logging: Fall back to root logger level for unset child.

Previously a child logger just uses the global default when unset.
Modified to matches the CPython behavior of using the parent's level.

Also implemented CPython's getEffectiveLevel() which provides a convenient
way to implement this. In our version, we only ever have one parent
(the root), so it only has to recurse one level.

Also set the default level to WARNING to match CPython.

Updated the examples to highlight the differences (but they now match).

This work was funded through GitHub Sponsors.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

python-stdlib/logging/examples/basic_example.py

@@ -1,3 +1,7 @@
 import logging
 
-logging.warning("test")
+logging.debug("test - debug")  # ignored by default
+logging.info("test - info")  # ignored by default
+logging.warning("test - warning")
+logging.error("test - error")
+logging.critical("test - critical")

python-stdlib/logging/examples/root_logger.py

@@ -5,3 +5,4 @@ for handler in logging.getLogger().handlers:
     handler.setFormatter(logging.Formatter("[%(levelname)s]:%(name)s:%(message)s"))
 logging.info("hello upy")
 logging.getLogger("child").info("hello 2")
+logging.getLogger("child").debug("hello 2")

python-stdlib/logging/logging.py

@@ -1,15 +1,19 @@
+from micropython import const
+
 import sys
 import time
 
 if hasattr(time, "strftime"):
     from time import strftime
 
-CRITICAL = 50
-ERROR = 40
-WARNING = 30
-INFO = 20
-DEBUG = 10
-NOTSET = 0
+CRITICAL = const(50)
+ERROR = const(40)
+WARNING = const(30)
+INFO = const(20)
+DEBUG = const(10)
+NOTSET = const(0)
+
+_DEFAULT_LEVEL = const(WARNING)
 
 _level_dict = {
     CRITICAL: "CRITICAL",
@@ -22,7 +26,6 @@ _level_dict = {
 
 _loggers = {}
 _stream = sys.stderr
-_level = INFO
 _default_fmt = "%(levelname)s:%(name)s:%(message)s"
 _default_datefmt = "%Y-%m-%d %H:%M:%S"
 
@@ -115,7 +118,10 @@ class Logger:
         self.level = level
 
     def isEnabledFor(self, level):
-        return level >= (self.level or _level)
+        return level >= self.getEffectiveLevel()
+
+    def getEffectiveLevel(self):
+        return self.level or getLogger().level or _DEFAULT_LEVEL
 
     def log(self, level, msg, *args):
         if self.isEnabledFor(level):