Fix access to logger attribute when multiple loggers are used (#14234)

* Fix access to logger attribute when multiple loggers are used

Author: awaelchli

src/pytorch_lightning/CHANGELOG.md

@@ -9,7 +9,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 ### Fixed
 
 - Fixed an assertion error when using a `ReduceOnPlateau` scheduler with the Horovod strategy ([#14215](https://github.com/Lightning-AI/lightning/pull/14215))
-
+- Fixed an `AttributeError` when accessing `LightningModule.logger` and the Trainer has multiple loggers ([#14234](https://github.com/Lightning-AI/lightning/pull/14234))
 
 
 ## [1.7.2] - 2022-08-16

src/pytorch_lightning/core/module.py

@@ -19,6 +19,7 @@
 import numbers
 import os
 import tempfile
+import warnings
 import weakref
 from contextlib import contextmanager
 from pathlib import Path
@@ -39,7 +40,7 @@
 from pytorch_lightning.core.saving import ModelIO
 from pytorch_lightning.loggers import Logger, LoggerCollection
 from pytorch_lightning.trainer.connectors.logger_connector.fx_validator import _FxValidator
-from pytorch_lightning.utilities import _IS_WINDOWS, _TORCH_GREATER_EQUAL_1_10, GradClipAlgorithmType, warnings
+from pytorch_lightning.utilities import _IS_WINDOWS, _TORCH_GREATER_EQUAL_1_10, GradClipAlgorithmType
 from pytorch_lightning.utilities.apply_func import apply_to_collection, convert_to_tensors
 from pytorch_lightning.utilities.cloud_io import get_filesystem
 from pytorch_lightning.utilities.distributed import distributed_available, sync_ddp

tests/tests_pytorch/deprecated_api/test_remove_1-8.py

@@ -764,6 +764,12 @@ def test_v1_8_0_logger_collection(tmpdir):
     with pytest.deprecated_call(match="`LoggerCollection` is deprecated in v1.6"):
         _ = LoggerCollection([logger1, logger2])
 
+    model = BoringModel()
+    trainer = Trainer(logger=[logger1, logger2])
+    model.trainer = trainer
+    with pytest.deprecated_call(match="logger` will return the first logger"):
+        _ = model.logger
+
 
 def test_v1_8_0_precision_plugin_checkpoint_hooks(tmpdir):
     class PrecisionPluginSaveHook(PrecisionPlugin):