fix: preserve configured logging levels

cmdstanpy/utils/logging.py

@@ -16,8 +16,9 @@ def get_logger() -> logging.Logger:
     """cmdstanpy logger"""
     logger = logging.getLogger("cmdstanpy")
     if not logger.hasHandlers():
-        # send all messages to handlers
-        logger.setLevel(logging.DEBUG)
+        # Send all messages to handlers unless the user selected a level.
+        if logger.level == logging.NOTSET:
+            logger.setLevel(logging.DEBUG)
         # add a default handler to the logger to WARNING and higher
         handler = logging.StreamHandler()
         handler.setLevel(logging.WARNING)

docsrc/users-guide/outputs.rst

@@ -97,6 +97,16 @@ These functions also work as context managers for more local control:
         fit = model.sample(data=data_file, show_progress=False)
 
 
+An explicitly configured level is preserved when CmdStanPy initializes its
+logger. For example, to show errors but suppress warnings, set the level before
+using a model:
+
+.. code-block:: python
+
+    import logging
+
+    logging.getLogger("cmdstanpy").setLevel(logging.ERROR)
+
 For more fine-grained control, one can interact with the underlying ``logging``
 library directly. For example, the following code installs a custom handler
 that sends all logs (including the ``DEBUG`` logs, which are hidden by

test/test_logging.py

@@ -1,12 +1,45 @@
 """Logging control tests"""
 
 import logging
+import subprocess
+import sys
 
 import pytest
 
 import cmdstanpy
 
 
+@pytest.mark.parametrize(
+    "level", [logging.NOTSET, logging.DEBUG, logging.WARNING, logging.ERROR]
+)
+def test_logger_initialization_preserves_level(level: int) -> None:
+    # A fresh process avoids pytest's logging handlers and the cached logger.
+    result = subprocess.run(
+        [
+            sys.executable,
+            "-c",
+            f"""
+import logging
+import cmdstanpy
+
+logger = logging.getLogger('cmdstanpy')
+logger.setLevel({level})
+logger = cmdstanpy.utils.get_logger()
+print(logger.level)
+logger.warning('warning message')
+logger.error('error message')
+""",
+        ],
+        capture_output=True,
+        text=True,
+        check=True,
+    )
+    expected_level = logging.DEBUG if level == logging.NOTSET else level
+    assert int(result.stdout) == expected_level
+    assert ('warning message' in result.stderr) == (level <= logging.WARNING)
+    assert 'error message' in result.stderr
+
+
 def test_disable_logging(caplog: pytest.LogCaptureFixture) -> None:
     logger = cmdstanpy.utils.logging.get_logger()