Fixed #8261 -- ModelAdmin hook for customising the "show on site" button

``ModelAdmin.view_on_site`` defines wether to show a link to the object on the
admin detail page. If ``True``, cleverness (i.e. ``Model.get_absolute_url``) is
used to get the url. If it's a callable, the callable is called with the object
as the only parameter. If ``False``, not link is displayed.

With the aim of maitaining backwards compatibility, ``True`` is the default.

6 files changed, 30 insertions, 7 deletions

diff --git a/django/contrib/admin/helpers.py b/django/contrib/admin/helpers.py
index 622664fc6b..5bc19872e9 100644
--- a/django/contrib/admin/helpers.py
+++ b/django/contrib/admin/helpers.py
@@ -202,9 +202,10 @@ class InlineAdminFormSet(object):
 
     def __iter__(self):
         for form, original in zip(self.formset.initial_forms, self.formset.get_queryset()):
+            view_on_site_url = self.opts.get_view_on_site_url(original)
             yield InlineAdminForm(self.formset, form, self.fieldsets,
                 self.prepopulated_fields, original, self.readonly_fields,
-                model_admin=self.opts)
+                model_admin=self.opts, view_on_site_url=view_on_site_url)
         for form in self.formset.extra_forms:
             yield InlineAdminForm(self.formset, form, self.fieldsets,
                 self.prepopulated_fields, None, self.readonly_fields,
@@ -242,13 +243,14 @@ class InlineAdminForm(AdminForm):
     A wrapper around an inline form for use in the admin system.
     """
     def __init__(self, formset, form, fieldsets, prepopulated_fields, original,
-      readonly_fields=None, model_admin=None):
+      readonly_fields=None, model_admin=None, view_on_site_url=None):
         self.formset = formset
         self.model_admin = model_admin
         self.original = original
         if original is not None:
             self.original_content_type_id = ContentType.objects.get_for_model(original).pk
-        self.show_url = original and hasattr(original, 'get_absolute_url')
+        self.show_url = original and view_on_site_url is not None
+        self.absolute_url = view_on_site_url
         super(InlineAdminForm, self).__init__(form, fieldsets, prepopulated_fields,
             readonly_fields, model_admin)
 
diff --git a/django/contrib/admin/options.py b/django/contrib/admin/options.py
index fe5b5e0edf..e3514dd82a 100644
--- a/django/contrib/admin/options.py
+++ b/django/contrib/admin/options.py
@@ -98,6 +98,7 @@ class BaseModelAdmin(six.with_metaclass(RenameBaseModelAdminMethods)):
     formfield_overrides = {}
     readonly_fields = ()
     ordering = None
+    view_on_site = True
 
     # validation
     validator_class = validation.BaseValidator
@@ -243,6 +244,19 @@ class BaseModelAdmin(six.with_metaclass(RenameBaseModelAdminMethods)):
 
         return db_field.formfield(**kwargs)
 
+    def get_view_on_site_url(self, obj=None):
+        if obj is None or not self.view_on_site:
+            return None
+
+        if callable(self.view_on_site):
+            return self.view_on_site(obj)
+        elif self.view_on_site:
+            # use the ContentType lookup if view_on_site is True
+            return reverse('admin:view_on_site', kwargs={
+                'content_type_id': ContentType.objects.get_for_model(obj).pk,
+                'object_id': obj.pk
+            })
+
     @property
     def declared_fieldsets(self):
         warnings.warn(
@@ -971,6 +985,7 @@ class ModelAdmin(BaseModelAdmin):
         app_label = opts.app_label
         preserved_filters = self.get_preserved_filters(request)
         form_url = add_preserved_filters({'preserved_filters': preserved_filters, 'opts': opts}, form_url)
+        view_on_site_url = self.get_view_on_site_url(obj)
         context.update({
             'add': add,
             'change': change,
@@ -978,7 +993,8 @@ class ModelAdmin(BaseModelAdmin):
             'has_change_permission': self.has_change_permission(request, obj),
             'has_delete_permission': self.has_delete_permission(request, obj),
             'has_file_field': True,  # FIXME - this should check if form or formsets have a FileField,
-            'has_absolute_url': hasattr(self.model, 'get_absolute_url'),
+            'has_absolute_url': view_on_site_url is not None,
+            'absolute_url': view_on_site_url,
             'form_url': form_url,
             'opts': opts,
             'content_type_id': ContentType.objects.get_for_model(self.model).id,
diff --git a/django/contrib/admin/templates/admin/change_form.html b/django/contrib/admin/templates/admin/change_form.html
index 1acfcd37db..79ea73933c 100644
--- a/django/contrib/admin/templates/admin/change_form.html
+++ b/django/contrib/admin/templates/admin/change_form.html
@@ -32,7 +32,7 @@
         {% url opts|admin_urlname:'history' original.pk|admin_urlquote as history_url %}
         <a href="{% add_preserved_filters history_url %}" class="historylink">{% trans "History" %}</a>
     </li>
-    {% if has_absolute_url %}<li><a href="{% url 'admin:view_on_site' content_type_id original.pk %}" class="viewsitelink">{% trans "View on site" %}</a></li>{% endif%}
+    {% if has_absolute_url %}<li><a href="{{ absolute_url }}" class="viewsitelink">{% trans "View on site" %}</a></li>{% endif%}
     {% endblock %}
   </ul>
 {% endif %}{% endif %}
diff --git a/django/contrib/admin/templates/admin/edit_inline/stacked.html b/django/contrib/admin/templates/admin/edit_inline/stacked.html
index 42f68f3f97..0fa81ef597 100644
--- a/django/contrib/admin/templates/admin/edit_inline/stacked.html
+++ b/django/contrib/admin/templates/admin/edit_inline/stacked.html
@@ -6,7 +6,7 @@
 
 {% for inline_admin_form in inline_admin_formset %}<div class="inline-related{% if forloop.last %} empty-form last-related{% endif %}" id="{{ inline_admin_formset.formset.prefix }}-{% if not forloop.last %}{{ forloop.counter0 }}{% else %}empty{% endif %}">
   <h3><b>{{ inline_admin_formset.opts.verbose_name|capfirst }}:</b>&nbsp;<span class="inline_label">{% if inline_admin_form.original %}{{ inline_admin_form.original }}{% else %}#{{ forloop.counter }}{% endif %}</span>
-    {% if inline_admin_form.show_url %}<a href="{% url 'admin:view_on_site' inline_admin_form.original_content_type_id inline_admin_form.original.pk %}">{% trans "View on site" %}</a>{% endif %}
+      {% if inline_admin_form.show_url %}<a href="{{ inline_admin_form.absolute_url }}">{% trans "View on site" %}</a>{% endif %}
     {% if inline_admin_formset.formset.can_delete and inline_admin_form.original %}<span class="delete">{{ inline_admin_form.deletion_field.field }} {{ inline_admin_form.deletion_field.label_tag }}</span>{% endif %}
   </h3>
   {% if inline_admin_form.form.non_field_errors %}{{ inline_admin_form.form.non_field_errors }}{% endif %}
diff --git a/django/contrib/admin/templates/admin/edit_inline/tabular.html b/django/contrib/admin/templates/admin/edit_inline/tabular.html
index 94be6f89b9..2a3463280d 100644
--- a/django/contrib/admin/templates/admin/edit_inline/tabular.html
+++ b/django/contrib/admin/templates/admin/edit_inline/tabular.html
@@ -27,7 +27,7 @@
         <td class="original">
           {% if inline_admin_form.original or inline_admin_form.show_url %}<p>
           {% if inline_admin_form.original %} {{ inline_admin_form.original }}{% endif %}
-          {% if inline_admin_form.show_url %}<a href="{% url 'admin:view_on_site' inline_admin_form.original_content_type_id inline_admin_form.original.pk %}">{% trans "View on site" %}</a>{% endif %}
+          {% if inline_admin_form.show_url %}<a href="{{ inline_admin_form.absolute_url }}">{% trans "View on site" %}</a>{% endif %}
             </p>{% endif %}
           {% if inline_admin_form.needs_explicit_pk_field %}{{ inline_admin_form.pk_field.field }}{% endif %}
           {{ inline_admin_form.fk_field.field }}
diff --git a/django/contrib/admin/validation.py b/django/contrib/admin/validation.py
index 84f8b67e4d..0023d13f3b 100644
--- a/django/contrib/admin/validation.py
+++ b/django/contrib/admin/validation.py
@@ -164,6 +164,11 @@ class BaseValidator(object):
                 for idx, f in enumerate(val):
                     get_field(cls, model, "prepopulated_fields['%s'][%d]" % (field, idx), f)
 
+    def validate_view_on_site_url(self, cls, model):
+        if hasattr(cls, 'view_on_site'):
+            if not callable(cls.view_on_site) and not isinstance(cls.view_on_site, bool):
+                raise ImproperlyConfigured("%s.view_on_site is not a callable or a boolean value." % cls.__name__)
+
     def validate_ordering(self, cls, model):
         " Validate that ordering refers to existing fields or is random. "
         # ordering = None