Fix partial form data updates involving ListField

rest_framework/fields.py

@@ -1675,17 +1675,25 @@ def __init__(self, **kwargs):
             self.validators.append(MinLengthValidator(self.min_length, message=message))
 
     def get_value(self, dictionary):
-        if self.field_name not in dictionary:
-            if getattr(self.root, 'partial', False):
-                return empty
         # We override the default field access in order to support
         # lists in HTML forms.
         if html.is_html_input(dictionary):
             val = dictionary.getlist(self.field_name, [])
             if len(val) > 0:
                 # Support QueryDict lists in HTML input.
                 return val
-            return html.parse_html_list(dictionary, prefix=self.field_name, default=empty)
+            # Check for indexed keys like field_name[0], field_name[1], etc.
+            # before returning empty on partial updates
+            html_list = html.parse_html_list(dictionary, prefix=self.field_name, default=empty)
+            if html_list is not empty:
+                return html_list
+            # If no HTML list data found and this is a partial update, return empty
+            if getattr(self.root, 'partial', False):
+                return empty
+            return html_list
+        if self.field_name not in dictionary:
+            if getattr(self.root, 'partial', False):
+                return empty
 
         return dictionary.get(self.field_name, empty)
 

tests/test_serializer_lists.py

@@ -426,6 +426,28 @@ class MultipleChoiceSerializer(serializers.Serializer):
         assert serializer.validated_data == {}
         assert serializer.errors == {}
 
+    def test_partial_listfield_with_indexed_keys(self):
+        """
+        Test that ListField respects ordered sequence in form data with partial updates.
+        Regression test for GitHub issue where indexed keys like field[0], field[1]
+        were not being parsed in partial updates.
+        """
+        class CommunitySerializer(serializers.Serializer):
+            colors = serializers.ListField(
+                allow_null=True,
+                child=serializers.CharField(label='Colors', max_length=7),
+                required=False
+            )
+        # Simulate form data with indexed keys
+        data = MultiValueDict({
+            'colors[0]': ['#ffffff'],
+            'colors[1]': ['#000000']
+        })
+        serializer = CommunitySerializer(data=data, partial=True)
+        assert serializer.is_valid(), f"Expected valid but got errors: {serializer.errors}"
+        assert 'colors' in serializer.validated_data
+        assert serializer.validated_data['colors'] == ['#ffffff', '#000000']
+
     def test_allow_empty_true(self):
         class ListSerializer(serializers.Serializer):
             update_field = serializers.IntegerField()