mode db.AccessMode, config *Transac
 	})
 	if err != nil {
 		state.OnFailure(conn, err, false)
-		return nil
+		return nil, false
 	}
 
 	tx := retryableTransaction{conn: conn, fetchSize: s.fetchSize, txHandle: txHandle}
@@ -321,17 +321,17 @@ func (s *session) tryRun(state *retry.State, mode db.AccessMode, config *Transac
 		// but instead rely on pool invoking reset on the connection, that
 		// will do an implicit rollback.
 		state.OnFailure(conn, err, false)
-		return nil
+		return nil, false
 	}
 
 	err = conn.TxCommit(txHandle)
 	if err != nil {
 		state.OnFailure(conn, err, true)
-		return nil
+		return nil, false
 	}
 
 	s.retrieveBookmarks(conn)
-	return x
+	return x, true
 }
 
 func (s *session) getServers(ctx context.Context, mode db.AccessMode) ([]string, error) {

neo4j/session_test.go

@@ -152,6 +152,22 @@ func TestSession(st *testing.T) {
 			}()
 			_, _ = newSession.WriteTransaction(transactionFunction)
 		})
+
+		rt.Run("tx function panic returns conn to pool and bubbles up", func(t *testing.T) {
+			_, pool, newSession := createSession()
+			pool.BorrowConn = &ConnFake{Alive: true}
+			transactionFunction := func(Transaction) (interface{}, error) {
+				return nil, nil
+			}
+
+			result, err := newSession.WriteTransaction(transactionFunction)
+			if result != nil {
+				t.Errorf("expected nil result")
+			}
+			if err != nil {
+				t.Errorf("expected nil error")
+			}
+		})
 	})
 
 	st.Run("Bookmarking", func(bt *testing.T) {