From 93058611026b5ce420ae641c04f662cc9afc0afe Mon Sep 17 00:00:00 2001
From: Matthias Koefferlein <matthias@koefferlein.de>
Date: Tue, 1 Dec 2020 23:00:11 +0100
Subject: [PATCH] Bugfix (consider porting): undo triggered

Transaction::cancel was sometimes triggering an undo:
when the current transaction was empty, "commit" did just
remove it which made the subsequent undo act on the
*previous* transaction.
---
 src/db/db/dbManager.cc | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/src/db/db/dbManager.cc b/src/db/db/dbManager.cc
index 405c0f45b..5e53b1a83 100644
--- a/src/db/db/dbManager.cc
+++ b/src/db/db/dbManager.cc
@@ -147,15 +147,24 @@ Manager::last_transaction_id () const
 void
 Manager::cancel ()
 {
+  //  equivalent to commit and undo. But takes care that an empty commit is not followed by undo
+  //  (which would undo the previous transaction!)
   if (m_enabled) {
 
-    //  commit and undo - revert changes done so far
-    commit ();
-    undo ();
+    tl_assert (m_opened);
+    tl_assert (! m_replay);
+    m_opened = false;
 
-    //  delete all following transactions
-    erase_transactions (m_current, m_transactions.end ());
-    m_current = m_transactions.end ();
+    if (m_current->first.begin () != m_current->first.end ()) {
+
+      ++m_current;
+      undo ();
+
+    } else {
+      //  empty transactions .. just delete
+      erase_transactions (m_current, m_transactions.end ());
+      m_current = m_transactions.end ();
+    }
 
   }
 }