Merge branch 'release/4.3.7' into master

CONTRIBUTORS.rst

@@ -13,3 +13,4 @@ Dependency Injector Contributors
 + Bruno P. Kinoshita (kinow)
 + RobinsonMa (RobinsonMa)
 + Rüdiger Busche (JarnoRFB)
++ Dmitry Rassoshenko (rda-dev)

docs/main/changelog.rst

@@ -7,6 +7,12 @@ that were made in every particular version.
 From version 0.7.6 *Dependency Injector* framework strictly 
 follows `Semantic versioning`_
 
+4.3.7
+-----
+- Fix race in ``ThreadSafeSingleton``. Many thanks to
+  `Dmitry Rassoshenko aka rda-dev <https://github.com/rda-dev>`_ for the pull request
+  (See PR `#322 <https://github.com/ets-labs/python-dependency-injector/pull/322>`_).
+
 4.3.6
 -----
 - Fix changelog typo.

src/dependency_injector/__init__.py

@@ -1,6 +1,6 @@
 """Top-level package."""
 
-__version__ = '4.3.6'
+__version__ = '4.3.7'
 """Version number.
 
 :type: str

src/dependency_injector/providers.pyx

@@ -2178,15 +2178,19 @@ cdef class ThreadSafeSingleton(BaseSingleton):
 
         :rtype: None
         """
+        with self.__storage_lock:
             self.__storage = None
 
     cpdef object _provide(self, tuple args, dict kwargs):
         """Return single instance."""
+        storage = self.__storage
+        if storage is None:
             with self.__storage_lock:
                 if self.__storage is None:
                     self.__storage = __factory_call(self.__instantiator,
                                                     args, kwargs)
-        return self.__storage
+                storage = self.__storage
+        return storage
 
 
 cdef class DelegatedThreadSafeSingleton(ThreadSafeSingleton):