bpo-37742: Return the root logger when logging.getLogger('root') is c… (#15077)

* bpo-37742: Return the root logger when logging.getLogger('root') is called.

* Added type check guard on logger name in logging.getLogger() and refined a test.

Lib/logging/__init__.py

@@ -2024,10 +2024,9 @@ def getLogger(name=None):
 
     If no name is specified, return the root logger.
     """
-    if name:
-        return Logger.manager.getLogger(name)
-    else:
+    if not name or isinstance(name, str) and name == root.name:
         return root
+    return Logger.manager.getLogger(name)
 
 def critical(msg, *args, **kwargs):
     """

Lib/test/test_logging.py

@@ -4856,6 +4856,7 @@ class LoggerTest(BaseTest):
         self.assertIs(root, logging.root)
         self.assertIs(root, logging.getLogger(None))
         self.assertIs(root, logging.getLogger(''))
+        self.assertIs(root, logging.getLogger('root'))
         self.assertIs(root, logging.getLogger('foo').root)
         self.assertIs(root, logging.getLogger('foo.bar').root)
         self.assertIs(root, logging.getLogger('foo').parent)

Misc/NEWS.d/next/Library/2019-08-02-14-01-25.bpo-37742.f4Xn9S.rst

+The logging.getLogger() API now returns the root logger when passed the name
+'root', whereas previously it returned a non-root logger named 'root'. This
+could affect cases where user code explicitly wants a non-root logger named
+'root', or instantiates a logger using logging.getLogger(__name__) in some
+top-level module called 'root.py'.