From 82648ab7aef44d007d96700ba2af0800cc9cfc6a Mon Sep 17 00:00:00 2001
From: Matthias Kuhn <matthias@opengis.ch>
Date: Tue, 23 Nov 2021 07:47:34 +0100
Subject: [PATCH 1/3] Preserve data types for default values

when they are created in the attribute dialog
Fixes #46158
---
 src/gui/qgsattributeform.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/gui/qgsattributeform.cpp b/src/gui/qgsattributeform.cpp
index 3324e0e6cb5..f408bee3a62 100644
--- a/src/gui/qgsattributeform.cpp
+++ b/src/gui/qgsattributeform.cpp
@@ -551,7 +551,7 @@ void QgsAttributeForm::updateValuesDependenciesDefaultValues( const int originId
           continue;
 
         QgsExpressionContext context = createExpressionContext( updatedFeature );
-        QString value = mLayer->defaultValue( eww->fieldIdx(), updatedFeature, &context ).toString();
+        const QVariant value = mLayer->defaultValue( eww->fieldIdx(), updatedFeature, &context );
         eww->setValue( value );
       }
     }

From 6e745614af4e49f747b756157da2e3b04f21ff36 Mon Sep 17 00:00:00 2001
From: Matthias Kuhn <matthias@opengis.ch>
Date: Tue, 23 Nov 2021 22:45:33 +0100
Subject: [PATCH 2/3] Update form feature with live values

---
 src/gui/qgsattributeform.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/gui/qgsattributeform.cpp b/src/gui/qgsattributeform.cpp
index f408bee3a62..5cc8091008a 100644
--- a/src/gui/qgsattributeform.cpp
+++ b/src/gui/qgsattributeform.cpp
@@ -553,6 +553,7 @@ void QgsAttributeForm::updateValuesDependenciesDefaultValues( const int originId
         QgsExpressionContext context = createExpressionContext( updatedFeature );
         const QVariant value = mLayer->defaultValue( eww->fieldIdx(), updatedFeature, &context );
         eww->setValue( value );
+        mCurrentFormFeature.setAttribute( eww->field().name(), value );
       }
     }
   }

From c1b8722eb98aea247a68099801c980de3ad1786a Mon Sep 17 00:00:00 2001
From: Matthias Kuhn <matthias@opengis.ch>
Date: Tue, 23 Nov 2021 22:46:05 +0100
Subject: [PATCH 3/3] Add test for live value update

---
 tests/Testing/Temporary/CTestCostData.txt |  1 +
 tests/src/python/test_qgsattributeform.py | 28 ++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 tests/Testing/Temporary/CTestCostData.txt

diff --git a/tests/Testing/Temporary/CTestCostData.txt b/tests/Testing/Temporary/CTestCostData.txt
new file mode 100644
index 00000000000..ed97d539c09
--- /dev/null
+++ b/tests/Testing/Temporary/CTestCostData.txt
@@ -0,0 +1 @@
+---
diff --git a/tests/src/python/test_qgsattributeform.py b/tests/src/python/test_qgsattributeform.py
index 930ff3347a7..58cfeab4852 100644
--- a/tests/src/python/test_qgsattributeform.py
+++ b/tests/src/python/test_qgsattributeform.py
@@ -22,13 +22,17 @@ from qgis.core import (
     QgsEditorWidgetSetup,
     QgsEditFormConfig,
     QgsAttributeEditorElement,
+    QgsDefaultValue,
+    QgsField
 )
 from qgis.gui import (
     QgsAttributeForm,
     QgsGui,
     QgsEditorWidgetWrapper,
-    QgsMapCanvas
+    QgsMapCanvas,
+    QgsAttributeEditorContext
 )
+from qgis.PyQt.QtCore import QVariant
 
 QGISAPP = start_app()
 
@@ -115,6 +119,28 @@ class TestQgsAttributeForm(unittest.TestCase):
         for field_type, value in field_types.items():
             self.checkForm(field_type, value)
 
+    def test_on_update(self):
+        """Test live update"""
+
+        layer = QgsVectorLayer("Point?field=age:int", "vl", "memory")
+        # set default value for numbers to [1, {age}], it will depend on the field age and should update
+        field = QgsField('numbers', QVariant.List, 'array')
+        field.setEditorWidgetSetup(QgsEditorWidgetSetup('List', {}))
+        layer.dataProvider().addAttributes([field])
+        layer.updateFields()
+        layer.setDefaultValueDefinition(1, QgsDefaultValue('array(1, age)', True))
+        layer.setEditorWidgetSetup(1, QgsEditorWidgetSetup('List', {}))
+        layer.startEditing()
+        form = QgsAttributeForm(layer)
+        feature = QgsFeature(layer.fields())
+        form.setFeature(feature)
+        form.setMode(QgsAttributeEditorContext.AddFeatureMode)
+        form.changeAttribute('numbers', [12])
+        form.changeAttribute('age', 1)
+        self.assertEqual(form.currentFormFeature()['numbers'], [1, 1])
+        form.changeAttribute('age', 7)
+        self.assertEqual(form.currentFormFeature()['numbers'], [1, 7])
+
 
 if __name__ == '__main__':
     unittest.main()