gh-90195: Unset logger disabled flag when configuring it. (GH-96530)

Lib/logging/config.py

@@ -869,6 +869,7 @@ class DictConfigurator(BaseConfigurator):
         """Configure a non-root logger from a dictionary."""
         logger = logging.getLogger(name)
         self.common_logger_config(logger, config, incremental)
+        logger.disabled = False
         propagate = config.get('propagate', None)
         if propagate is not None:
             logger.propagate = propagate

Lib/test/test_logging.py

@@ -3677,6 +3677,35 @@ class ConfigDictTest(BaseTest):
             msg = str(ctx.exception)
             self.assertEqual(msg, "Unable to configure handler 'ah'")
 
+    def test_90195(self):
+        # See gh-90195
+        config = {
+            'version': 1,
+            'disable_existing_loggers': False,
+            'handlers': {
+                'console': {
+                    'level': 'DEBUG',
+                    'class': 'logging.StreamHandler',
+                },
+            },
+            'loggers': {
+                'a': {
+                    'level': 'DEBUG',
+                    'handlers': ['console']
+                }
+            }
+        }
+        logger = logging.getLogger('a')
+        self.assertFalse(logger.disabled)
+        self.apply_config(config)
+        self.assertFalse(logger.disabled)
+        # Should disable all loggers ...
+        self.apply_config({'version': 1})
+        self.assertTrue(logger.disabled)
+        del config['disable_existing_loggers']
+        self.apply_config(config)
+        # Logger should be enabled, since explicitly mentioned
+        self.assertFalse(logger.disabled)
 
 class ManagerTest(BaseTest):
     def test_manager_loggerclass(self):