From 249c8dca20716ef0b20d02dba80b2a185725c4f1 Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Mon, 14 Nov 2016 09:24:06 +1000
Subject: [PATCH] Prioritise provider default literals over reused values when
 creating a new feature

---
 src/core/qgsvectorlayerutils.cpp             | 33 ++++++++------------
 tests/src/python/test_provider_spatialite.py |  8 ++---
 2 files changed, 17 insertions(+), 24 deletions(-)

diff --git a/src/core/qgsvectorlayerutils.cpp b/src/core/qgsvectorlayerutils.cpp
index eb54bfab874..64155b0b04a 100644
--- a/src/core/qgsvectorlayerutils.cpp
+++ b/src/core/qgsvectorlayerutils.cpp
@@ -27,18 +27,6 @@ bool QgsVectorLayerUtils::valueExists( const QgsVectorLayer* layer, int fieldInd
   if ( fieldIndex < 0 || fieldIndex >= fields.count() )
     return false;
 
-  // check - if value is a provider side defaultValueClause then we exclude it from the check
-  if ( fields.fieldOrigin( fieldIndex ) == QgsFields::OriginProvider )
-  {
-    int providerIdx = fields.fieldOriginIndex( fieldIndex );
-    QString providerDefaultClause = layer->dataProvider()->defaultValueClause( providerIdx );
-    if ( !providerDefaultClause.isEmpty() && value.toString() == providerDefaultClause )
-    {
-      // exempt from check
-      return false;
-    }
-  }
-
   QString fieldName = fields.at( fieldIndex ).name();
 
   // build up an optimised feature request
@@ -272,19 +260,24 @@ QgsFeature QgsVectorLayerUtils::createFeature( QgsVectorLayer* layer, const QgsG
       }
     }
 
-    // 3. passed attribute value
-    // note - deliberately not using else if!
-    if ( !v.isValid() && attributes.contains( idx ) )
-    {
-      v = attributes.value( idx );
-    }
-
-    // 4. provider side default literal
+    // 3. provider side default literal
     // note - deliberately not using else if!
     if ( !v.isValid() && fields.fieldOrigin( idx ) == QgsFields::OriginProvider )
     {
       int providerIndex = fields.fieldOriginIndex( idx );
       v = layer->dataProvider()->defaultValue( providerIndex );
+      if ( v.isValid() )
+      {
+        //trust that the provider default has been sensibly set not to violate any constraints
+        checkUnique = false;
+      }
+    }
+
+    // 4. passed attribute value
+    // note - deliberately not using else if!
+    if ( !v.isValid() && attributes.contains( idx ) )
+    {
+      v = attributes.value( idx );
     }
 
     // last of all... check that unique constraints are respected
diff --git a/tests/src/python/test_provider_spatialite.py b/tests/src/python/test_provider_spatialite.py
index 034ea3cf156..e5b722149f8 100644
--- a/tests/src/python/test_provider_spatialite.py
+++ b/tests/src/python/test_provider_spatialite.py
@@ -474,14 +474,14 @@ class TestQgsSpatialiteProvider(unittest.TestCase, ProviderTestCase):
         f = QgsVectorLayerUtils.createFeature(vl)
         self.assertEqual(f.attributes(), [None, "qgis 'is good", 5, 5.7, None])
 
-        # check that provider passed attribute values take precedence over default literals
+        # check that provider default literals take precedence over passed attribute values
         f = QgsVectorLayerUtils.createFeature(vl, attributes={1: 'qgis is great', 0: 3})
-        self.assertEqual(f.attributes(), [3, "qgis is great", 5, 5.7, None])
+        self.assertEqual(f.attributes(), [3, "qgis 'is good", 5, 5.7, None])
 
-        # test take vector layer default value expression overrides postgres provider default clause
+        # test that vector layer default value expression overrides provider default literal
         vl.setDefaultValueExpression(3, "4*3")
         f = QgsVectorLayerUtils.createFeature(vl, attributes={1: 'qgis is great', 0: 3})
-        self.assertEqual(f.attributes(), [3, "qgis is great", 5, 12, None])
+        self.assertEqual(f.attributes(), [3, "qgis 'is good", 5, 12, None])
 
 if __name__ == '__main__':
     unittest.main()