Move object_hook outside loads method so class can be extend and reused

flask/sessions.py

@@ -8,7 +8,6 @@
     :copyright: (c) 2015 by Armin Ronacher.
     :license: BSD, see LICENSE for more details.
 """
-
 import uuid
 import hashlib
 from base64 import b64encode, b64decode
@@ -49,22 +48,82 @@ class SessionMixin(object):
     modified = True
 
 
-def _tag(value):
+class TaggedJSONSerializer(object):
-    if isinstance(value, tuple):
+    """A customized JSON serializer that supports a few extra types that
-        return {' t': [_tag(x) for x in value]}
+    we take for granted when serializing (tuples, markup objects, datetime).
-    elif isinstance(value, uuid.UUID):
+    """
-        return {' u': value.hex}
+
-    elif isinstance(value, bytes):
+    def __init__(self):
-        return {' b': b64encode(value).decode('ascii')}
+        self.conversions = [
-    elif callable(getattr(value, '__html__', None)):
+            {
-        return {' m': text_type(value.__html__())}
+                'check': lambda value: self._is_dict_with_used_key(value),
-    elif isinstance(value, list):
+                'tag': lambda value: self._tag_dict_used_with_key(value),
-        return [_tag(x) for x in value]
+                'untag': lambda value: self._untag_dict_used_with_key(value),
-    elif isinstance(value, datetime):
+                'key': ' di',
-        return {' d': http_date(value)}
+            },
-    elif isinstance(value, dict):
+            {
-        return dict((k, _tag(v)) for k, v in iteritems(value))
+                'check': lambda value: isinstance(value, tuple),
-    elif isinstance(value, str):
+                'tag': lambda value: [self._tag(x) for x in value],
+                'untag': lambda value: tuple(value),
+                'key': ' t',
+            },
+            {
+                'check': lambda value: isinstance(value, uuid.UUID),
+                'tag': lambda value: value.hex,
+                'untag': lambda value: uuid.UUID(value),
+                'key': ' u',
+            },
+            {
+                'check': lambda value: isinstance(value, bytes),
+                'tag': lambda value: b64encode(value).decode('ascii'),
+                'untag': lambda value: b64decode(value),
+                'key': ' b',
+            },
+            {
+                'check': lambda value: callable(getattr(value, '__html__',
+                                                        None)),
+                'tag': lambda value: text_type(value.__html__()),
+                'untag': lambda value: Markup(value),
+                'key': ' m',
+            },
+            {
+                'check': lambda value: isinstance(value, list),
+                'tag': lambda value: [self._tag(x) for x in value],
+            },
+            {
+                'check': lambda value: isinstance(value, datetime),
+                'tag': lambda value: http_date(value),
+                'untag': lambda value: parse_date(value),
+                'key': ' d',
+            },
+            {
+                'check': lambda value: isinstance(value, dict),
+                'tag': lambda value: dict((k, self._tag(v)) for k, v in
+                                          iteritems(value)),
+            },
+            {
+                'check': lambda value: isinstance(value, str),
+                'tag': lambda value: self._tag_string(value),
+            }
+        ]
+
+    @property
+    def keys(self):
+        return [c['key'] for c in self.conversions if c.get('key')]
+
+    def _get_conversion_untag(self, key):
+        return next(
+            (c['untag'] for c in self.conversions if c.get('key') == key),
+            lambda v: None
+        )
+
+    def _is_dict_with_used_key(self, v):
+        return isinstance(v, dict) and len(v) == 1 and list(v)[0] in self.keys
+
+    def _was_dict_with_used_key(self, k):
+        return k.endswith('__') and k[:-2] in self.keys
+
+    def _tag_string(self, value):
         try:
             return text_type(value)
         except UnicodeError:
@@ -73,38 +132,38 @@ def _tag(value):
                 u'non-ASCII data was passed to the session system '
                 u'which can only store unicode strings.  Consider '
                 u'base64 encoding your string (String was %r)' % value)
-    return value
 
+    def _tag_dict_used_with_key(self, value):
+        k, v = next(iteritems(value))
+        return {'%s__' % k: v}
 
-class TaggedJSONSerializer(object):
+    def _tag(self, value):
-    """A customized JSON serializer that supports a few extra types that
+        for tag_ops in self.conversions:
-    we take for granted when serializing (tuples, markup objects, datetime).
+            if tag_ops['check'](value):
-    """
+                tag = tag_ops.get('key')
+                if tag:
+                    return {tag: tag_ops['tag'](value)}
+                return tag_ops['tag'](value)
+        return value
+
+    def _untag_dict_used_with_key(self, the_value):
+        k, v = next(iteritems(the_value))
+        if self._was_dict_with_used_key(k):
+            return {k[:-2]: self._untag(v)}
+
+    def _untag(self, obj):
+        if len(obj) != 1:
+            return obj
+        the_key, the_value = next(iteritems(obj))
+        untag = self._get_conversion_untag(the_key)
+        new_value = untag(the_value)
+        return new_value if new_value else obj
 
     def dumps(self, value):
-        return json.dumps(_tag(value), separators=(',', ':'))
+        return json.dumps(self._tag(value), separators=(',', ':'))
-
-    LOADS_MAP = {
-        ' t': tuple,
-        ' u': uuid.UUID,
-        ' b': b64decode,
-        ' m': Markup,
-        ' d': parse_date,
-    }
 
     def loads(self, value):
-        def object_hook(obj):
+        return json.loads(value, object_hook=self._untag)
-            if len(obj) != 1:
-                return obj
-            the_key, the_value = next(iteritems(obj))
-            # Check the key for a corresponding function
-            return_function = self.LOADS_MAP.get(the_key)
-            if return_function:
-                # Pass the value to the function
-                return return_function(the_value)
-            # Didn't find a function for this object
-            return obj
-        return json.loads(value, object_hook=object_hook)
 
 
 session_json_serializer = TaggedJSONSerializer()

tests/test_basic.py

@@ -383,6 +383,9 @@ def test_session_special_types():
         flask.session['dt'] = now
         flask.session['b'] = b'\xff'
         flask.session['t'] = (1, 2, 3)
+        flask.session['spacefirst'] = {' t': 'not-a-tuple'}
+        flask.session['withunderscores'] = {' t__': 'not-a-tuple'}
+        flask.session['notadict'] = {' di': 'not-a-dict'}
         return response
 
     @app.route('/')
@@ -399,6 +402,9 @@ def test_session_special_types():
     assert rv['b'] == b'\xff'
     assert type(rv['b']) == bytes
     assert rv['t'] == (1, 2, 3)
+    assert rv['spacefirst'] == {' t': 'not-a-tuple'}
+    assert rv['withunderscores'] == {' t__': 'not-a-tuple'}
+    assert rv['notadict'] == {' di': 'not-a-dict'}
 
 
 def test_session_cookie_setting():