Use datetime value to render datetime-local input_type

Author: mgaligniana

rest_framework/renderers.py

@@ -342,15 +342,12 @@ def render_field(self, field, parent_style):
         # Get a clone of the field with text-only value representation.
         field = field.as_form_field()
 
-        if style.get('input_type') == 'datetime-local' and isinstance(field.value, str):
+        if style.get('input_type') == 'datetime-local':
             # 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
             # digits of milliseconds to avoid browser console error.
-            datetime_parts = field.value.split(".")
-            if len(datetime_parts) > 1:
-                field.value = f"{datetime_parts[0]}.{datetime_parts[1][:3]}"
-            else:
-                field.value = field.value.rstrip('Z')
+            datetime_value = field._field.parent.validated_data.get(field.field_name)
+            field.value = datetime_value.replace(tzinfo=None).isoformat(timespec="milliseconds").rstrip('Z')
 
         if 'template' in style:
             template_name = style['template']

tests/test_renderers.py

@@ -489,7 +489,6 @@ class TestSerializer(serializers.Serializer):
         assert rendered == ''
 
 
-@override_settings(TIME_ZONE='UTC', USE_TZ=True)
 class TestDateTimeFieldHTMLFormRender(TestCase):
     def test_datetime_field_rendering_milliseconds(self):
         class TestSerializer(serializers.Serializer):
@@ -517,11 +516,11 @@ class TestSerializer(serializers.Serializer):
         field = serializer['appointment']
         rendered = renderer.render_field(field, {})
         self.assertInHTML(
-            '<input name="appointment" class="form-control" type="datetime-local" value="2024-12-24T00:55:30">',
+            '<input name="appointment" class="form-control" type="datetime-local" value="2024-12-24T00:55:30.000">',
             rendered
         )
 
-    def test_datetime_field_rendering_no_seconds_and_milliseconds(self):
+    def test_datetime_field_rendering_no_seconds_and_no_milliseconds(self):
         class TestSerializer(serializers.Serializer):
             appointment = serializers.DateTimeField()
 
@@ -532,7 +531,22 @@ class TestSerializer(serializers.Serializer):
         field = serializer['appointment']
         rendered = renderer.render_field(field, {})
         self.assertInHTML(
-            '<input name="appointment" class="form-control" type="datetime-local" value="2024-12-24T00:55:00">',
+            '<input name="appointment" class="form-control" type="datetime-local" value="2024-12-24T00:55:00.000">',
+            rendered
+        )
+
+    def test_datetime_field_rendering_with_format(self):
+        class TestSerializer(serializers.Serializer):
+            appointment = serializers.DateTimeField(format='%a %d %b %Y, %I:%M%p')
+
+        appointment = datetime(2024, 12, 24, 0, 55, 30, 345678)
+        serializer = TestSerializer(data={"appointment": appointment})
+        serializer.is_valid()
+        renderer = HTMLFormRenderer()
+        field = serializer['appointment']
+        rendered = renderer.render_field(field, {})
+        self.assertInHTML(
+            '<input name="appointment" class="form-control" type="datetime-local" value="2024-12-24T00:55:30.345">',
             rendered
         )