Clang: Handle a busy database in the PCH plugin

This can be always happen for write statements. It fixes the wrong behavior
of the transaction that it tried to rollback if begin fails. If begin fails
the transaction never started so there is nothing to rollback.

Change-Id: I8a03162257fa22a0bb66ccb844f90c6afbc7db64
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/libs/sqlite/sqlitetransaction.h

@@ -71,9 +71,11 @@ protected:
     {
     }
 
+
 protected:
     TransactionInterface &m_interface;
     bool m_isAlreadyCommited = false;
+    bool m_rollback = false;
 };
 
 class AbstractThrowingTransaction : public AbstractTransaction
@@ -84,7 +86,7 @@ public:
     ~AbstractThrowingTransaction() noexcept(false)
     {
         try {
-            if (!m_isAlreadyCommited)
+            if (m_rollback)
                 m_interface.rollback();
         } catch (...) {
             if (!std::uncaught_exception())
@@ -107,7 +109,7 @@ public:
     ~AbstractNonThrowingDestructorTransaction()
     {
         try {
-            if (!m_isAlreadyCommited)
+            if (m_rollback)
                 m_interface.rollback();
         } catch (...) {
         }
@@ -129,6 +131,11 @@ public:
     {
         interface.deferredBegin();
     }
+
+    ~BasicDeferredTransaction()
+    {
+        BaseTransaction::m_rollback = !BaseTransaction::m_isAlreadyCommited;
+    }
 };
 
 using DeferredTransaction = BasicDeferredTransaction<AbstractThrowingTransaction>;
@@ -143,6 +150,11 @@ public:
     {
         interface.immediateBegin();
     }
+
+    ~BasicImmediateTransaction()
+    {
+        BaseTransaction::m_rollback = !BaseTransaction::m_isAlreadyCommited;
+    }
 };
 
 using ImmediateTransaction = BasicImmediateTransaction<AbstractThrowingTransaction>;
@@ -157,6 +169,11 @@ public:
     {
         interface.exclusiveBegin();
     }
+
+    ~BasicExclusiveTransaction()
+    {
+        BaseTransaction::m_rollback = !BaseTransaction::m_isAlreadyCommited;
+    }
 };
 
 using ExclusiveTransaction = BasicExclusiveTransaction<AbstractThrowingTransaction>;