From a8607785dc17ec3932210e19cb459d5877cb880b Mon Sep 17 00:00:00 2001
From: Joe Ziminski <55797454+JoeZiminski@users.noreply.github.com>
Date: Thu, 2 May 2024 11:33:03 +0100
Subject: [PATCH] Don't propagate named loggers. (#32)

* Don't propagate named loggers and add tests.

* Tidy up test docstring.

* Fix working of test name.
---
 fancylog/fancylog.py        |  1 +
 tests/tests/test_general.py | 56 ++++++++++++++++++++++++++++++++++++-
 2 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/fancylog/fancylog.py b/fancylog/fancylog.py
index 2ef48e1..156089a 100644
--- a/fancylog/fancylog.py
+++ b/fancylog/fancylog.py
@@ -244,6 +244,7 @@ def initialise_logger(
     if logger_name:
         logger = logging.getLogger(logger_name)
         logger.handlers = []
+        logger.propagate = False
     else:
         logger = logging.getLogger()
 
diff --git a/tests/tests/test_general.py b/tests/tests/test_general.py
index 3f8b623..fe78753 100644
--- a/tests/tests/test_general.py
+++ b/tests/tests/test_general.py
@@ -42,6 +42,26 @@ def test_logger_name(tmp_path):
     assert logger_name in logging.root.manager.loggerDict
 
 
+def test_logging_to_console(tmp_path, capsys):
+    """
+    Check that logs are written to stdout when
+    `log_to_console` is `True`.
+    """
+    logger_name = "hello_world"
+
+    fancylog.start_logging(
+        tmp_path, fancylog, log_to_console=True, logger_name=logger_name
+    )
+
+    logger = logging.getLogger(logger_name)
+
+    logger.debug("!!£%$")
+
+    captured = capsys.readouterr()
+
+    assert "!!£%$" in captured.out
+
+
 def test_correct_handlers_are_set(tmp_path):
     """
     Test the handlers on the logger are as specified by the
@@ -51,7 +71,7 @@ def test_correct_handlers_are_set(tmp_path):
     """
     logger_name = "hello_world"
 
-    # Test no handlers are assigned when non requested
+    # Test no handlers are assigned when not requested
     fancylog.start_logging(
         tmp_path,
         fancylog,
@@ -141,3 +161,37 @@ def test_handlers_are_refreshed(tmp_path):
     )
 
     assert logger.handlers == []
+
+
+def test_named_logger_doesnt_propagate(tmp_path, capsys):
+    """
+    By default, named loggers will propagate through
+    parent handlers. Root is always parent to named loggers.
+    This means that named logger can still print to console
+    through the root StreamHandler unless `propagate` is set
+    to `False`. Check here that propagate is set to False and
+    indeed named logger does not print to console.
+    """
+    logger_name = "hello_world"
+
+    fancylog.start_logging(
+        tmp_path, fancylog, logger_name=logger_name, log_to_console=False
+    )
+
+    logger = logging.getLogger(logger_name)
+
+    assert logger.propagate is False
+
+    logger.debug("XN$£ not in stdout")
+
+    logging.debug("YYXX in stdout")
+
+    logger.debug("PQ&* not in stdout")
+
+    captured = capsys.readouterr()
+
+    assert "XN$£" not in captured.out, "logger initially writing to stdout"
+    assert "YYXX" in captured.out, "root is not writing to stdout"
+    assert (
+        "PQ&*" not in captured.out
+    ), "logger writing to stdout through root handler"