bpo-40275: Avoid importing logging in test.support

Doc/library/test.rst

@@ -1410,11 +1410,6 @@ The :mod:`test.support` module defines the following classes:
  Run *test* and return the result.
 
 
-.. class:: TestHandler(logging.handlers.BufferingHandler)
-
- Class for logging support.
-
-
 .. class:: FakePath(path)
 
  Simple :term:`path-like object`. It implements the :meth:`__fspath__`

Lib/test/support/__init__.py

@@ -15,7 +15,6 @@
 import importlib
 import importlib.util
 import locale
-import logging.handlers
 import os
 import platform
 import re
@@ -99,8 +98,6 @@
  "open_urlresource",
  # processes
  'temp_umask', "reap_children",
- # logging
- "TestHandler",
  # threads
  "threading_setup", "threading_cleanup", "reap_threads", "start_threads",
  # miscellaneous
@@ -2368,37 +2365,6 @@ def optim_args_from_interpreter_flags():
  optimization settings in sys.flags."""
  return subprocess._optim_args_from_interpreter_flags()
 
-#============================================================
-# Support for assertions about logging.
-#============================================================
-
-class TestHandler(logging.handlers.BufferingHandler):
- def __init__(self, matcher):
- # BufferingHandler takes a "capacity" argument
- # so as to know when to flush. As we're overriding
- # shouldFlush anyway, we can set a capacity of zero.
- # You can call flush() manually to clear out the
- # buffer.
- logging.handlers.BufferingHandler.__init__(self, 0)
- self.matcher = matcher
-
- def shouldFlush(self):
- return False
-
- def emit(self, record):
- self.format(record)
- self.buffer.append(record.__dict__)
-
- def matches(self, **kwargs):
- """
- Look for a saved dict whose keys/values match the supplied arguments.
- """
- result = False
- for d in self.buffer:
- if self.matcher.matches(d, **kwargs):
- result = True
- break
- return result
 
 class Matcher(object):
 

Lib/test/support/logging_helper.py

@@ -0,0 +1,29 @@
+import logging.handlers
+
+class TestHandler(logging.handlers.BufferingHandler):
+ def __init__(self, matcher):
+ # BufferingHandler takes a "capacity" argument
+ # so as to know when to flush. As we're overriding
+ # shouldFlush anyway, we can set a capacity of zero.
+ # You can call flush() manually to clear out the
+ # buffer.
+ logging.handlers.BufferingHandler.__init__(self, 0)
+ self.matcher = matcher
+
+ def shouldFlush(self):
+ return False
+
+ def emit(self, record):
+ self.format(record)
+ self.buffer.append(record.__dict__)
+
+ def matches(self, **kwargs):
+ """
+ Look for a saved dict whose keys/values match the supplied arguments.
+ """
+ result = False
+ for d in self.buffer:
+ if self.matcher.matches(d, **kwargs):
+ result = True
+ break
+ return result

Lib/test/test_logging.py

@@ -44,6 +44,7 @@
 from test.support.script_helper import assert_python_ok, assert_python_failure
 from test import support
 from test.support import socket_helper
+from test.support.logging_helper import TestHandler
 import textwrap
 import threading
 import time
@@ -3524,7 +3525,7 @@ def test_formatting(self):
  @unittest.skipUnless(hasattr(logging.handlers, 'QueueListener'),
  'logging.handlers.QueueListener required for this test')
  def test_queue_listener(self):
- handler = support.TestHandler(support.Matcher())
+ handler = TestHandler(support.Matcher())
  listener = logging.handlers.QueueListener(self.queue, handler)
  listener.start()
  try:
@@ -3540,7 +3541,7 @@ def test_queue_listener(self):
 
  # Now test with respect_handler_level set
 
- handler = support.TestHandler(support.Matcher())
+ handler = TestHandler(support.Matcher())
  handler.setLevel(logging.CRITICAL)
  listener = logging.handlers.QueueListener(self.queue, handler,
  respect_handler_level=True)

Lib/unittest/_log.py

@@ -0,0 +1,69 @@
+import logging
+import collections
+
+from .case import _BaseTestCaseContext
+
+
+_LoggingWatcher = collections.namedtuple("_LoggingWatcher",
+ ["records", "output"])
+
+class _CapturingHandler(logging.Handler):
+ """
+ A logging handler capturing all (raw and formatted) logging output.
+ """
+
+ def __init__(self):
+ logging.Handler.__init__(self)
+ self.watcher = _LoggingWatcher([], [])
+
+ def flush(self):
+ pass
+
+ def emit(self, record):
+ self.watcher.records.append(record)
+ msg = self.format(record)
+ self.watcher.output.append(msg)
+
+
+class _AssertLogsContext(_BaseTestCaseContext):
+ """A context manager used to implement TestCase.assertLogs()."""
+
+ LOGGING_FORMAT = "%(levelname)s:%(name)s:%(message)s"
+
+ def __init__(self, test_case, logger_name, level):
+ _BaseTestCaseContext.__init__(self, test_case)
+ self.logger_name = logger_name
+ if level:
+ self.level = logging._nameToLevel.get(level, level)
+ else:
+ self.level = logging.INFO
+ self.msg = None
+
+ def __enter__(self):
+ if isinstance(self.logger_name, logging.Logger):
+ logger = self.logger = self.logger_name
+ else:
+ logger = self.logger = logging.getLogger(self.logger_name)
+ formatter = logging.Formatter(self.LOGGING_FORMAT)
+ handler = _CapturingHandler()
+ handler.setFormatter(formatter)
+ self.watcher = handler.watcher
+ self.old_handlers = logger.handlers[:]
+ self.old_level = logger.level
+ self.old_propagate = logger.propagate
+ logger.handlers = [handler]
+ logger.setLevel(self.level)
+ logger.propagate = False
+ return handler.watcher
+
+ def __exit__(self, exc_type, exc_value, tb):
+ self.logger.handlers = self.old_handlers
+ self.logger.propagate = self.old_propagate
+ self.logger.setLevel(self.old_level)
+ if exc_type is not None:
+ # let unexpected exceptions pass through
+ return False
+ if len(self.watcher.records) == 0:
+ self._raiseFailure(
+ "no logs of level{} or higher triggered on{}"
+ .format(logging.getLevelName(self.level), self.logger.name))

Lib/unittest/case.py

@@ -3,7 +3,6 @@
 import sys
 import functools
 import difflib
-import logging
 import pprint
 import re
 import warnings
@@ -297,73 +296,6 @@ def __exit__(self, exc_type, exc_value, tb):
 
 
 
-_LoggingWatcher = collections.namedtuple("_LoggingWatcher",
- ["records", "output"])
-
-
-class _CapturingHandler(logging.Handler):
- """
- A logging handler capturing all (raw and formatted) logging output.
- """
-
- def __init__(self):
- logging.Handler.__init__(self)
- self.watcher = _LoggingWatcher([], [])
-
- def flush(self):
- pass
-
- def emit(self, record):
- self.watcher.records.append(record)
- msg = self.format(record)
- self.watcher.output.append(msg)
-
-
-
-class _AssertLogsContext(_BaseTestCaseContext):
- """A context manager used to implement TestCase.assertLogs()."""
-
- LOGGING_FORMAT = "%(levelname)s:%(name)s:%(message)s"
-
- def __init__(self, test_case, logger_name, level):
- _BaseTestCaseContext.__init__(self, test_case)
- self.logger_name = logger_name
- if level:
- self.level = logging._nameToLevel.get(level, level)
- else:
- self.level = logging.INFO
- self.msg = None
-
- def __enter__(self):
- if isinstance(self.logger_name, logging.Logger):
- logger = self.logger = self.logger_name
- else:
- logger = self.logger = logging.getLogger(self.logger_name)
- formatter = logging.Formatter(self.LOGGING_FORMAT)
- handler = _CapturingHandler()
- handler.setFormatter(formatter)
- self.watcher = handler.watcher
- self.old_handlers = logger.handlers[:]
- self.old_level = logger.level
- self.old_propagate = logger.propagate
- logger.handlers = [handler]
- logger.setLevel(self.level)
- logger.propagate = False
- return handler.watcher
-
- def __exit__(self, exc_type, exc_value, tb):
- self.logger.handlers = self.old_handlers
- self.logger.propagate = self.old_propagate
- self.logger.setLevel(self.old_level)
- if exc_type is not None:
- # let unexpected exceptions pass through
- return False
- if len(self.watcher.records) == 0:
- self._raiseFailure(
- "no logs of level{} or higher triggered on{}"
- .format(logging.getLevelName(self.level), self.logger.name))
-
-
 class _OrderedChainMap(collections.ChainMap):
  def __iter__(self):
  seen = set()
@@ -854,6 +786,8 @@ def assertLogs(self, logger=None, level=None):
  self.assertEqual(cm.output, ['INFO:foo:first message',
  'ERROR:foo.bar:second message'])
  """
+ # Lazy import to avoid importing logging if it is not needed.
+ from ._log import _AssertLogsContext
  return _AssertLogsContext(self, logger, level)
 
  def _getAssertEqualityFunc(self, first, second):

Misc/NEWS.d/next/Library/2020-04-20-19-06-55.bpo-40275.9UcN2g.rst

@@ -0,0 +1,2 @@
+The :mod:`logging` package is now imported lazily in :mod:`unittest` only
+when the :meth:`~unittest.TestCase.assertLogs` assertion is used.