Add support for dependent m2m fields

Author: codingjoe

django_select2/views.py

@@ -51,11 +51,20 @@ def get_queryset(self):
         kwargs = {
             model_field_name: self.request.GET.get(form_field_name)
             for form_field_name, model_field_name in self.widget.dependent_fields.items()
-            if form_field_name in self.request.GET
-            and self.request.GET.get(form_field_name, "") != ""
         }
+        kwargs.update(
+            {
+                f"{model_field_name}__in": filter(
+                    None, self.request.GET.get(f"{form_field_name}[]", "").split(",")
+                )
+                for form_field_name, model_field_name in self.widget.dependent_fields.items()
+            }
+        )
         return self.widget.filter_queryset(
-            self.request, self.term, self.queryset, **kwargs
+            self.request,
+            self.term,
+            self.queryset,
+            **{k: v for k, v in kwargs.items() if v},
         )
 
     def get_paginate_by(self, queryset):

tests/test_forms.py

@@ -200,7 +200,7 @@ def test_empty_css_setting(self, settings):
         settings.SELECT2_CSS = ""
         sut = Select2Widget()
         result = sut.media.render()
-        assert ".css" not in result
+        assert "/select2.css" not in result
 
 
 class TestHeavySelect2Mixin(TestSelect2Mixin):