Add ability to specify the form for radio input

src/django_bootstrap5/templates/django_bootstrap5/widgets/radio_select.html

@@ -12,6 +12,7 @@
                        id="{{ option.attrs.id }}"
                         {% if option.value != None %} value="{{ option.value|stringformat:'s' }}"
                             {% if option.attrs.checked %} checked="checked"{% endif %}{% endif %}
+                        {% if widget.attrs.form %} form="{{ widget.attrs.form }}{% endif %}
                         {% if widget.attrs.disabled %} disabled{% endif %}>
                 <label class="form-check-label" for="{{ option.attrs.id }}">{{ option.label }}</label>
             </div>

tests/test_bootstrap_field_radio_select.py

@@ -22,6 +22,15 @@ class DisabledSelectTestForm(forms.Form):
         widget=forms.RadioSelect,
         disabled=True,
     )
+
+
+class SelectOtherTestForm(forms.Form):
+    test = forms.ChoiceField(
+        choices=(
+            (1, "one"),
+            (2, "two"),
+        ),
+        widget=forms.RadioSelect(attrs={"form": "another-form"})
 
 
 class BootstrapFieldSelectTestCase(BootstrapTestCase):
@@ -111,3 +120,25 @@ def test_disabled_select(self):
                 "</div>"
             ),
         )
+
+    def test_other_form_select(self):
+        """Test field with select that belongs to another form widget."""
+        self.maxDiff = None
+        self.assertHTMLEqual(
+            self.render("{% bootstrap_field form.test %}", context={"form": DisabledSelectTestForm()}),
+            (
+                '<div class="django_bootstrap5-req mb-3">'
+                '<label class="form-label">Test</label>'
+                '<div class="" disabled required id="id_test">'
+                '<div class="form-check">'
+                '<input class="form-check-input" form="another-form" type="radio" name="test" id="id_test_0" value="1">'
+                '<label class="form-check-label" for="id_test_0">one</label>'
+                "</div>"
+                '<div class="form-check">'
+                '<input class="form-check-input" form="another-form" type="radio" name="test" id="id_test_1" value="2">'
+                '<label class="form-check-label" for="id_test_1">two</label>'
+                "</div>"
+                "</div>"
+                "</div>"
+            ),
+        )