Fixed #19721 -- Allowed admin filters to customize the list separator.

django/contrib/admin/filters.py

@@ -118,6 +118,7 @@ class SimpleListFilter(ListFilter):
 class FieldListFilter(ListFilter):
     _field_list_filters = []
     _take_priority_index = 0
+    list_separator = ','
 
     def __init__(self, field, request, params, model, model_admin, field_path):
         self.field = field
@@ -127,7 +128,7 @@ class FieldListFilter(ListFilter):
         for p in self.expected_parameters():
             if p in params:
                 value = params.pop(p)
-                self.used_parameters[p] = prepare_lookup_value(p, value)
+                self.used_parameters[p] = prepare_lookup_value(p, value, self.list_separator)
 
     def has_output(self):
         return True

django/contrib/admin/utils.py

@@ -51,13 +51,13 @@ def lookup_spawns_duplicates(opts, lookup_path):
     return False
 
 
-def prepare_lookup_value(key, value):
+def prepare_lookup_value(key, value, separator=','):
     """
     Return a lookup value prepared to be used in queryset filtering.
     """
     # if key ends with __in, split parameter into separate values
     if key.endswith('__in'):
-        value = value.split(',')
+        value = value.split(separator)
     # if key ends with __isnull, special case '' and the string literals 'false' and '0'
     elif key.endswith('__isnull'):
         value = value.lower() not in ('', 'false', '0')

docs/ref/contrib/admin/filters.txt

@@ -176,6 +176,25 @@ allows to store::
             ('title', admin.EmptyFieldListFilter),
         )
 
+By defining a filter using the ``__in`` lookup, it is possible to filter for
+any of a group of values. You need to override the ``expected_parameters``
+method, and the specify the ``lookup_kwargs`` attribute with the appropriate
+field name. By default, multiple values in the query string will be separated
+with commas, but this can be customized via the ``list_separator`` attribute.
+The following example shows such a filter using the vertical-pipe character as
+the separator::
+
+    class FilterWithCustomSeparator(admin.FieldListFilter):
+        # custom list separator that should be used to separate values.
+        list_separator = '|'
+
+        def __init__(self, field, request, params, model, model_admin, field_path):
+            self.lookup_kwarg = '%s__in' % field_path
+            super().__init__(field, request, params, model, model_admin, field_path)
+
+        def expected_parameters(self):
+            return [self.lookup_kwarg]
+
 .. note::
 
     The :class:`~django.contrib.contenttypes.fields.GenericForeignKey` field is

docs/releases/4.1.txt

@@ -54,6 +54,10 @@ Minor features
 * The admin :ref:`dark mode CSS variables <admin-theming>` are now applied in a
   separate stylesheet and template block.
 
+* :ref:`modeladmin-list-filters` providing custom ``FieldListFilter``
+  subclasses can now control the query string value separator when filtering
+  for multiple values using the ``__in`` lookup.
+
 :mod:`django.contrib.admindocs`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

tests/admin_filters/tests.py

@@ -4,7 +4,8 @@ import unittest
 
 from django.contrib.admin import (
     AllValuesFieldListFilter, BooleanFieldListFilter, EmptyFieldListFilter,
-    ModelAdmin, RelatedOnlyFieldListFilter, SimpleListFilter, site,
+    FieldListFilter, ModelAdmin, RelatedOnlyFieldListFilter, SimpleListFilter,
+    site,
 )
 from django.contrib.admin.options import IncorrectLookupParameters
 from django.contrib.auth.admin import UserAdmin
@@ -135,6 +136,17 @@ class DepartmentListFilterLookupWithDynamicValue(DecadeListFilterWithTitleAndPar
             return (('the 80s', "the 1980's"), ('the 90s', "the 1990's"),)
 
 
+class EmployeeNameCustomDividerFilter(FieldListFilter):
+    list_separator = '|'
+
+    def __init__(self, field, request, params, model, model_admin, field_path):
+        self.lookup_kwarg = '%s__in' % field_path
+        super().__init__(field, request, params, model, model_admin, field_path)
+
+    def expected_parameters(self):
+        return [self.lookup_kwarg]
+
+
 class CustomUserAdmin(UserAdmin):
     list_filter = ('books_authored', 'books_contributed')
 
@@ -231,6 +243,12 @@ class EmployeeAdmin(ModelAdmin):
     list_filter = ['department']
 
 
+class EmployeeCustomDividerFilterAdmin(EmployeeAdmin):
+    list_filter = [
+        ('name', EmployeeNameCustomDividerFilter),
+    ]
+
+
 class DepartmentFilterEmployeeAdmin(EmployeeAdmin):
     list_filter = [DepartmentListFilterLookupWithNonStringValue]
 
@@ -1547,3 +1565,29 @@ class ListFiltersTests(TestCase):
         request.user = self.alfred
         with self.assertRaises(IncorrectLookupParameters):
             modeladmin.get_changelist_instance(request)
+
+    def test_lookup_using_custom_divider(self):
+        """
+        Filter __in lookups with a custom divider.
+        """
+        jane = Employee.objects.create(name='Jane,Green', department=self.design)
+        modeladmin = EmployeeCustomDividerFilterAdmin(Employee, site)
+        employees = [jane, self.jack]
+
+        request = self.request_factory.get(
+            '/', {'name__in': "|".join(e.name for e in employees)}
+        )
+        # test for lookup with custom divider
+        request.user = self.alfred
+        changelist = modeladmin.get_changelist_instance(request)
+        # Make sure the correct queryset is returned
+        queryset = changelist.get_queryset(request)
+        self.assertEqual(list(queryset), employees)
+
+        # test for lookup with comma in the lookup string
+        request = self.request_factory.get('/', {'name': jane.name})
+        request.user = self.alfred
+        changelist = modeladmin.get_changelist_instance(request)
+        # Make sure the correct queryset is returned
+        queryset = changelist.get_queryset(request)
+        self.assertEqual(list(queryset), [jane])