Preserve function signatures within decorated functions

The ``decorator`` module is now used when creating function decorators
within :meth:`.CacheRegion.cache_on_arguments` and
:meth:`.CacheRegion.cache_multi_on_arguments` so that function signatures
are preserved.  Pull request courtesy ankitpatel96.

Additionally adds a small performance enhancement which is to avoid
internally creating a ``@wraps()`` decorator for the creator function on
every get operation, by allowing the arguments to the creator be passed
separately to :meth:`.CacheRegion.get_or_create`.

Co-authored-by: Mike Bayer <mike_mp@zzzcomputing.com>
Fixes: #137
Change-Id: Id1008da596445770cfbf19402d38169aa60678b0
Pull-request: https://github.com/sqlalchemy/dogpile.cache/pull/136

1 files changed, 24 insertions, 0 deletions

diff --git a/tests/cache/test_decorator.py b/tests/cache/test_decorator.py
index 01d7bf4..d82b1e8 100644
--- a/tests/cache/test_decorator.py
+++ b/tests/cache/test_decorator.py
@@ -586,3 +586,27 @@ class CacheDecoratorTest(_GenericBackendFixture, TestCase):
 
         generate.set({7: 18, 10: 15})
         eq_(generate(2, 7, 10), ['2 5', 18, 15])
+
+    def test_cache_preserve_sig(self):
+        reg = self._region()
+
+        def func(a, b, c=True, *args, **kwargs):
+            return None
+
+        signature = compat.inspect_getargspec(func)
+        cached_func = reg.cache_on_arguments()(func)
+        cached_signature = compat.inspect_getargspec(cached_func)
+
+        self.assertEqual(signature, cached_signature)
+
+    def test_cache_multi_preserve_sig(self):
+        reg = self._region()
+
+        def func(a, b, c=True, *args, **kwargs):
+            return None, None
+
+        signature = compat.inspect_getargspec(func)
+        cached_func = reg.cache_multi_on_arguments()(func)
+        cached_signature = compat.inspect_getargspec(cached_func)
+
+        self.assertEqual(signature, cached_signature)