custom serialize and deserialize methods for meta

src/watson/models.py

@@ -70,6 +70,9 @@ class SearchEntry(models.Model):
 
     meta_encoded = models.TextField()
 
+    def _deserialize_meta(self):
+        return json.loads(self.meta_encoded)
+
     @property
     def meta(self):
         """Returns the meta information stored with the search entry."""
@@ -77,7 +80,7 @@ class SearchEntry(models.Model):
         if hasattr(self, META_CACHE_KEY):
             return getattr(self, META_CACHE_KEY)
         # Decode the meta.
-        meta_value = json.loads(self.meta_encoded)
+        meta_value = self._deserialize_meta()
         setattr(self, META_CACHE_KEY, meta_value)
         return meta_value
 

src/watson/registration.py

@@ -2,7 +2,9 @@
 
 from __future__ import unicode_literals
 
-import sys, json
+import sys
+import json
+import types
 from itertools import chain, islice
 from threading import local
 from functools import wraps
@@ -18,6 +20,8 @@ from django.db.models.query import QuerySet
 from django.db.models.signals import post_save, pre_delete
 from django.utils.encoding import force_text
 from django.utils.html import strip_tags
+from django.utils.functional import Promise
+from django.core.serializers.json import DjangoJSONEncoder
 try:
     from importlib import import_module
 except ImportError:
@@ -26,6 +30,24 @@ except ImportError:
 from watson.models import SearchEntry, has_int_pk
 
 
+class UniversalEncoder(DjangoJSONEncoder):
+    ENCODER_BY_TYPE = {
+        set: list,
+        frozenset: list,
+        types.GeneratorType: list,
+        bytes: lambda o: o.decode('utf-8', errors='replace'),
+    }
+
+    def default(self, obj):
+        encoder = self.ENCODER_BY_TYPE.get(type(obj))
+        if encoder:
+            return encoder(obj)
+        elif isinstance(obj, Promise):
+            return force_text(obj)
+        else:
+            return super(UniversalEncoder, self).default(obj)
+
+
 class SearchAdapterError(Exception):
 
     """Something went wrong with a search adapter."""
@@ -439,6 +461,10 @@ class SearchEngine(object):
             )
         return object_id_int, search_entries
 
+    def serialize_meta(self, meta_obj):
+        """serialise meta ready to be saved in "meta_encoded"."""
+        return json.dumps(meta_obj, cls=UniversalEncoder)
+
     def _update_obj_index_iter(self, obj):
         """Either updates the given object index, or yields an unsaved search entry."""
         model = obj.__class__
@@ -452,7 +478,7 @@ class SearchEngine(object):
             "description": adapter.get_description(obj),
             "content": adapter.get_content(obj),
             "url": adapter.get_url(obj),
-            "meta_encoded": json.dumps(adapter.get_meta(obj)),
+            "meta_encoded": self.serialize_meta(adapter.get_meta(obj)),
         }
         # Try to get the existing search entry.
         object_id_int, search_entries = self._get_entries_for_obj(obj)