Add BaseSetting.for_request() to facilitate efficient repeat access of settings when accessed before rendering

wagtail/contrib/settings/context_processors.py

@@ -9,24 +9,26 @@ class SettingsProxy(dict):
     """
     Get a SettingModuleProxy for an app using proxy['app_label']
     """
-    def __init__(self, site):
-        self.site = site
+
+    def __init__(self, request_or_site):
+        self.request_or_site = request_or_site
 
     def __missing__(self, app_label):
-        self[app_label] = value = SettingModuleProxy(self.site, app_label)
+        self[app_label] = value = SettingModuleProxy(self.request_or_site, app_label)
         return value
 
     def __str__(self):
-        return 'SettingsProxy'
+        return "SettingsProxy"
 
 
 class SettingModuleProxy(dict):
     """
     Get a setting instance using proxy['modelname']
     """
-    def __init__(self, site, app_label):
-        self.site = site
+
+    def __init__(self, request_or_site, app_label):
         self.app_label = app_label
+        self.request_or_site = request_or_site
 
     def __getitem__(self, model_name):
         """ Get a setting instance for a model """
@@ -46,19 +48,14 @@ class SettingModuleProxy(dict):
         if Model is None:
             return None
 
-        return Model.for_site(self.site)
+        if isinstance(self.request_or_site, Site):
+            return Model.for_site(self.request_or_site)
+        # Utilises cached value on request if set
+        return Model.for_request(self.request_or_site)
 
     def __str__(self):
         return 'SettingsModuleProxy({0})'.format(self.app_label)
 
 
 def settings(request):
-    def _inner(request):
-        site = Site.find_for_request(request)
-        if site is None:
-            # find_for_request() can't determine the site
-            return {}
-        else:
-            return SettingsProxy(site)
-
-    return {'settings': SimpleLazyObject(lambda: _inner(request))}
+    return {"settings": SettingsProxy(request)}

wagtail/contrib/settings/models.py

@@ -22,7 +22,31 @@ class BaseSetting(models.Model):
     @classmethod
     def for_site(cls, site):
         """
-        Get an instance of this setting for the site.
+        Get or create an instance of this setting for the site.
         """
         instance, created = cls.objects.get_or_create(site=site)
         return instance
+
+    @classmethod
+    def for_request(cls, request):
+        """
+        Get or create an instance of this model for the request,
+        and cache the result on the request for faster repeat access.
+        """
+        attr_name = cls.get_cache_attr_name()
+        if hasattr(request, attr_name):
+            return getattr(request, attr_name)
+        site = Site.find_for_request(request)
+        site_settings = cls.for_site(site)
+        setattr(request, attr_name, site_settings)
+        return site_settings
+
+    @classmethod
+    def get_cache_attr_name(cls):
+        """
+        Returns the name of the attribute that should be used to store
+        a reference to the fetched/created object on a request.
+        """
+        return "_{}.{}".format(
+            cls._meta.app_label, cls._meta.model_name
+        ).lower()