Handle multiprocessing for named loggers. (#34)

* Use created logger for multiprocessing setup.

* Instead raise if trying to multiprocess log not using root.

* Add test.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Co-authored-by: Adam Tyson <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

fancylog/fancylog.py

@@ -292,14 +292,21 @@ def setup_logging(
     :param logger_name: If None, logger uses default logger. Otherwise,
         logger name is set to `logger_name`.
     """
-    initialise_logger(
+    logger = initialise_logger(
         filename,
         print_level=print_level,
         file_level=file_level,
         log_to_console=log_to_console,
         logger_name=logger_name,
     )
     if multiprocessing_aware:
+        if logger_name:
+            raise ValueError(
+                "`multiprocessing_aware` is not supported"
+                "with `logger_name`. Multiprocess logging"
+                "must be performed with the root logger."
+            )
+
         try:
             import multiprocessing_logging
 
@@ -316,8 +323,8 @@ def setup_logging(
                 "multiple processes."
             )
     else:
-        logging.info("Starting logging")
-        logging.info("Not logging multiple processes")
+        logger.info("Starting logging")
+        logger.info("Not logging multiple processes")
 
 
 def disable_logging():

tests/tests/test_general.py

@@ -1,5 +1,6 @@
 import logging
 
+import pytest
 from rich.logging import RichHandler
 
 import fancylog
@@ -42,6 +43,22 @@ def test_logger_name(tmp_path):
     assert logger_name in logging.root.manager.loggerDict
 
 
+def test_assert_named_logger_with_multiprocessing(tmp_path):
+    """
+    Test an error is raised if trying to use multiprocess
+    logging with a named logger.
+    """
+    with pytest.raises(ValueError) as e:
+        fancylog.start_logging(
+            tmp_path,
+            fancylog,
+            logger_name="hello_world",
+            multiprocessing_aware=True,
+        )
+
+    assert "root logger" in str(e.value)
+
+
 def test_logging_to_console(tmp_path, capsys):
     """
     Check that logs are written to stdout when