bpo-31457: Allow for nested LoggerAdapter objects

Some of the proxied methods use internal Logger state which isn't proxied,
causing failures if an adapter is applied to another adapter.

This commit fixes the issue, adds a new test for the use case.

Author: Lukasz Langa

Lib/logging/__init__.py

@@ -1739,6 +1739,27 @@ def hasHandlers(self):
         """
         return self.logger.hasHandlers()
 
+    def _log(self, level, msg, args, exc_info=None, extra=None, stack_info=False):
+        """
+        Low-level log implementation, proxied to allow nested logger adapters.
+        """
+        return self.logger._log(
+            level,
+            msg,
+            args,
+            exc_info=exc_info,
+            extra=extra,
+            stack_info=stack_info,
+        )
+
+    @property
+    def manager(self):
+        return self.logger.manager
+
+    @manager.setter
+    def set_manager(self, value):
+        self.logger.manager = value
+
     def __repr__(self):
         logger = self.logger
         level = getLevelName(logger.getEffectiveLevel())

Lib/test/test_logging.py

@@ -3986,6 +3986,17 @@ def test_has_handlers(self):
         self.assertFalse(self.logger.hasHandlers())
         self.assertFalse(self.adapter.hasHandlers())
 
+    def test_nested(self):
+        msg = 'Adapters can be nested, yo.'
+        adapter_adapter = logging.LoggerAdapter(logger=self.adapter, extra=None)
+        adapter_adapter.log(logging.CRITICAL, msg, self.recording)
+
+        self.assertEqual(len(self.recording.records), 1)
+        record = self.recording.records[0]
+        self.assertEqual(record.levelno, logging.CRITICAL)
+        self.assertEqual(record.msg, msg)
+        self.assertEqual(record.args, (self.recording,))
+
 
 class LoggerTest(BaseTest):
 

Misc/NEWS.d/next/Library/2017-09-13-13-33-39.bpo-31457.bIVBtI.rst

@@ -0,0 +1 @@
+LoggerAdapter objects can now be nested.