[ENG-6801] Preprint _id caching

osf/models/base.py

@@ -16,7 +16,7 @@
 
 from framework import sentry
 from osf.exceptions import ValidationError
-from osf.utils.caching import cached_property
+from osf.utils.caching import cached_property, cached_not_none_property
 from osf.utils.fields import LowercaseCharField, NonNaiveDateTimeField
 from website import settings as website_settings
 
@@ -521,9 +521,8 @@ class Meta:
 
     versioned_guids = GenericRelation('GuidVersionsThrough', related_name='referent', related_query_name='referents')
 
-    @property
+    @cached_not_none_property
     def _id(self):
-        # TODO: maybe a cached property?
         try:
             versioned_guid = self.versioned_guids
             if not versioned_guid.exists():

osf/utils/caching.py

@@ -61,6 +61,23 @@ def do_fdel(obj):
 
         return do_fdel
 
+class _CachedNotNoneProperty(_CachedProperty):
+
+    def _wrap_fget(self, fget):
+        @wraps(fget)
+        def do_fget(obj):
+            if hasattr(obj, self._cache_name):
+                if getattr(obj, self._cache_name):
+                    return getattr(obj, self._cache_name)
+            # Generate the value to cache.
+            value = fget(obj)
+            if value:
+                setattr(obj, self._cache_name, value)
+            return value
+
+        return do_fget
+
 
 # Public name for the cached property decorator. Using a class as a decorator just looks plain ugly. :P
 cached_property = _CachedProperty
+cached_not_none_property = _CachedNotNoneProperty