Fixed #19581 -- ensure unique html ids with CheckboxSelectMultiple widgets

ID check is now done the same way as MultipleHiddenInput.

2 files changed, 11 insertions, 4 deletions

diff --git a/django/forms/widgets.py b/django/forms/widgets.py
index 4782b99117..d6ea56f0c8 100644
--- a/django/forms/widgets.py
+++ b/django/forms/widgets.py
@@ -754,17 +754,17 @@ class RadioSelect(Select):
 class CheckboxSelectMultiple(SelectMultiple):
     def render(self, name, value, attrs=None, choices=()):
         if value is None: value = []
-        has_id = attrs and 'id' in attrs
         final_attrs = self.build_attrs(attrs, name=name)
+        id_ = final_attrs.get('id', None)
         output = ['<ul>']
         # Normalize to strings
         str_values = set([force_text(v) for v in value])
         for i, (option_value, option_label) in enumerate(chain(self.choices, choices)):
             # If an ID attribute was given, add a numeric index as a suffix,
             # so that the checkboxes don't all have the same ID attribute.
-            if has_id:
-                final_attrs = dict(final_attrs, id='%s_%s' % (attrs['id'], i))
-                label_for = format_html(' for="{0}"', final_attrs['id'])
+            if id_:
+                final_attrs = dict(final_attrs, id='%s_%s' % (id_, i))
+                label_for = format_html(' for="{0}_{1}"', id_, i)
             else:
                 label_for = ''
 
diff --git a/tests/regressiontests/forms/tests/widgets.py b/tests/regressiontests/forms/tests/widgets.py
index f9dc4a7ec8..7a2961358a 100644
--- a/tests/regressiontests/forms/tests/widgets.py
+++ b/tests/regressiontests/forms/tests/widgets.py
@@ -863,6 +863,13 @@ beatle J R Ringo False""")
 <li><label for="abc_2"><input checked="checked" type="checkbox" name="letters" value="c" id="abc_2" /> C</label></li>
 </ul>""")
 
+        # Each input gets a separate ID when the ID is passed to the constructor
+        self.assertHTMLEqual(CheckboxSelectMultiple(attrs={'id': 'abc'}).render('letters', list('ac'), choices=zip(list('abc'), list('ABC'))), """<ul>
+<li><label for="abc_0"><input checked="checked" type="checkbox" name="letters" value="a" id="abc_0" /> A</label></li>
+<li><label for="abc_1"><input type="checkbox" name="letters" value="b" id="abc_1" /> B</label></li>
+<li><label for="abc_2"><input checked="checked" type="checkbox" name="letters" value="c" id="abc_2" /> C</label></li>
+</ul>""")
+
     def test_multi(self):
         class MyMultiWidget(MultiWidget):
             def decompress(self, value):