Fix caplog with logger.propagate=False

pytorch_lightning/__init__.py

@@ -1,7 +1,6 @@
 """Root package info."""
 
 import logging
-import os
 
 from pytorch_lightning.__about__ import *  # noqa: F401, F403
 
@@ -14,9 +13,6 @@
     _logger.addHandler(logging.StreamHandler())
     _logger.propagate = False
 
-_PACKAGE_ROOT = os.path.dirname(__file__)
-_PROJECT_ROOT = os.path.dirname(_PACKAGE_ROOT)
-
 from pytorch_lightning.callbacks import Callback  # noqa: E402
 from pytorch_lightning.core import LightningDataModule, LightningModule  # noqa: E402
 from pytorch_lightning.trainer import Trainer  # noqa: E402

tests/conftest.py

@@ -99,6 +99,21 @@ def reset_deterministic_algorithm():
         torch.set_deterministic(False)
 
 
+@pytest.fixture
+def caplog(caplog):
+    """Workaround for https://github.com/pytest-dev/pytest/issues/3697.
+
+    Setting ``filterwarnings`` with pytest breaks ``caplog`` when ``not logger.propagate``.
+    """
+    import logging
+
+    lightning_logger = logging.getLogger("pytorch_lightning")
+    propagate = lightning_logger.propagate
+    lightning_logger.propagate = True
+    yield caplog
+    lightning_logger.propagate = propagate
+
+
 @pytest.fixture
 def tmpdir_server(tmpdir):
     if sys.version_info >= (3, 7):

tests/utilities/test_warnings.py

@@ -50,3 +50,30 @@
 
     assert "test_warnings.py:39: UserWarning: test6" in output
     assert "test_warnings.py:40: LightningDeprecationWarning: test7" in output
+
+    # check that logging is properly configured
+    import logging
+
+    root_logger = logging.getLogger()
+    lightning_logger = logging.getLogger("pytorch_lightning")
+    # should have a `StreamHandler`
+    assert lightning_logger.hasHandlers() and len(lightning_logger.handlers) == 1
+    # set our own stream for testing
+    handler = lightning_logger.handlers[0]
+    assert isinstance(handler, logging.StreamHandler)
+    stderr = StringIO()
+    # necessary with `propagate = False`
+    lightning_logger.handlers[0].stream = stderr
+
+    # necessary with `propagate = True`
+    with redirect_stderr(stderr):
+        # Lightning should not configure the root `logging` logger by default
+        logging.info("test1")
+        root_logger.info("test1")
+        # but our logger instance
+        lightning_logger.info("test2")
+        # level is set to INFO
+        lightning_logger.debug("test3")
+
+    output = stderr.getvalue()
+    assert output == "test2\n", repr(output)