From 1cd0247a4d1b8282631707ba06b514aeddc75782 Mon Sep 17 00:00:00 2001 From: Brett Cannon Date: Tue, 9 Sep 2008 01:52:27 +0000 Subject: [PATCH] Merged revisions 66321 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r66321 | brett.cannon | 2008-09-08 17:49:16 -0700 (Mon, 08 Sep 2008) | 7 lines warnings.catch_warnings() now returns a list or None instead of the custom WarningsRecorder object. This makes the API simpler to use as no special object must be learned. Closes issue 3781. Review by Benjamin Peterson. ........ --- Doc/library/warnings.rst | 110 ++++++++++++++++--------- Lib/test/test___all__.py | 4 +- Lib/test/test_hmac.py | 2 +- Lib/test/test_import.py | 4 +- Lib/test/test_re.py | 2 +- Lib/test/test_struct.py | 4 +- Lib/test/test_structmembers.py | 14 ++-- Lib/test/test_sundry.py | 2 +- Lib/test/test_warnings.py | 142 +++++++++++++++++++-------------- Lib/warnings.py | 46 +++++------ 10 files changed, 193 insertions(+), 137 deletions(-) diff --git a/Doc/library/warnings.rst b/Doc/library/warnings.rst index e3d3b5b208b..f9d01b25b1f 100644 --- a/Doc/library/warnings.rst +++ b/Doc/library/warnings.rst @@ -160,6 +160,67 @@ ImportWarning can also be enabled explicitly in Python code using:: warnings.simplefilter('default', ImportWarning) +.. _warning-suppress: + +Temporarily Suppressing Warnings +-------------------------------- + +If you are using code that you know will raise a warning, such some deprecated +function, but do not want to see the warning, then suppress the warning using +the :class:`catch_warnings` context manager:: + + import warnings + + def fxn(): + warnings.warn("deprecated", DeprecationWarning) + + with warnings.catch_warnings(): + warnings.simplefilter("ignore") + fxn() + +While within the context manager all warnings will simply be ignored. This +allows you to use known-deprecated code without having to see the warning while +not suppressing the warning for other code that might not be aware of its use +of deprecated code. + + +.. _warning-testing: + +Testing Warnings +---------------- + +To test warnings raised by code, use the :class:`catch_warnings` context +manager. With it you can temporarily mutate the warnings filter to facilitate +your testing. For instance, do the following to capture all raised warnings to +check:: + + import warnings + + def fxn(): + warnings.warn("deprecated", DeprecationWarning) + + with warnings.catch_warnings(record=True) as w: + # Cause all warnings to always be triggered. + warnings.simplefilter("always") + # Trigger a warning. + fxn() + # Verify some things + assert len(w) == 1 + assert isinstance(w[-1].category, DeprecationWarning) + assert "deprecated" in str(w[-1].message) + +One can also cause all warnings to be exceptions by using ``error`` instead of +``always``. One thing to be aware of is that if a warning has already been +raised because of a ``once``/``default`` rule, then no matter what filters are +set the warning will not be seen again unless the warnings registry related to +the warning has been cleared. + +Once the context manager exits, the warnings filter is restored to its state +when the context was entered. This prevents tests from changing the warnings +filter in unexpected ways between tests and leading to indeterminate test +results. + + .. _warning-functions: Available Functions @@ -248,31 +309,22 @@ Available Functions and calls to :func:`simplefilter`. -Available Classes ------------------ +Available Context Managers +-------------------------- .. class:: catch_warnings([\*, record=False, module=None]) - A context manager that guards the warnings filter from being permanently - mutated. The manager returns an instance of :class:`WarningsRecorder`. The - *record* argument specifies whether warnings that would typically be - handled by :func:`showwarning` should instead be recorded by the - :class:`WarningsRecorder` instance. This argument is typically set when - testing for expected warnings behavior. The *module* argument may be a - module object that is to be used instead of the :mod:`warnings` module. - This argument should only be set when testing the :mod:`warnings` module - or some similar use-case. + A context manager that copies and, upon exit, restores the warnings filter. + If the *record* argument is False (the default) the context manager returns + :class:`None`. If *record* is true, a list is returned that is populated + with objects as seen by a custom :func:`showwarning` function (which also + suppresses output to ``sys.stdout``). Each object has attributes with the + same names as the arguments to :func:`showwarning`. - Typical usage of the context manager is like so:: - - def fxn(): - warn("fxn is deprecated", DeprecationWarning) - return "spam spam bacon spam" - - # The function 'fxn' is known to raise a DeprecationWarning. - with catch_warnings() as w: - warnings.filterwarning('ignore', 'fxn is deprecated', DeprecationWarning) - fxn() # DeprecationWarning is temporarily suppressed. + The *module* argument takes a module that will be used instead of the + module returned when you import :mod:`warnings` whose filter will be + protected. This arguments exists primarily for testing the :mod:`warnings` + module itself. .. versionadded:: 2.6 @@ -280,19 +332,3 @@ Available Classes Constructor arguments turned into keyword-only arguments. - -.. class:: WarningsRecorder() - - A subclass of :class:`list` that stores all warnings passed to - :func:`showwarning` when returned by a :class:`catch_warnings` context - manager created with its *record* argument set to ``True``. Each recorded - warning is represented by an object whose attributes correspond to the - arguments to :func:`showwarning`. As a convenience, a - :class:`WarningsRecorder` instance has the attributes of the last - recorded warning set on the :class:`WarningsRecorder` instance as well. - - .. method:: reset() - - Delete all recorded warnings. - - .. versionadded:: 2.6 diff --git a/Lib/test/test___all__.py b/Lib/test/test___all__.py index ba8f75b8a76..052cc20c45d 100644 --- a/Lib/test/test___all__.py +++ b/Lib/test/test___all__.py @@ -1,5 +1,5 @@ import unittest -from test.support import run_unittest, catch_warning +from test.support import run_unittest import sys import warnings @@ -8,7 +8,7 @@ class AllTest(unittest.TestCase): def check_all(self, modname): names = {} - with catch_warning(): + with warnings.catch_warnings(): warnings.filterwarnings("ignore", ".* (module|package)", DeprecationWarning) try: diff --git a/Lib/test/test_hmac.py b/Lib/test/test_hmac.py index 43953cfeb04..f7ac8efbb0c 100644 --- a/Lib/test/test_hmac.py +++ b/Lib/test/test_hmac.py @@ -211,7 +211,7 @@ def update(self, v): def digest(self): return self._x.digest() - with support.catch_warning(): + with warnings.catch_warnings(): warnings.simplefilter('error', RuntimeWarning) try: hmac.HMAC(b'a', b'b', digestmod=MockCrazyHash) diff --git a/Lib/test/test_import.py b/Lib/test/test_import.py index aa65c7a419b..0dbbbf04c50 100644 --- a/Lib/test/test_import.py +++ b/Lib/test/test_import.py @@ -6,7 +6,7 @@ import py_compile import warnings import imp -from test.support import unlink, TESTFN, unload, run_unittest, catch_warning +from test.support import unlink, TESTFN, unload, run_unittest def remove_files(name): @@ -153,7 +153,7 @@ def test_import_name_binding(self): self.assert_(y is test.support, y.__name__) def test_import_initless_directory_warning(self): - with catch_warning(): + with warnings.catch_warnings(): # Just a random non-package directory we always expect to be # somewhere in sys.path... warnings.simplefilter('error', ImportWarning) diff --git a/Lib/test/test_re.py b/Lib/test/test_re.py index 17370bb4564..6ee84c62af8 100644 --- a/Lib/test/test_re.py +++ b/Lib/test/test_re.py @@ -1,7 +1,7 @@ import sys sys.path = ['.'] + sys.path -from test.support import verbose, run_unittest, catch_warning +from test.support import verbose, run_unittest import re from re import Scanner import sys, os, traceback diff --git a/Lib/test/test_struct.py b/Lib/test/test_struct.py index 6dc0e8dc05d..00219b8ca0e 100644 --- a/Lib/test/test_struct.py +++ b/Lib/test/test_struct.py @@ -4,7 +4,7 @@ import warnings from functools import wraps -from test.support import TestFailed, verbose, run_unittest, catch_warning +from test.support import TestFailed, verbose, run_unittest import sys ISBIGENDIAN = sys.byteorder == "big" @@ -34,7 +34,7 @@ def bigendian_to_native(value): def with_warning_restore(func): @wraps(func) def decorator(*args, **kw): - with catch_warning(): + with warnings.catch_warnings(): # We need this function to warn every time, so stick an # unqualifed 'always' at the head of the filter list warnings.simplefilter("always") diff --git a/Lib/test/test_structmembers.py b/Lib/test/test_structmembers.py index d6c9fea2175..878223a38fa 100644 --- a/Lib/test/test_structmembers.py +++ b/Lib/test/test_structmembers.py @@ -66,35 +66,35 @@ def test_types(self): class TestWarnings(unittest.TestCase): def has_warned(self, w): - self.assertEqual(w.category, RuntimeWarning) + self.assertEqual(w[-1].category, RuntimeWarning) def test_byte_max(self): - with support.catch_warning() as w: + with warnings.catch_warnings(record=True) as w: ts.T_BYTE = CHAR_MAX+1 self.has_warned(w) def test_byte_min(self): - with support.catch_warning() as w: + with warnings.catch_warnings(record=True) as w: ts.T_BYTE = CHAR_MIN-1 self.has_warned(w) def test_ubyte_max(self): - with support.catch_warning() as w: + with warnings.catch_warnings(record=True) as w: ts.T_UBYTE = UCHAR_MAX+1 self.has_warned(w) def test_short_max(self): - with support.catch_warning() as w: + with warnings.catch_warnings(record=True) as w: ts.T_SHORT = SHRT_MAX+1 self.has_warned(w) def test_short_min(self): - with support.catch_warning() as w: + with warnings.catch_warnings(record=True) as w: ts.T_SHORT = SHRT_MIN-1 self.has_warned(w) def test_ushort_max(self): - with support.catch_warning() as w: + with warnings.catch_warnings(record=True) as w: ts.T_USHORT = USHRT_MAX+1 self.has_warned(w) diff --git a/Lib/test/test_sundry.py b/Lib/test/test_sundry.py index a99d2c0dcd7..6b425c6fa54 100644 --- a/Lib/test/test_sundry.py +++ b/Lib/test/test_sundry.py @@ -7,7 +7,7 @@ class TestUntestedModules(unittest.TestCase): def test_at_least_import_untested_modules(self): - with support.catch_warning(): + with warnings.catch_warnings(record=True): import aifc import bdb import cgitb diff --git a/Lib/test/test_warnings.py b/Lib/test/test_warnings.py index 087bf3d871a..199e6fca3d9 100644 --- a/Lib/test/test_warnings.py +++ b/Lib/test/test_warnings.py @@ -72,64 +72,69 @@ class FilterTests(object): """Testing the filtering functionality.""" def test_error(self): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(module=self.module) as w: self.module.resetwarnings() self.module.filterwarnings("error", category=UserWarning) self.assertRaises(UserWarning, self.module.warn, "FilterTests.test_error") def test_ignore(self): - with support.catch_warning(module=self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: self.module.resetwarnings() self.module.filterwarnings("ignore", category=UserWarning) self.module.warn("FilterTests.test_ignore", UserWarning) self.assertEquals(len(w), 0) def test_always(self): - with support.catch_warning(module=self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: self.module.resetwarnings() self.module.filterwarnings("always", category=UserWarning) message = "FilterTests.test_always" self.module.warn(message, UserWarning) - self.assert_(message, w.message) + self.assert_(message, w[-1].message) self.module.warn(message, UserWarning) - self.assert_(w.message, message) + self.assert_(w[-1].message, message) def test_default(self): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: self.module.resetwarnings() self.module.filterwarnings("default", category=UserWarning) message = UserWarning("FilterTests.test_default") for x in range(2): self.module.warn(message, UserWarning) if x == 0: - self.assertEquals(w.message, message) - w.reset() + self.assertEquals(w[-1].message, message) + del w[:] elif x == 1: - self.assert_(not len(w), "unexpected warning: " + str(w)) + self.assertEquals(len(w), 0) else: raise ValueError("loop variant unhandled") def test_module(self): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: self.module.resetwarnings() self.module.filterwarnings("module", category=UserWarning) message = UserWarning("FilterTests.test_module") self.module.warn(message, UserWarning) - self.assertEquals(w.message, message) - w.reset() + self.assertEquals(w[-1].message, message) + del w[:] self.module.warn(message, UserWarning) - self.assert_(not len(w), "unexpected message: " + str(w)) + self.assertEquals(len(w), 0) def test_once(self): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: self.module.resetwarnings() self.module.filterwarnings("once", category=UserWarning) message = UserWarning("FilterTests.test_once") self.module.warn_explicit(message, UserWarning, "test_warnings.py", 42) - self.assertEquals(w.message, message) - w.reset() + self.assertEquals(w[-1].message, message) + del w[:] self.module.warn_explicit(message, UserWarning, "test_warnings.py", 13) self.assertEquals(len(w), 0) @@ -138,19 +143,20 @@ def test_once(self): self.assertEquals(len(w), 0) def test_inheritance(self): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(module=self.module) as w: self.module.resetwarnings() self.module.filterwarnings("error", category=Warning) self.assertRaises(UserWarning, self.module.warn, "FilterTests.test_inheritance", UserWarning) def test_ordering(self): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: self.module.resetwarnings() self.module.filterwarnings("ignore", category=UserWarning) self.module.filterwarnings("error", category=UserWarning, append=True) - w.reset() + del w[:] try: self.module.warn("FilterTests.test_ordering", UserWarning) except UserWarning: @@ -160,28 +166,29 @@ def test_ordering(self): def test_filterwarnings(self): # Test filterwarnings(). # Implicitly also tests resetwarnings(). - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: self.module.filterwarnings("error", "", Warning, "", 0) self.assertRaises(UserWarning, self.module.warn, 'convert to error') self.module.resetwarnings() text = 'handle normally' self.module.warn(text) - self.assertEqual(str(w.message), text) - self.assert_(w.category is UserWarning) + self.assertEqual(str(w[-1].message), text) + self.assert_(w[-1].category is UserWarning) self.module.filterwarnings("ignore", "", Warning, "", 0) text = 'filtered out' self.module.warn(text) - self.assertNotEqual(str(w.message), text) + self.assertNotEqual(str(w[-1].message), text) self.module.resetwarnings() self.module.filterwarnings("error", "hex*", Warning, "", 0) self.assertRaises(UserWarning, self.module.warn, 'hex/oct') text = 'nonmatching text' self.module.warn(text) - self.assertEqual(str(w.message), text) - self.assert_(w.category is UserWarning) + self.assertEqual(str(w[-1].message), text) + self.assert_(w[-1].category is UserWarning) class CFilterTests(BaseTest, FilterTests): module = c_warnings @@ -195,12 +202,13 @@ class WarnTests(unittest.TestCase): """Test warnings.warn() and warnings.warn_explicit().""" def test_message(self): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: for i in range(4): text = 'multi %d' %i # Different text on each call. self.module.warn(text) - self.assertEqual(str(w.message), text) - self.assert_(w.category is UserWarning) + self.assertEqual(str(w[-1].message), text) + self.assert_(w[-1].category is UserWarning) # Issue 3639 def test_warn_nonstandard_types(self): @@ -210,35 +218,45 @@ def test_warn_nonstandard_types(self): self.module.warn(ob) # Don't directly compare objects since # ``Warning() != Warning()``. - self.assertEquals(str(w.message), str(UserWarning(ob))) + self.assertEquals(str(w[-1].message), str(UserWarning(ob))) def test_filename(self): with warnings_state(self.module): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: warning_tests.inner("spam1") - self.assertEqual(os.path.basename(w.filename), "warning_tests.py") + self.assertEqual(os.path.basename(w[-1].filename), + "warning_tests.py") warning_tests.outer("spam2") - self.assertEqual(os.path.basename(w.filename), "warning_tests.py") + self.assertEqual(os.path.basename(w[-1].filename), + "warning_tests.py") def test_stacklevel(self): # Test stacklevel argument # make sure all messages are different, so the warning won't be skipped with warnings_state(self.module): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: warning_tests.inner("spam3", stacklevel=1) - self.assertEqual(os.path.basename(w.filename), "warning_tests.py") + self.assertEqual(os.path.basename(w[-1].filename), + "warning_tests.py") warning_tests.outer("spam4", stacklevel=1) - self.assertEqual(os.path.basename(w.filename), "warning_tests.py") + self.assertEqual(os.path.basename(w[-1].filename), + "warning_tests.py") warning_tests.inner("spam5", stacklevel=2) - self.assertEqual(os.path.basename(w.filename), "test_warnings.py") + self.assertEqual(os.path.basename(w[-1].filename), + "test_warnings.py") warning_tests.outer("spam6", stacklevel=2) - self.assertEqual(os.path.basename(w.filename), "warning_tests.py") + self.assertEqual(os.path.basename(w[-1].filename), + "warning_tests.py") warning_tests.outer("spam6.5", stacklevel=3) - self.assertEqual(os.path.basename(w.filename), "test_warnings.py") + self.assertEqual(os.path.basename(w[-1].filename), + "test_warnings.py") warning_tests.inner("spam7", stacklevel=9999) - self.assertEqual(os.path.basename(w.filename), "sys") + self.assertEqual(os.path.basename(w[-1].filename), + "sys") def test_missing_filename_not_main(self): # If __file__ is not specified and __main__ is not the module name, @@ -247,9 +265,10 @@ def test_missing_filename_not_main(self): try: del warning_tests.__file__ with warnings_state(self.module): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: warning_tests.inner("spam8", stacklevel=1) - self.assertEqual(w.filename, warning_tests.__name__) + self.assertEqual(w[-1].filename, warning_tests.__name__) finally: warning_tests.__file__ = filename @@ -264,9 +283,10 @@ def test_missing_filename_main_with_argv(self): del warning_tests.__file__ warning_tests.__name__ = '__main__' with warnings_state(self.module): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: warning_tests.inner('spam9', stacklevel=1) - self.assertEqual(w.filename, sys.argv[0]) + self.assertEqual(w[-1].filename, sys.argv[0]) finally: warning_tests.__file__ = filename warning_tests.__name__ = module_name @@ -282,9 +302,10 @@ def test_missing_filename_main_without_argv(self): warning_tests.__name__ = '__main__' del sys.argv with warnings_state(self.module): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: warning_tests.inner('spam10', stacklevel=1) - self.assertEqual(w.filename, '__main__') + self.assertEqual(w[-1].filename, '__main__') finally: warning_tests.__file__ = filename warning_tests.__name__ = module_name @@ -302,9 +323,10 @@ def test_missing_filename_main_with_argv_empty_string(self): warning_tests.__name__ = '__main__' sys.argv = [''] with warnings_state(self.module): - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: warning_tests.inner('spam11', stacklevel=1) - self.assertEqual(w.filename, '__main__') + self.assertEqual(w[-1].filename, '__main__') finally: warning_tests.__file__ = file_name warning_tests.__name__ = module_name @@ -337,7 +359,7 @@ class WCmdLineTests(unittest.TestCase): def test_improper_input(self): # Uses the private _setoption() function to test the parsing # of command-line warning arguments - with support.catch_warning(self.module): + with original_warnings.catch_warnings(module=self.module): self.assertRaises(self.module._OptionError, self.module._setoption, '1:2:3:4:5:6') self.assertRaises(self.module._OptionError, @@ -362,7 +384,7 @@ class _WarningsTests(BaseTest): def test_filter(self): # Everything should function even if 'filters' is not in warnings. - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(module=self.module) as w: self.module.filterwarnings("error", "", Warning, "", 0) self.assertRaises(UserWarning, self.module.warn, 'convert to error') @@ -377,21 +399,22 @@ def test_onceregistry(self): try: original_registry = self.module.onceregistry __warningregistry__ = {} - with support.catch_warning(self.module) as w: + with original_warnings.catch_warnings(record=True, + module=self.module) as w: self.module.resetwarnings() self.module.filterwarnings("once", category=UserWarning) self.module.warn_explicit(message, UserWarning, "file", 42) - self.failUnlessEqual(w.message, message) - w.reset() + self.failUnlessEqual(w[-1].message, message) + del w[:] self.module.warn_explicit(message, UserWarning, "file", 42) self.assertEquals(len(w), 0) # Test the resetting of onceregistry. self.module.onceregistry = {} __warningregistry__ = {} self.module.warn('onceregistry test') - self.failUnlessEqual(w.message.args, message.args) + self.failUnlessEqual(w[-1].message.args, message.args) # Removal of onceregistry is okay. - w.reset() + del w[:] del self.module.onceregistry __warningregistry__ = {} self.module.warn_explicit(message, UserWarning, "file", 42) @@ -402,7 +425,7 @@ def test_onceregistry(self): def test_showwarning_missing(self): # Test that showwarning() missing is okay. text = 'del showwarning test' - with support.catch_warning(self.module): + with original_warnings.catch_warnings(module=self.module): self.module.filterwarnings("always", category=UserWarning) del self.module.showwarning with support.captured_output('stderr') as stream: @@ -423,7 +446,7 @@ def test_showwarning_not_callable(self): def test_show_warning_output(self): # With showarning() missing, make sure that output is okay. text = 'test show_warning' - with support.catch_warning(self.module): + with original_warnings.catch_warnings(module=self.module): self.module.filterwarnings("always", category=UserWarning) del self.module.showwarning with support.captured_output('stderr') as stream: @@ -494,6 +517,7 @@ class CWarningsDisplayTests(BaseTest, WarningsDisplayTests): class PyWarningsDisplayTests(BaseTest, WarningsDisplayTests): module = py_warnings + class CatchWarningTests(BaseTest): """Test catch_warnings().""" @@ -517,12 +541,12 @@ def test_catch_warnings_recording(self): self.assertEqual(w, []) wmod.simplefilter("always") wmod.warn("foo") - self.assertEqual(str(w.message), "foo") + self.assertEqual(str(w[-1].message), "foo") wmod.warn("bar") - self.assertEqual(str(w.message), "bar") + self.assertEqual(str(w[-1].message), "bar") self.assertEqual(str(w[0].message), "foo") self.assertEqual(str(w[1].message), "bar") - w.reset() + del w[:] self.assertEqual(w, []) orig_showwarning = wmod.showwarning with support.catch_warning(module=wmod, record=False) as w: diff --git a/Lib/warnings.py b/Lib/warnings.py index 566e0b98c09..0e147db8715 100644 --- a/Lib/warnings.py +++ b/Lib/warnings.py @@ -7,7 +7,7 @@ import sys __all__ = ["warn", "showwarning", "formatwarning", "filterwarnings", - "resetwarnings"] + "resetwarnings", "catch_warnings"] def showwarning(message, category, filename, lineno, file=None, line=None): @@ -274,28 +274,20 @@ def __str__(self): self.filename, self.lineno, self.line)) -class WarningsRecorder(list): - - """Record the result of various showwarning() calls.""" - - def showwarning(self, *args, **kwargs): - self.append(WarningMessage(*args, **kwargs)) - - def __getattr__(self, attr): - return getattr(self[-1], attr) - - def reset(self): - del self[:] - - class catch_warnings(object): - """Guard the warnings filter from being permanently changed and optionally - record the details of any warnings that are issued. + """A context manager that copies and restores the warnings filter upon + exiting the context. - Context manager returns an instance of warnings.WarningRecorder which is a - list of WarningMessage instances. Attributes on WarningRecorder are - redirected to the last created WarningMessage instance. + The 'record' argument specifies whether warnings should be captured by a + custom implementation of warnings.showwarning() and be appended to a list + returned by the context manager. Otherwise None is returned by the context + manager. The objects appended to the list are arguments whose attributes + mirror the arguments to showwarning(). + + The 'module' argument is to specify an alternative module to the module + named 'warnings' and imported under that name. This argument is only useful + when testing the warnings module itself. """ @@ -307,17 +299,21 @@ def __init__(self, *, record=False, module=None): keyword-only. """ - self._recorder = WarningsRecorder() if record else None + self._record = record self._module = sys.modules['warnings'] if module is None else module def __enter__(self): self._filters = self._module.filters self._module.filters = self._filters[:] self._showwarning = self._module.showwarning - if self._recorder is not None: - self._recorder.reset() # In case the instance is being reused. - self._module.showwarning = self._recorder.showwarning - return self._recorder + if self._record: + log = [] + def showwarning(*args, **kwargs): + log.append(WarningMessage(*args, **kwargs)) + self._module.showwarning = showwarning + return log + else: + return None def __exit__(self, *exc_info): self._module.filters = self._filters