Fixed #19082 -- Enabled admin field pre-population for existing objects.

Thanks to msaelices and d1ffuz0r for the initial patch and tests.

django/contrib/admin/static/admin/js/prepopulate.js

@@ -4,31 +4,36 @@
             Depends on urlify.js
             Populates a selected field with the values of the dependent fields,
             URLifies and shortens the string.
-            dependencies - array of dependent fields id's 
+            dependencies - array of dependent fields ids
             maxLength - maximum length of the URLify'd string
         */
         return this.each(function() {
-            var field = $(this);
-
-            field.data('_changed', false);
-            field.change(function() {
-                field.data('_changed', true);
-            });
+            var prepopulatedField = $(this);
 
             var populate = function () {
-                // Bail if the fields value has changed
-                if (field.data('_changed') == true) return;
+                // Bail if the field's value has been changed by the user
+                if (prepopulatedField.data('_changed')) {
+                    return;
+                }
 
                 var values = [];
                 $.each(dependencies, function(i, field) {
-                  if ($(field).val().length > 0) {
-                      values.push($(field).val());
-                  }
-                })
-                field.val(URLify(values.join(' '), maxLength));
+                    field = $(field);
+                    if (field.val().length > 0) {
+                        values.push(field.val());
+                    }
+                });
+                prepopulatedField.val(URLify(values.join(' '), maxLength));
             };
 
-            $(dependencies.join(',')).keyup(populate).change(populate).focus(populate);
+            prepopulatedField.data('_changed', false);
+            prepopulatedField.change(function() {
+                prepopulatedField.data('_changed', true);
+            });
+
+            if (!prepopulatedField.val()) {
+                $(dependencies.join(',')).keyup(populate).change(populate).focus(populate);
+            }
         });
     };
 })(django.jQuery);

django/contrib/admin/static/admin/js/prepopulate.min.js

@@ -1 +1 @@
-(function(a){a.fn.prepopulate=function(d,g){return this.each(function(){var b=a(this);b.data("_changed",false);b.change(function(){b.data("_changed",true)});var c=function(){if(b.data("_changed")!=true){var e=[];a.each(d,function(h,f){a(f).val().length>0&&e.push(a(f).val())});b.val(URLify(e.join(" "),g))}};a(d.join(",")).keyup(c).change(c).focus(c)})}})(django.jQuery);
+(function(b){b.fn.prepopulate=function(e,g){return this.each(function(){var a=b(this),d=function(){if(!a.data("_changed")){var f=[];b.each(e,function(h,c){c=b(c);c.val().length>0&&f.push(c.val())});a.val(URLify(f.join(" "),g))}};a.data("_changed",false);a.change(function(){a.data("_changed",true)});a.val()||b(e.join(",")).keyup(d).change(d).focus(d)})}})(django.jQuery);

django/contrib/admin/templatetags/admin_modify.py

@@ -9,7 +9,7 @@ def prepopulated_fields_js(context):
     the prepopulated fields for both the admin form and inlines.
     """
     prepopulated_fields = []
-    if context['add'] and 'adminform' in context:
+    if 'adminform' in context:
         prepopulated_fields.extend(context['adminform'].prepopulated_fields)
     if 'inline_admin_formsets' in context:
         for inline_admin_formset in context['inline_admin_formsets']:

tests/admin_views/models.py

@@ -644,8 +644,8 @@ class MainPrepopulated(models.Model):
         max_length=20,
         choices=(('option one', 'Option One'),
                  ('option two', 'Option Two')))
-    slug1 = models.SlugField()
-    slug2 = models.SlugField()
+    slug1 = models.SlugField(blank=True)
+    slug2 = models.SlugField(blank=True)
 
 class RelatedPrepopulated(models.Model):
     parent = models.ForeignKey(MainPrepopulated)

tests/admin_views/tests.py

@@ -3438,6 +3438,50 @@ class SeleniumAdminViewsFirefoxTests(AdminSeleniumWebDriverTestCase):
             slug2='option-one-tabular-inline-ignored-characters',
         )
 
+    def test_populate_existing_object(self):
+        """
+        Ensure that the prepopulation works for existing objects too, as long
+        as the original field is empty.
+        Refs #19082.
+        """
+        # Slugs are empty to start with.
+        item = MainPrepopulated.objects.create(
+            name=' this is the mAin nÀMë',
+            pubdate='2012-02-18',
+            status='option two',
+            slug1='',
+            slug2='',
+        )
+        self.admin_login(username='super',
+                         password='secret',
+                         login_url='/test_admin/admin/')
+
+        object_url = '%s%s' % (
+            self.live_server_url,
+            '/test_admin/admin/admin_views/mainprepopulated/{}/'.format(item.id))
+
+        self.selenium.get(object_url)
+        self.selenium.find_element_by_css_selector('#id_name').send_keys(' the best')
+
+        # The slugs got prepopulated since they were originally empty
+        slug1 = self.selenium.find_element_by_css_selector('#id_slug1').get_attribute('value')
+        slug2 = self.selenium.find_element_by_css_selector('#id_slug2').get_attribute('value')
+        self.assertEqual(slug1, 'main-name-best-2012-02-18')
+        self.assertEqual(slug2, 'option-two-main-name-best')
+
+        # Save the object
+        self.selenium.find_element_by_xpath('//input[@value="Save"]').click()
+        self.wait_page_loaded()
+
+        self.selenium.get(object_url)
+        self.selenium.find_element_by_css_selector('#id_name').send_keys(' hello')
+
+        # The slugs got prepopulated didn't change since they were originally not empty
+        slug1 = self.selenium.find_element_by_css_selector('#id_slug1').get_attribute('value')
+        slug2 = self.selenium.find_element_by_css_selector('#id_slug2').get_attribute('value')
+        self.assertEqual(slug1, 'main-name-best-2012-02-18')
+        self.assertEqual(slug2, 'option-two-main-name-best')
+
     def test_collapsible_fieldset(self):
         """
         Test that the 'collapse' class in fieldsets definition allows to