From dd11d8acf1dec571cd1d130e191091c6039e925d Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Tue, 11 Feb 2025 15:05:58 +1000
Subject: [PATCH 1/3] Add provider test for adding feature with all null
 attributes

---
 tests/src/python/providertestbase.py | 38 ++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/tests/src/python/providertestbase.py b/tests/src/python/providertestbase.py
index 073ada0f14f9..6355499210a0 100644
--- a/tests/src/python/providertestbase.py
+++ b/tests/src/python/providertestbase.py
@@ -1139,6 +1139,44 @@ def testAddFeatureExtraAttributes(self):
             ],
         )
 
+    def testAddFeatureAllNull(self):
+        if not getattr(self, "getEditableLayer", None):
+            return
+
+        l = self.getEditableLayer()
+        self.assertTrue(l.isValid())
+
+        f1 = QgsFeature()
+        f1.setAttributes([NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL])
+        f1.setGeometry(QgsGeometry.fromWkt("Point (-72.345 71.987)"))
+
+        if (
+            l.dataProvider().capabilities()
+            & QgsVectorDataProvider.Capability.AddFeatures
+        ):
+            # expect success
+            result, added = l.dataProvider().addFeatures([f1])
+            self.assertTrue(
+                result,
+                "Provider reported AddFeatures capability, but returned False to addFeatures",
+            )
+
+            # check result
+            f_new = next(
+                l.dataProvider().getFeatures(
+                    QgsFeatureRequest().setFilterFid(added[0].id())
+                )
+            )
+            self.assertEqual(
+                f_new.attributes()[1:], [NULL, NULL, NULL, NULL, NULL, NULL, NULL]
+            )
+        else:
+            # expect fail
+            self.assertFalse(
+                l.dataProvider().addFeatures([f1]),
+                "Provider reported no AddFeatures capability, but returned true to addFeatures",
+            )
+
     def testAddFeatureWrongGeomType(self):
         if not getattr(self, "getEditableLayer", None):
             return

From 398fc2c30add367ae8ab968ef32b9b0247ce1e15 Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Tue, 11 Feb 2025 11:27:58 +1000
Subject: [PATCH 2/3] [oracle] Fix handling of type null variants

---
 src/providers/oracle/qgsoracleprovider.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/providers/oracle/qgsoracleprovider.cpp b/src/providers/oracle/qgsoracleprovider.cpp
index 3e070a29c93a..f154bbfc8f00 100644
--- a/src/providers/oracle/qgsoracleprovider.cpp
+++ b/src/providers/oracle/qgsoracleprovider.cpp
@@ -1394,10 +1394,16 @@ bool QgsOracleProvider::addFeatures( QgsFeatureList &flist, QgsFeatureSink::Flag
         QVariant value = attributevec.value( fieldId[i], QVariant() );
 
         QgsField fld = field( fieldId[i] );
-        if ( ( value.isNull() && mPrimaryKeyAttrs.contains( i ) && !defaultValues.at( i ).isEmpty() ) || ( value.toString() == defaultValues[i] ) )
+        if ( ( QgsVariantUtils::isNull( value ) && mPrimaryKeyAttrs.contains( i ) && !defaultValues.at( i ).isEmpty() ) || ( value.toString() == defaultValues[i] ) )
         {
           value = evaluateDefaultExpression( defaultValues[i], fld.type() );
         }
+        else if ( QgsVariantUtils::isNull( value ) )
+        {
+          // don't use typed null variants, always use invalid variants. Otherwise the connection
+          // may incorrectly try to coerce a null value to the variant type
+          value = QVariant();
+        }
         features->setAttribute( fieldId[i], value );
 
         QgsDebugMsgLevel( QStringLiteral( "addBindValue: %1" ).arg( value.toString() ), 4 );

From c9cc3bd53be9a05255d87b7db4df163dd5777b9e Mon Sep 17 00:00:00 2001
From: Nyall Dawson <nyall.dawson@gmail.com>
Date: Wed, 12 Feb 2025 06:23:58 +1000
Subject: [PATCH 3/3] Override base test to account for extra attributes in
 layer

---
 tests/src/python/test_provider_postgres.py | 40 ++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/tests/src/python/test_provider_postgres.py b/tests/src/python/test_provider_postgres.py
index fbd4e98279eb..c6cd57c785f7 100644
--- a/tests/src/python/test_provider_postgres.py
+++ b/tests/src/python/test_provider_postgres.py
@@ -4960,6 +4960,46 @@ def testAddFeatureMissingAttributes(self):
         f2.setAttributes([7, 330, "qgis", "qgis", NULL])
         self.testGetFeatures(l.dataProvider(), [f1, f2])
 
+    def testAddFeatureAllNull(self):
+        # overridden from base test because of extra attributes in layer
+        if not getattr(self, "getEditableLayer", None):
+            return
+
+        l = self.getEditableLayer()
+        self.assertTrue(l.isValid())
+
+        f1 = QgsFeature()
+        f1.setAttributes([8, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL])
+        f1.setGeometry(QgsGeometry.fromWkt("Point (-72.345 71.987)"))
+
+        if (
+            l.dataProvider().capabilities()
+            & QgsVectorDataProvider.Capability.AddFeatures
+        ):
+            # expect success
+            result, added = l.dataProvider().addFeatures([f1])
+            self.assertTrue(
+                result,
+                "Provider reported AddFeatures capability, but returned False to addFeatures",
+            )
+
+            # check result
+            f_new = next(
+                l.dataProvider().getFeatures(
+                    QgsFeatureRequest().setFilterFid(added[0].id())
+                )
+            )
+            self.assertEqual(
+                f_new.attributes(),
+                [8, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL],
+            )
+        else:
+            # expect fail
+            self.assertFalse(
+                l.dataProvider().addFeatures([f1]),
+                "Provider reported no AddFeatures capability, but returned true to addFeatures",
+            )
+
     def testAddFeature(self):
         if not getattr(self, "getEditableLayer", None):
             return