Ensure empty string values are converted to None

src/backend/InvenTree/common/serializers.py

@@ -733,6 +733,10 @@ class ParameterTemplateSerializer(
         allow_null=True,
     )
 
+    def validate_model_type(self, model_type):
+        """Convert an empty string to None for the model_type field."""
+        return model_type or None
+
 
 @register_importer()
 class ParameterSerializer(

src/backend/InvenTree/common/test_api.py

@@ -121,6 +121,19 @@ class ParameterAPITests(InvenTreeAPITestCase):
         self.assertEqual(common.models.ParameterTemplate.objects.count(), N)
         self.assertFalse(common.models.ParameterTemplate.objects.filter(pk=pk).exists())
 
+        # Let's create a template which does not specify a model_type
+        data = {
+            'name': 'Universal Parameter',
+            'units': '',
+            'description': 'A parameter template for all models',
+            'enabled': False,
+        }
+
+        response = self.post(url, data, expected_code=201)
+
+        self.assertIsNone(response.data['model_type'])
+        self.assertFalse(response.data['enabled'])
+
     def test_template_filters(self):
         """Tests for API filters against ParameterTemplate endpoint."""
         from company.models import Company

src/backend/InvenTree/part/test_api.py

@@ -3330,11 +3330,11 @@ class PartTestTemplateTest(PartAPITestBase):
         self.assertIn('Choices must be unique', str(response.data['choices']))
 
 
-class PartParameterTests(PartAPITestBase):
+class ParameterTests(PartAPITestBase):
-    """Unit test for PartParameter API endpoints."""
+    """Unit test for Parameter API endpoints."""
 
     def test_export_data(self):
-        """Test data export functionality for PartParameter objects."""
+        """Test data export functionality for Parameter objects."""
         url = reverse('api-parameter-list')
 
         response = self.options(

src/backend/InvenTree/part/test_param.py

@@ -287,8 +287,8 @@ class ParameterTests(TestCase):
             self.assertAlmostEqual(param.data_numeric, expected, places=2)
 
 
-class PartParameterTest(InvenTreeAPITestCase):
+class ParameterTest(InvenTreeAPITestCase):
-    """Tests for the ParParameter API."""
+    """Tests for the Parameter API."""
 
     superuser = True
 
@@ -496,7 +496,7 @@ class PartParameterTest(InvenTreeAPITestCase):
             self.assertEqual(actual, expected)
 
 
-class PartParameterFilterTest(InvenTreeAPITestCase):
+class ParameterFilterTest(InvenTreeAPITestCase):
     """Unit tests for filtering parts by parameter values."""
 
     superuser = True