[fix] Fixed re-ordering templates on device add page #434

Closes #434

openwisp_controller/config/sortedm2m/fields.py

@@ -14,6 +14,8 @@
     create_sorted_many_related_manager as base_create_sorted_many_related_manager,
 )
 
+from .forms import SortedMultipleChoiceField
+
 
 def create_sorted_many_related_manager(superclass, rel, *args, **kwargs):
     BaseSortedRelatedManager = base_create_sorted_many_related_manager(
@@ -64,3 +66,12 @@ class SortedManyToManyField(BaseSortedManyToManyField):
     def contribute_to_class(self, cls, name, **kwargs):
         super().contribute_to_class(cls, name, **kwargs)
         setattr(cls, self.name, SortedManyToManyDescriptor(self))
+
+    def formfield(self, **kwargs):
+        # TODO: Remove this when stacked inline admin is fixed in django-sortedm2m
+        # https://github.com/jazzband/django-sortedm2m/pull/213
+        defaults = {}
+        if self.sorted:
+            defaults['form_class'] = SortedMultipleChoiceField
+        defaults.update(kwargs)
+        return super().formfield(**defaults)

openwisp_controller/config/sortedm2m/forms.py

@@ -0,0 +1,24 @@
+from sortedm2m.forms import (
+    SortedCheckboxSelectMultiple as BaseSortedCheckboxSelectMultiple,
+)
+from sortedm2m.forms import SortedMultipleChoiceField as BaseSortedMultipleChoiceField
+
+
+class SortedCheckboxSelectMultiple(BaseSortedCheckboxSelectMultiple):
+    class Media(BaseSortedCheckboxSelectMultiple.Media):
+        # The django-sortedm2m library has a bug when the widget is
+        # use in StackedInline Admin, see
+        # https://github.com/jazzband/django-sortedm2m/pull/213
+        # The workaround in sortedm2m/patch_sortedm2m.js fixes the bug.
+        # TODO: Remove this workaround when a new version of django-sortedm2m
+        # is released.
+        js = (
+            'admin/js/jquery.init.js',
+            'sortedm2m/widget.js',
+            'sortedm2m/jquery-ui.js',
+            'sortedm2m/patch_sortedm2m.js',
+        )
+
+
+class SortedMultipleChoiceField(BaseSortedMultipleChoiceField):
+    widget = SortedCheckboxSelectMultiple

openwisp_controller/config/static/sortedm2m/patch_sortedm2m.js

@@ -0,0 +1,6 @@
+'use strict';
+(function ($) {
+    $(document).ready( function () {
+        $('.sortedm2m-items').sortable('destroy');
+    });
+}(django.jQuery));