Improved SparseVectorField forms for Django

pgvector/django/sparsevec.py

@@ -1,3 +1,4 @@
+from django import forms
 from django.db.models import Field
 from ..utils import SparseVector
 
@@ -33,3 +34,13 @@ def get_prep_value(self, value):
 
     def value_to_string(self, obj):
         return self.get_prep_value(self.value_from_object(obj))
+
+    def formfield(self, **kwargs):
+        return super().formfield(form_class=SparseVectorFormField, **kwargs)
+
+
+class SparseVectorFormField(forms.CharField):
+    def to_python(self, value):
+        if isinstance(value, str) and value == '':
+            return None
+        return super().to_python(value)

tests/test_django.py

@@ -385,6 +385,14 @@ def test_sparsevec_form_save(self):
         assert form.save()
         assert [4, 5, 6] == Item.objects.get(pk=1).sparse_embedding.to_list()
 
+    def test_sparesevec_form_save_missing(self):
+        Item(id=1).save()
+        item = Item.objects.get(pk=1)
+        form = SparseVectorForm(instance=item, data={'sparse_embedding': ''})
+        assert form.is_valid()
+        assert form.save()
+        assert Item.objects.get(pk=1).sparse_embedding is None
+
     def test_clean(self):
         item = Item(id=1, embedding=[1, 2, 3], half_embedding=[1, 2, 3], binary_embedding='101', sparse_embedding=SparseVector.from_dense([1, 2, 3]))
         item.full_clean()