Don't return the wrong cached value if parameters happen to be prefixes

johnny/cache.py

@@ -176,24 +176,44 @@ def gen_multi_key(self, values, db='default'):
             db = db[0:68] + self.gen_key(db[68:])
         return '%s_%s_multi_%s' % (self.prefix, db, self.gen_key(*values))
 
+    @staticmethod
+    def _add_separator(iterable, separator):
+        """Given an iterable, return a generator where every value is
+        separated by the separator given.
+
+        >>> list(KeyGen._add_separator([1, 2, 3], 0))
+        [1, 0, 2, 0, 3]
+
+        """
+        it = iter(iterable)
+        yield next(it)
+        for item in it:
+            yield separator
+            yield item
+
     @staticmethod
     def _convert(x):
         if isinstance(x, unicode):
             return x.encode('utf-8')
         return str(x)
 
     @staticmethod
-    def _recursive_convert(x, key):
-        for item in x:
+    def _flatten(nested_list):
+        """Return a generator where nested lists or tuples are flattened."""
+        for item in nested_list:
             if isinstance(item, (tuple, list)):
-                KeyGen._recursive_convert(item, key)
+                for subitem in KeyGen._flatten(item):
+                    yield subitem
             else:
-                key.update(KeyGen._convert(item))
+                yield item
 
     def gen_key(self, *values):
         """Generate a key from one or more values."""
         key = md5()
-        KeyGen._recursive_convert(values, key)
+
+        for item in KeyGen._add_separator(KeyGen._flatten(values), "S"):
+            key.update(KeyGen._convert(item))
+
         return key.hexdigest()
 
 

johnny/tests/cache.py

@@ -23,7 +23,9 @@ def any(iterable):
         return False
 
 # put tests in here to be included in the testing suite
-__all__ = ['MultiDbTest', 'SingleModelTest', 'MultiModelTest', 'TransactionSupportTest', 'BlackListTest', 'TransactionManagerTestCase']
+__all__ = ['MultiDbTest', 'SingleModelTest', 'MultiModelTest',
+           'TransactionSupportTest', 'BlackListTest',
+           'TransactionManagerTestCase', 'PrefixParamsTestCase']
 
 def _pre_setup(self):
     self.saved_DISABLE_SETTING = getattr(johnny_settings, 'DISABLE_QUERYSET_CACHE', False)
@@ -961,3 +963,20 @@ def test_savepoint_localstore_flush(self):
         tm._commit_all_savepoints()
         # And this checks if it actually happened.
         self.failUnless(table_key in tm.local)
+
+
+class PrefixParamsTestCase(QueryCacheBase):
+    def test_params_prefixes(self):
+        """Ensure we don't return incorrect results when queryset parameters
+        happen to concatenate to the correct value.
+
+        """
+        from testapp.models import User
+
+        User.objects.create(first_name="foo", last_name="bar")
+        User.objects.create(first_name="foob", last_name="ar")
+
+        u1 = User.objects.get(first_name="foo", last_name="bar")
+        u2 = User.objects.get(first_name="foob", last_name="ar")
+
+        self.assertNotEqual(u1, u2)