ensure order of formset media. fixes #71

backport of fix to https://code.djangoproject.com/ticket/28377 . see
django/django@c19b56f

nested_admin/compat.py

@@ -0,0 +1,88 @@
+"""
+A backport of the fix in Django 2.0 that retains the order of form media.
+
+See https://github.com/django/django/commit/c19b56f633e172b3c02094cbe12d28865ee57772
+and https://code.djangoproject.com/ticket/28377
+"""
+import warnings
+
+import django.forms
+
+try:
+    from django.forms.widgets import MediaOrderConflictWarning
+except ImportError:
+    class MediaOrderConflictWarning(RuntimeWarning):
+        pass
+
+    MergeSafeMedia = None
+else:
+    MergeSafeMedia = django.forms.Media
+
+
+if MergeSafeMedia is None:
+    class MergeSafeMedia(django.forms.Media):
+        def __init__(self, media=None, css=None, js=None):
+            if media is not None:
+                css = getattr(media, '_css', {})
+                js = getattr(media, '_js', [])
+            else:
+                if css is None:
+                    css = {}
+                if js is None:
+                    js = []
+            self._css = css
+            self._js = js
+
+        @staticmethod
+        def merge(list_1, list_2):
+            """
+            Merge two lists while trying to keep the relative order of the elements.
+            Warn if the lists have the same two elements in a different relative
+            order.
+
+            For static assets it can be important to have them included in the DOM
+            in a certain order. In JavaScript you may not be able to reference a
+            global or in CSS you might want to override a style.
+            """
+            # Start with a copy of list_1.
+            combined_list = list(list_1)
+            last_insert_index = len(list_1)
+            # Walk list_2 in reverse, inserting each element into combined_list if
+            # it doesn't already exist.
+            for path in reversed(list_2):
+                try:
+                    # Does path already exist in the list?
+                    index = combined_list.index(path)
+                except ValueError:
+                    # Add path to combined_list since it doesn't exist.
+                    combined_list.insert(last_insert_index, path)
+                else:
+                    if index > last_insert_index:
+                        warnings.warn(
+                            'Detected duplicate Media files in an opposite order:\n'
+                            '%s\n%s' % (combined_list[last_insert_index], combined_list[index]),
+                            MediaOrderConflictWarning,
+                        )
+                    # path already exists in the list. Update last_insert_index so
+                    # that the following elements are inserted in front of this one.
+                    last_insert_index = index
+            return combined_list
+
+        def __add__(self, other):
+            combined = MergeSafeMedia()
+            combined._js = self.merge(self._js, other._js)
+            combined._css = {
+                medium: self.merge(self._css.get(medium, []), other._css.get(medium, []))
+                for medium in set(self._css.keys()) | set(other._css.keys())
+            }
+            return combined
+
+        def add_js(self, data):
+            if data:
+                new_media = self + MergeSafeMedia(js=data)
+                self._js = new_media._js
+
+        def add_css(self, data):
+            if data:
+                new_media = self + MergeSafeMedia(css=data)
+                self._css = new_media._css

nested_admin/nested.py

@@ -10,14 +10,14 @@
 except ImportError:
     # Django <= 1.9
     from django.core.urlresolvers import reverse
-from django import forms
 from django.template.defaultfilters import capfirst
 from django.utils import six
 from django.utils.six.moves import zip
 from django.utils.translation import ugettext
+from django.contrib.admin.options import ModelAdmin, InlineModelAdmin
 
+from .compat import MergeSafeMedia
 from .formsets import NestedInlineFormSet, NestedBaseGenericInlineFormSet
-from django.contrib.admin.options import ModelAdmin, InlineModelAdmin
 
 
 __all__ = (
@@ -63,7 +63,7 @@ def __iter__(self):
             yield inline_admin_form
 
     def _media(self):
-        media = self.opts.media + self.formset.media
+        media = MergeSafeMedia(self.formset.media) + self.opts.media
         for fs in self:
             media = media + fs.media
             for inline in (getattr(fs.form, 'inlines', None) or []):
@@ -73,7 +73,7 @@ def _media(self):
         static_url = staticfiles_storage.url
         server_data_js = reverse('nesting_server_data')
         min_ext = '' if getattr(settings, 'NESTED_ADMIN_DEBUG', False) else '.min'
-        return media + forms.Media(
+        return media + MergeSafeMedia(
             js=(
                 server_data_js,
                 static_url('nested_admin/dist/nested_admin%s.js' % min_ext),

nested_admin/tests/admin_widgets/admin.py

@@ -4,7 +4,9 @@
 from .models import (
     TestAdminWidgetsRoot, TestAdminWidgetsM2M, TestAdminWidgetsRelated1,
     TestAdminWidgetsRelated2, TestAdminWidgetsA, TestAdminWidgetsB,
-    TestAdminWidgetsC0, TestAdminWidgetsC1)
+    TestAdminWidgetsC0, TestAdminWidgetsC1,
+    TestWidgetMediaOrderRoot, TestWidgetMediaOrderA, TestWidgetMediaOrderB,
+    TestWidgetMediaOrderC0, TestWidgetMediaOrderC1)
 
 
 class TestAdminWidgetsC0Inline(NestedStackedInline):
@@ -60,3 +62,41 @@ class TestAdminWidgetsRootAdmin(NestedModelAdmin):
 admin.site.register(TestAdminWidgetsRelated1, NestedModelAdmin)
 admin.site.register(TestAdminWidgetsRelated2, NestedModelAdmin)
 admin.site.register(TestAdminWidgetsM2M, NestedModelAdmin)
+
+
+class TestWidgetMediaOrderC0Inline(NestedStackedInline):
+    model = TestWidgetMediaOrderC0
+    sortable_field_name = "position"
+    extra = 0
+    inline_classes = ("collapse", "open", "grp-collapse", "grp-open",)
+
+
+class TestWidgetMediaOrderC1Inline(NestedStackedInline):
+    model = TestWidgetMediaOrderC1
+    prepopulated_fields = {'slug': ('name', )}
+    filter_horizontal = ['m2m']
+    extra = 0
+    inline_classes = ("collapse", "open", "grp-collapse", "grp-open",)
+    raw_id_fields = ['fk2']
+    autocomplete_lookup_fields = {'fk': ['fk2']}
+
+
+class TestWidgetMediaOrderBInline(NestedStackedInline):
+    model = TestWidgetMediaOrderB
+    inlines = [TestWidgetMediaOrderC0Inline, TestWidgetMediaOrderC1Inline]
+    sortable_field_name = "position"
+    extra = 1
+    inline_classes = ("collapse", "open", "grp-collapse", "grp-open",)
+
+
+class TestWidgetMediaOrderAInline(NestedStackedInline):
+    model = TestWidgetMediaOrderA
+    inlines = [TestWidgetMediaOrderBInline]
+    sortable_field_name = "position"
+    extra = 1
+    inline_classes = ("collapse", "open", "grp-collapse", "grp-open",)
+
+
+@admin.register(TestWidgetMediaOrderRoot)
+class TestWidgetMediaOrderRootAdmin(NestedModelAdmin):
+    inlines = [TestWidgetMediaOrderAInline]

nested_admin/tests/admin_widgets/models.py

@@ -37,6 +37,7 @@ def __str__(self):
         return self.name
 
 
+@python_2_unicode_compatible
 class TestAdminWidgetsA(models.Model):
     name = models.CharField(max_length=200)
     slug = models.SlugField()
@@ -53,7 +54,11 @@ class TestAdminWidgetsA(models.Model):
     class Meta:
         ordering = ('position', )
 
+    def __str__(self):
+        return self.name
 
+
+@python_2_unicode_compatible
 class TestAdminWidgetsB(models.Model):
     name = models.CharField(max_length=200)
     slug = models.SlugField()
@@ -70,7 +75,12 @@ class TestAdminWidgetsB(models.Model):
     class Meta:
         ordering = ('position', )
 
+    def __str__(self):
+        parent_name = self.parent.name if self.parent else '?'
+        return "%s - %s" % (parent_name, self.name)
+
 
+@python_2_unicode_compatible
 class TestAdminWidgetsC0(models.Model):
     name = models.CharField(max_length=200)
     slug = models.SlugField()
@@ -87,7 +97,12 @@ class TestAdminWidgetsC0(models.Model):
     class Meta:
         ordering = ('position', )
 
+    def __str__(self):
+        parent_name = self.parent.name if self.parent else '?'
+        return "%s - %s" % (parent_name, self.name)
 
+
+@python_2_unicode_compatible
 class TestAdminWidgetsC1(models.Model):
     name = models.CharField(max_length=200)
     slug = models.SlugField()
@@ -103,3 +118,77 @@ class TestAdminWidgetsC1(models.Model):
 
     class Meta:
         ordering = ('position', )
+
+    def __str__(self):
+        parent_name = self.parent.name if self.parent else '?'
+        return "%s - %s" % (parent_name, self.name)
+
+
+class TestWidgetMediaOrderRoot(models.Model):
+    name = models.CharField(max_length=200)
+
+
+@python_2_unicode_compatible
+class TestWidgetMediaOrderA(models.Model):
+    name = models.CharField(max_length=200)
+    slug = models.SlugField()
+    parent = ForeignKey(TestWidgetMediaOrderRoot, on_delete=CASCADE)
+    position = models.PositiveIntegerField()
+
+    class Meta:
+        ordering = ('position', )
+
+    def __str__(self):
+        return self.name
+
+
+@python_2_unicode_compatible
+class TestWidgetMediaOrderB(models.Model):
+    name = models.CharField(max_length=200)
+    slug = models.SlugField()
+    parent = ForeignKey(TestWidgetMediaOrderA, on_delete=CASCADE)
+    position = models.PositiveIntegerField()
+
+    class Meta:
+        ordering = ('position', )
+
+    def __str__(self):
+        parent_name = self.parent.name if self.parent else '?'
+        return "%s - %s" % (parent_name, self.name)
+
+
+@python_2_unicode_compatible
+class TestWidgetMediaOrderC0(models.Model):
+    name = models.CharField(max_length=200)
+    slug = models.SlugField()
+    parent = ForeignKey(TestWidgetMediaOrderB, on_delete=CASCADE)
+    position = models.PositiveIntegerField()
+
+    class Meta:
+        ordering = ('position', )
+
+    def __str__(self):
+        parent_name = self.parent.name if self.parent else '?'
+        return "%s - %s" % (parent_name, self.name)
+
+
+@python_2_unicode_compatible
+class TestWidgetMediaOrderC1(models.Model):
+    name = models.CharField(max_length=200)
+    slug = models.SlugField()
+    parent = ForeignKey(TestWidgetMediaOrderB, on_delete=CASCADE)
+    position = models.PositiveIntegerField()
+    date = models.DateTimeField(blank=True, null=True)
+    upload = models.FileField(blank=True, null=True, upload_to='foo')
+    fk1 = models.ForeignKey(TestAdminWidgetsRelated1, blank=True, null=True,
+        on_delete=CASCADE, related_name='+')
+    fk2 = models.ForeignKey(TestAdminWidgetsRelated1, blank=True, null=True,
+        on_delete=CASCADE, related_name='+')
+    m2m = models.ManyToManyField(TestAdminWidgetsM2M, blank=True)
+
+    class Meta:
+        ordering = ('position', )
+
+    def __str__(self):
+        parent_name = self.parent.name if self.parent else '?'
+        return "%s - %s" % (parent_name, self.name)