Fix the case where logger=None is passed to Trainer

CHANGELOG.md

@@ -776,6 +776,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed to avoid common hook warning if no hook is overridden ([#12131](https://github.com/PyTorchLightning/pytorch-lightning/pull/12131))
 
 
+- Fixed the case where logger=None is passed to the Trainer ([#12249](https://github.com/PyTorchLightning/pytorch-lightning/pull/12249))
+
+
 ## [1.5.10] - 2022-02-08
 
 ### Fixed

pytorch_lightning/trainer/connectors/logger_connector/logger_connector.py

@@ -84,13 +84,14 @@ def should_update_logs(self) -> bool:
         return should_log or self.trainer.should_stop
 
     def configure_logger(self, logger: Union[bool, LightningLoggerBase, Iterable[LightningLoggerBase]]) -> None:
-        if isinstance(logger, bool):
+        if not logger:
+            # logger is None or logger is False
+            self.trainer.loggers = []
+        elif logger is True:
             # default logger
-            self.trainer.loggers = (
-                [TensorBoardLogger(save_dir=self.trainer.default_root_dir, version=SLURMEnvironment.job_id())]
-                if logger
-                else []
-            )
+            self.trainer.loggers = [
+                TensorBoardLogger(save_dir=self.trainer.default_root_dir, version=SLURMEnvironment.job_id())
+            ]
         elif isinstance(logger, Iterable):
             self.trainer.loggers = list(logger)
         else:

tests/trainer/properties/test_loggers.py

@@ -35,12 +35,6 @@ def test_trainer_loggers_property():
     assert trainer.logger == logger1
     assert trainer.loggers == [logger1]
 
-    # trainer.loggers should be an empty list
-    trainer = Trainer(logger=False)
-
-    assert trainer.logger is None
-    assert trainer.loggers == []
-
     # trainer.loggers should be a list of size 1 holding the default logger
     trainer = Trainer(logger=True)
 
@@ -95,3 +89,23 @@ def test_trainer_loggers_setters():
     trainer.loggers = None
     assert trainer.loggers == []
     assert trainer.logger is None
+
+
+@pytest.mark.parametrize(
+    "logger_value",
+    [
+        None,
+        False,
+        [],
+    ],
+)
+def test_no_logger(tmpdir, logger_value):
+    """Test the cases where logger=None, logger=False, logger=[] are passed to Trainer."""
+    trainer = Trainer(
+        logger=logger_value,
+        default_root_dir=tmpdir,
+        max_steps=1,
+    )
+    assert trainer.logger is None
+    assert trainer.loggers == []
+    assert trainer.log_dir == tmpdir