Add lock to pure python's field decoders

Fix data race that may increase flake rate of some tests.

PiperOrigin-RevId: 562044867

python/google/protobuf/internal/python_message.py

@@ -328,8 +328,8 @@ def _MaybeAddEncoder(cls, field_descriptor):
     sizer = type_checkers.TYPE_TO_SIZER[field_descriptor.type](
         field_descriptor.number, is_repeated, is_packed)
 
-  field_descriptor._encoder = field_encoder
   field_descriptor._sizer = sizer
+  field_descriptor._encoder = field_encoder
 
 
 def _MaybeAddDecoder(cls, field_descriptor):
@@ -338,7 +338,7 @@ def _MaybeAddDecoder(cls, field_descriptor):
 
   is_repeated = field_descriptor.label == _FieldDescriptor.LABEL_REPEATED
   is_map_entry = _IsMapField(field_descriptor)
-  field_descriptor._decoders = {}
+  helper_decoders = {}
 
   def AddDecoder(is_packed):
     decode_type = field_descriptor.type
@@ -372,7 +372,7 @@ def _MaybeAddDecoder(cls, field_descriptor):
           field_descriptor, field_descriptor._default_constructor,
           not field_descriptor.has_presence)
 
-    field_descriptor._decoders[is_packed] = field_decoder
+    helper_decoders[is_packed] = field_decoder
 
   AddDecoder(False)
 
@@ -381,6 +381,8 @@ def _MaybeAddDecoder(cls, field_descriptor):
     # packed values regardless of the field's options.
     AddDecoder(True)
 
+  field_descriptor._decoders = helper_decoders
+
 
 def _AddClassAttributesForNestedExtensions(descriptor, dictionary):
   extensions = descriptor.extensions_by_name

python/google/protobuf/internal/thread_safe_test.py

@@ -0,0 +1,78 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+# https://developers.google.com/protocol-buffers/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Unittest for thread safe"""
+
+import threading
+import time
+import unittest
+
+from google.protobuf import unittest_pb2
+
+
+class ThreadSafeTest(unittest.TestCase):
+
+  def setUp(self):
+    self.success = 0
+
+  def testFieldDecodersDataRace(self):
+    msg = unittest_pb2.TestAllTypes(optional_int32=1)
+    serialized_data = msg.SerializeToString()
+    lock = threading.Lock()
+
+    def ParseMessage():
+      parsed_msg = unittest_pb2.TestAllTypes()
+      time.sleep(0.005)
+      parsed_msg.ParseFromString(serialized_data)
+      with lock:
+        if msg == parsed_msg:
+          self.success += 1
+
+    field_des = unittest_pb2.TestAllTypes.DESCRIPTOR.fields_by_name[
+        'optional_int32'
+    ]
+    count = 5000
+    for x in range(0, count):
+      # delete the _decoders because only the first time parse the field
+      # may cause data race.
+      if hasattr(field_des, '_decoders'):
+        delattr(field_des, '_decoders')
+      thread1 = threading.Thread(target=ParseMessage)
+      thread2 = threading.Thread(target=ParseMessage)
+      thread1.start()
+      thread2.start()
+      thread1.join()
+      thread2.join()
+
+    self.assertEqual(count * 2, self.success)
+
+
+if __name__ == '__main__':
+  unittest.main()