Automatically use cached form data

atst/utils/form_cache.py

@@ -1,6 +1,6 @@
 from hashlib import sha256
 import json
-from werkzeug.datastructures import ImmutableMultiDict
+from werkzeug.datastructures import MultiDict
 
 
 DEFAULT_CACHE_NAME = "formcache"
@@ -16,10 +16,11 @@ class FormCache(object):
         cache_key = http_request.args.get(self.PARAM_NAME)
         if cache_key:
             return self.read(cache_key)
+        return MultiDict()
 
     def write(self, formdata, expiry_seconds=3600, key_prefix=DEFAULT_CACHE_NAME):
         value = json.dumps(formdata)
-        hash_ = sha256().hexdigest()
+        hash_ = self._hash()
         self.redis.setex(
             name=self._key(key_prefix, hash_), value=value, time=expiry_seconds
         )
@@ -28,8 +29,12 @@ class FormCache(object):
     def read(self, formdata_key, key_prefix=DEFAULT_CACHE_NAME):
         data = self.redis.get(self._key(key_prefix, formdata_key))
         dict_data = json.loads(data) if data is not None else {}
-        return ImmutableMultiDict(dict_data)
+        return MultiDict(dict_data)
 
     @staticmethod
     def _key(prefix, hash_):
         return "{}:{}".format(prefix, hash_)
+
+    @staticmethod
+    def _hash():
+        return sha256().hexdigest()