Fixed #15089 -- Allowed contrib.sites to lookup the current site based on request.get_host().

Thanks Claude Paroz, Riccardo Magliocchetti, and Damian Moore
for contributions to the patch.

7 files changed, 100 insertions, 28 deletions

diff --git a/django/contrib/contenttypes/views.py b/django/contrib/contenttypes/views.py
index 6bc3aa04dd..02446d023a 100644
--- a/django/contrib/contenttypes/views.py
+++ b/django/contrib/contenttypes/views.py
@@ -72,7 +72,7 @@ def shortcut(request, content_type_id, object_id):
         # Fall back to the current site (if possible).
         if object_domain is None:
             try:
-                object_domain = Site.objects.get_current().domain
+                object_domain = Site.objects.get_current(request).domain
             except Site.DoesNotExist:
                 pass
 
diff --git a/django/contrib/sites/middleware.py b/django/contrib/sites/middleware.py
index eb34d2ecdb..fdc7923581 100644
--- a/django/contrib/sites/middleware.py
+++ b/django/contrib/sites/middleware.py
@@ -1,4 +1,4 @@
-from .models import Site
+from .shortcuts import get_current_site
 
 
 class CurrentSiteMiddleware(object):
@@ -7,4 +7,4 @@ class CurrentSiteMiddleware(object):
     """
 
     def process_request(self, request):
-        request.site = Site.objects.get_current()
+        request.site = get_current_site(request)
diff --git a/django/contrib/sites/models.py b/django/contrib/sites/models.py
index 0e80d9107a..9efba9bd5c 100644
--- a/django/contrib/sites/models.py
+++ b/django/contrib/sites/models.py
@@ -34,26 +34,39 @@ def _simple_domain_name_validator(value):
 
 class SiteManager(models.Manager):
 
-    def get_current(self):
+    def _get_site_by_id(self, site_id):
+        if site_id not in SITE_CACHE:
+            site = self.get(pk=site_id)
+            SITE_CACHE[site_id] = site
+        return SITE_CACHE[site_id]
+
+    def _get_site_by_request(self, request):
+        host = request.get_host()
+        if host not in SITE_CACHE:
+            site = self.get(domain__iexact=host)
+            SITE_CACHE[host] = site
+        return SITE_CACHE[host]
+
+    def get_current(self, request=None):
         """
-        Returns the current ``Site`` based on the SITE_ID in the
-        project's settings. The ``Site`` object is cached the first
-        time it's retrieved from the database.
+        Returns the current Site based on the SITE_ID in the project's settings.
+        If SITE_ID isn't defined, it returns the site with domain matching
+        request.get_host(). The ``Site`` object is cached the first time it's
+        retrieved from the database.
         """
         from django.conf import settings
-        try:
-            sid = settings.SITE_ID
-        except AttributeError:
-            raise ImproperlyConfigured(
-                "You're using the Django \"sites framework\" without having "
-                "set the SITE_ID setting. Create a site in your database and "
-                "set the SITE_ID setting to fix this error.")
-        try:
-            current_site = SITE_CACHE[sid]
-        except KeyError:
-            current_site = self.get(pk=sid)
-            SITE_CACHE[sid] = current_site
-        return current_site
+        if getattr(settings, 'SITE_ID', ''):
+            site_id = settings.SITE_ID
+            return self._get_site_by_id(site_id)
+        elif request:
+            return self._get_site_by_request(request)
+
+        raise ImproperlyConfigured(
+            "You're using the Django \"sites framework\" without having "
+            "set the SITE_ID setting. Create a site in your database and "
+            "set the SITE_ID setting or pass a request to "
+            "Site.objects.get_current() to fix this error."
+        )
 
     def clear_cache(self):
         """Clears the ``Site`` object cache."""
@@ -103,5 +116,9 @@ def clear_site_cache(sender, **kwargs):
         del SITE_CACHE[instance.pk]
     except KeyError:
         pass
+    try:
+        del SITE_CACHE[Site.objects.get(pk=instance.pk).domain]
+    except (KeyError, Site.DoesNotExist):
+        pass
 pre_save.connect(clear_site_cache, sender=Site)
 pre_delete.connect(clear_site_cache, sender=Site)
diff --git a/django/contrib/sites/shortcuts.py b/django/contrib/sites/shortcuts.py
index c525948286..12471dc9a5 100644
--- a/django/contrib/sites/shortcuts.py
+++ b/django/contrib/sites/shortcuts.py
@@ -12,7 +12,7 @@ def get_current_site(request):
     # the Site models when django.contrib.sites isn't installed.
     if apps.is_installed('django.contrib.sites'):
         from .models import Site
-        return Site.objects.get_current()
+        return Site.objects.get_current(request)
     else:
         from .requests import RequestSite
         return RequestSite(request)
diff --git a/django/contrib/sites/tests.py b/django/contrib/sites/tests.py
index fadd4aa81d..94264b4af6 100644
--- a/django/contrib/sites/tests.py
+++ b/django/contrib/sites/tests.py
@@ -5,8 +5,9 @@ from django.core.exceptions import ObjectDoesNotExist, ValidationError
 from django.http import HttpRequest
 from django.test import TestCase, modify_settings, override_settings
 
+from . import models
 from .middleware import CurrentSiteMiddleware
-from .models import Site
+from .models import clear_site_cache, Site
 from .requests import RequestSite
 from .shortcuts import get_current_site
 
@@ -15,7 +16,12 @@ from .shortcuts import get_current_site
 class SitesFrameworkTests(TestCase):
 
     def setUp(self):
-        Site(id=settings.SITE_ID, domain="example.com", name="example.com").save()
+        self.site = Site(
+            id=settings.SITE_ID,
+            domain="example.com",
+            name="example.com",
+        )
+        self.site.save()
 
     def test_save_another(self):
         # Regression for #17415
@@ -71,6 +77,17 @@ class SitesFrameworkTests(TestCase):
             self.assertIsInstance(site, RequestSite)
             self.assertEqual(site.name, "example.com")
 
+    @override_settings(SITE_ID='', ALLOWED_HOSTS=['example.com'])
+    def test_get_current_site_no_site_id(self):
+        request = HttpRequest()
+        request.META = {
+            "SERVER_NAME": "example.com",
+            "SERVER_PORT": "80",
+        }
+        del settings.SITE_ID
+        site = get_current_site(request)
+        self.assertEqual(site.name, "example.com")
+
     def test_domain_name_with_whitespaces(self):
         # Regression for #17320
         # Domain names are not allowed contain whitespace characters
@@ -81,6 +98,26 @@ class SitesFrameworkTests(TestCase):
         site.domain = "test\ntest"
         self.assertRaises(ValidationError, site.full_clean)
 
+    def test_clear_site_cache(self):
+        request = HttpRequest()
+        request.META = {
+            "SERVER_NAME": "example.com",
+            "SERVER_PORT": "80",
+        }
+        self.assertEqual(models.SITE_CACHE, {})
+        get_current_site(request)
+        expected_cache = {self.site.id: self.site}
+        self.assertEqual(models.SITE_CACHE, expected_cache)
+
+        with self.settings(SITE_ID=''):
+            get_current_site(request)
+
+        expected_cache.update({self.site.domain: self.site})
+        self.assertEqual(models.SITE_CACHE, expected_cache)
+
+        clear_site_cache(Site, instance=self.site)
+        self.assertEqual(models.SITE_CACHE, {})
+
 
 class MiddlewareTest(TestCase):
 
diff --git a/docs/ref/contrib/sites.txt b/docs/ref/contrib/sites.txt
index 7561d544a8..3400b10288 100644
--- a/docs/ref/contrib/sites.txt
+++ b/docs/ref/contrib/sites.txt
@@ -18,10 +18,6 @@ The sites framework is mainly based on a simple model:
 .. class:: models.Site
 
     A model for storing the ``domain`` and ``name`` attributes of a Web site.
-    The :setting:`SITE_ID` setting specifies the database ID of the
-    :class:`~django.contrib.sites.models.Site` object (accessible using
-    the automatically added ``id`` attribute) associated with that
-    particular settings file.
 
     .. attribute:: domain
 
@@ -31,6 +27,14 @@ The sites framework is mainly based on a simple model:
 
         A human-readable "verbose" name for the Web site.
 
+The :setting:`SITE_ID` setting specifies the database ID of the
+:class:`~django.contrib.sites.models.Site` object associated with that
+particular settings file. It the setting is omitted, the
+:func:`~django.contrib.sites.shortcuts.get_current_site` function will
+try to get the current site by comparing the
+:attr:`~django.contrib.sites.models.Site.domain` with the host name from
+the :meth:`request.get_host() <django.http.HttpRequest.get_host>` method.
+
 How you use this is up to you, but Django uses it in a couple of ways
 automatically via simple conventions.
 
@@ -308,6 +312,11 @@ model(s). It's a model :doc:`manager </topics/db/managers>` that
 automatically filters its queries to include only objects associated
 with the current :class:`~django.contrib.sites.models.Site`.
 
+.. admonition:: Mandatory :setting:`SITE_ID`
+
+    The ``CurrentSiteManager`` is only usable when the :setting:`SITE_ID`
+    setting is defined in your settings.
+
 Use :class:`~django.contrib.sites.managers.CurrentSiteManager` by adding it to
 your model explicitly. For example::
 
@@ -492,3 +501,9 @@ Finally, to avoid repetitive fallback code, the framework provides a
     .. versionchanged:: 1.7
 
       This function used to be defined in ``django.contrib.sites.models``.
+
+    .. versionchanged:: 1.8
+
+      This function will now lookup the current site based on
+      :meth:`request.get_host() <django.http.HttpRequest.get_host>` if the
+      :setting:`SITE_ID` setting is not defined.
diff --git a/docs/releases/1.8.txt b/docs/releases/1.8.txt
index beca378ac7..67a6fab91d 100644
--- a/docs/releases/1.8.txt
+++ b/docs/releases/1.8.txt
@@ -139,7 +139,10 @@ Minor features
 :mod:`django.contrib.sites`
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-* ...
+* :func:`~django.contrib.sites.shortcuts.get_current_site` will now lookup
+  the current site based on :meth:`request.get_host()
+  <django.http.HttpRequest.get_host>` if the :setting:`SITE_ID` setting is not
+  defined.
 
 :mod:`django.contrib.staticfiles`
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^