loggingTools: move here the LastResortLogger from py23

and add a small test

Lib/fontTools/misc/loggingTools.py

@@ -527,6 +527,67 @@ def deprecateFunction(msg, category=UserWarning):
 	return decorator
 
 
+class LastResortLogger(logging.Logger):
+	""" Adds support for 'lastResort' handler introduced in Python 3.2.
+	It allows to print messages to sys.stderr even when no explicit handler
+	was configured.
+	To enable it, you can do:
+
+		import logging
+		logging.lastResort = StderrHandler(logging.WARNING)
+		logging.setLoggerClass(LastResortLogger)
+	"""
+
+	def callHandlers(self, record):
+		# this is the same as Python 3.5's logging.Logger.callHandlers
+		c = self
+		found = 0
+		while c:
+			for hdlr in c.handlers:
+				found = found + 1
+				if record.levelno >= hdlr.level:
+					hdlr.handle(record)
+			if not c.propagate:
+				c = None  # break out
+			else:
+				c = c.parent
+		if found == 0:
+			if logging.lastResort:
+				if record.levelno >= logging.lastResort.level:
+					logging.lastResort.handle(record)
+			elif (
+				logging.raiseExceptions
+				and not self.manager.emittedNoHandlerWarning
+			):
+				sys.stderr.write(
+					"No handlers could be found for logger"
+					' "%s"\n' % self.name
+				)
+				self.manager.emittedNoHandlerWarning = True
+
+
+class StderrHandler(logging.StreamHandler):
+	""" This class is like a StreamHandler using sys.stderr, but always uses
+	whateve sys.stderr is currently set to rather than the value of
+	sys.stderr at handler construction time.
+	"""
+
+	def __init__(self, level=logging.NOTSET):
+		"""
+		Initialize the handler.
+		"""
+		logging.Handler.__init__(self, level)
+
+	@property
+	def stream(self):
+		# the try/execept avoids failures during interpreter shutdown, when
+		# globals are set to None
+		try:
+			return sys.stderr
+		except AttributeError:
+			return __import__("sys").stderr
+
+
 if __name__ == "__main__":
 	import doctest
 	sys.exit(doctest.testmod(optionflags=doctest.ELLIPSIS).failed)

Lib/fontTools/misc/py23.py

@@ -419,56 +419,6 @@ else:
 	round = round3
 
 
-import logging
-
-
-class _Logger(logging.Logger):
-	""" Add support for 'lastResort' handler introduced in Python 3.2. """
-
-	def callHandlers(self, record):
-		# this is the same as Python 3.5's logging.Logger.callHandlers
-		c = self
-		found = 0
-		while c:
-			for hdlr in c.handlers:
-				found = found + 1
-				if record.levelno >= hdlr.level:
-					hdlr.handle(record)
-			if not c.propagate:
-				c = None  # break out
-			else:
-				c = c.parent
-		if (found == 0):
-			if logging.lastResort:
-				if record.levelno >= logging.lastResort.level:
-					logging.lastResort.handle(record)
-			elif logging.raiseExceptions and not self.manager.emittedNoHandlerWarning:
-				sys.stderr.write("No handlers could be found for logger"
-								 " \"%s\"\n" % self.name)
-				self.manager.emittedNoHandlerWarning = True
-
-
-class _StderrHandler(logging.StreamHandler):
-	""" This class is like a StreamHandler using sys.stderr, but always uses
-	whatever sys.stderr is currently set to rather than the value of
-	sys.stderr at handler construction time.
-	"""
-	def __init__(self, level=logging.NOTSET):
-		"""
-		Initialize the handler.
-		"""
-		logging.Handler.__init__(self, level)
-
-	@property
-	def stream(self):
-		# the try/execept avoids failures during interpreter shutdown, when
-		# globals are set to None
-		try:
-			return sys.stderr
-		except AttributeError:
-			return __import__('sys').stderr
-
-
 try:
 	from types import SimpleNamespace
 except ImportError:

Tests/misc/loggingTools_test.py

@@ -1,11 +1,20 @@
 from __future__ import print_function, division, absolute_import
 from fontTools.misc.py23 import *
 from fontTools.misc.loggingTools import (
-    LevelFormatter, Timer, configLogger, ChannelsFilter, LogMixin)
+    LevelFormatter,
+    Timer,
+    configLogger,
+    ChannelsFilter,
+    LogMixin,
+    StderrHandler,
+    LastResortLogger,
+    _resetExistingLoggers,
+)
 import logging
 import textwrap
 import time
 import re
+import sys
 import pytest
 
 
@@ -170,3 +179,32 @@ def test_LogMixin():
     assert isinstance(b.log, logging.Logger)
     assert a.log.name == "loggingTools_test.A"
     assert b.log.name == "loggingTools_test.B"
+
+
+@pytest.mark.skipif(sys.version_info[:2] > (2, 7), reason="only for python2.7")
+@pytest.mark.parametrize(
+    "reset", [True, False], ids=["reset", "no-reset"]
+)
+def test_LastResortLogger(reset, capsys, caplog):
+    current = logging.getLoggerClass()
+    msg = "The quick brown fox jumps over the lazy dog"
+    try:
+        if reset:
+            _resetExistingLoggers()
+        else:
+            caplog.set_level(logging.ERROR, logger="myCustomLogger")
+        logging.lastResort = StderrHandler(logging.WARNING)
+        logging.setLoggerClass(LastResortLogger)
+        logger = logging.getLogger("myCustomLogger")
+        logger.error(msg)
+    finally:
+        del logging.lastResort
+        logging.setLoggerClass(current)
+
+    captured = capsys.readouterr()
+    if reset:
+        assert msg in captured.err
+        msg not in caplog.text
+    else:
+        msg in caplog.text
+        msg not in captured.err