Apply changes suggested by peterthomassen (conditionals + test)

Author: mgaligniana

rest_framework/renderers.py

@@ -339,22 +339,25 @@ def render_field(self, field, parent_style):
             style['template_pack'] = parent_style.get('template_pack', self.template_pack)
         style['renderer'] = self
 
-        # Get a clone of the field with text-only value representation.
+        # Get a clone of the field with text-only value representation ('' if None or False).
         field = field.as_form_field()
 
         if style.get('input_type') == 'datetime-local':
-            if hasattr(field._field, "format"):
-                if field._field.format is None:
-                    # `to_representation` returned a Python datetime object
-                    # https://www.django-rest-framework.org/api-guide/fields/#datetimefield
-                    datetime_field_value = field.value
-                else:
-                    datetime_field_value = datetime.datetime.strptime(field.value, field._field.format)
+            try:
+                format = field._field.format
+            except AttributeError:
+                format = api_settings.DATETIME_FORMAT
+
+            if format is None:
+                # field.value is a datetime
+                # https://www.django-rest-framework.org/api-guide/fields/#datetimefield
+                datetime_field_value = field.value
             else:
-                if api_settings.DATETIME_FORMAT == ISO_8601:
-                    datetime_field_value = datetime.datetime.fromisoformat(field.value.rstrip('Z'))
-                else:
-                    datetime_field_value = datetime.datetime.strptime(field.value, api_settings.DATETIME_FORMAT)
+                # field.value is expected to be a string
+                datetime_field_value = (
+                    datetime.datetime.fromisoformat(field.value.rstrip('Z')) if format == ISO_8601
+                    else datetime.datetime.strptime(field.value, format)
+                )
 
             # The format of an input type="datetime-local" is "yyyy-MM-ddThh:mm"
             # followed by optional ":ss" or ":ss.SSS", so keep only the first three

tests/test_renderers.py

@@ -556,6 +556,13 @@ def test_datetime_field_rendering_with_custom_datetime_format(self):
             "2024-12-24T00:55:00.000"
         )
 
+    @override_settings(REST_FRAMEWORK={'DATETIME_FORMAT': None})
+    def test_datetime_field_rendering_datetime_format_is_none(self):
+        self._assert_datetime_rendering(
+            datetime(2024, 12, 24, 0, 55, 30, 345678),
+            "2024-12-24T00:55:30.345"
+        )
+
 
 class TestHTMLFormRenderer(TestCase):
     def setUp(self):