Merge in r66135. Doing also required removing a stale DeprecationWarning along

with moving warnings.catch_warnings() over to keyword-only parameters for its
constructor (as documented in the 2.6 docs).

Doc/library/warnings.rst

@@ -247,3 +247,52 @@ Available Functions
    :func:`filterwarnings`, including that of the :option:`-W` command line options
    and calls to :func:`simplefilter`.
 
+
+Available Classes
+-----------------
+
+.. class:: catch_warnings([\*, record=False, module=None])
+
+    A context manager that guards the warnings filter from being permanentally
+    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.
+
+    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.
+
+    .. versionadded:: 2.6
+
+    .. versionchanged:: 3.0
+
+       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

Lib/test/support.py

@@ -19,7 +19,7 @@ __all__ = ["Error", "TestFailed", "TestSkipped", "ResourceDenied", "import_modul
            "is_resource_enabled", "requires", "find_unused_port", "bind_port",
            "fcmp", "is_jython", "TESTFN", "HOST", "FUZZ", "findfile", "verify",
            "vereq", "sortdict", "check_syntax_error", "open_urlresource",
-           "WarningMessage", "catch_warning", "CleanImport", "EnvironmentVarGuard",
+           "catch_warning", "CleanImport", "EnvironmentVarGuard",
            "TransientResource", "captured_output", "captured_stdout",
            "TransientResource", "transient_internet", "run_with_locale",
            "set_memlimit", "bigmemtest", "bigaddrspacetest", "BasicTestRunner",
@@ -368,47 +368,6 @@ def open_urlresource(url, *args, **kw):
     return open(fn, *args, **kw)
 
 
-class WarningMessage(object):
-    "Holds the result of a single showwarning() call"
-    _WARNING_DETAILS = "message category filename lineno line".split()
-    def __init__(self, message, category, filename, lineno, line=None):
-        for attr in self._WARNING_DETAILS:
-            setattr(self, attr, locals()[attr])
-        self._category_name = category.__name__ if category else None
-
-    def __str__(self):
-        return ("{message : %r, category : %r, filename : %r, lineno : %s, "
-                    "line : %r}" % (self.message, self._category_name,
-                                    self.filename, self.lineno, self.line))
-
-class WarningRecorder(object):
-    "Records the result of any showwarning calls"
-    def __init__(self):
-        self.warnings = []
-        self._set_last(None)
-
-    def _showwarning(self, message, category, filename, lineno,
-                    file=None, line=None):
-        wm = WarningMessage(message, category, filename, lineno, line)
-        self.warnings.append(wm)
-        self._set_last(wm)
-
-    def _set_last(self, last_warning):
-        if last_warning is None:
-            for attr in WarningMessage._WARNING_DETAILS:
-                setattr(self, attr, None)
-        else:
-            for attr in WarningMessage._WARNING_DETAILS:
-                setattr(self, attr, getattr(last_warning, attr))
-
-    def reset(self):
-        self.warnings = []
-        self._set_last(None)
-
-    def __str__(self):
-        return '[%s]' % (', '.join(map(str, self.warnings)))
-
-@contextlib.contextmanager
 def catch_warning(module=warnings, record=True):
     """Guard the warnings filter from being permanently changed and
     optionally record the details of any warnings that are issued.
@@ -419,20 +378,7 @@ def catch_warning(module=warnings, record=True):
             warnings.warn("foo")
             assert str(w.message) == "foo"
     """
-    original_filters = module.filters
-    original_showwarning = module.showwarning
-    if record:
-        recorder = WarningRecorder()
-        module.showwarning = recorder._showwarning
-    else:
-        recorder = None
-    try:
-        # Replace the filters with a copy of the original
-        module.filters = module.filters[:]
-        yield recorder
-    finally:
-        module.showwarning = original_showwarning
-        module.filters = original_filters
+    return warnings.catch_warnings(record=record, module=module)
 
 
 class CleanImport(object):

Lib/test/test_warnings.py

@@ -79,20 +79,19 @@ class FilterTests(object):
                                 "FilterTests.test_error")
 
     def test_ignore(self):
-        with support.catch_warning(self.module) as w:
+        with support.catch_warning(module=self.module) as w:
             self.module.resetwarnings()
             self.module.filterwarnings("ignore", category=UserWarning)
             self.module.warn("FilterTests.test_ignore", UserWarning)
-            self.assert_(not w.message)
+            self.assertEquals(len(w), 0)
 
     def test_always(self):
-        with support.catch_warning(self.module) as w:
+        with support.catch_warning(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)
-            w.message = None  # Reset.
             self.module.warn(message, UserWarning)
             self.assert_(w.message, message)
 
@@ -107,7 +106,7 @@ class FilterTests(object):
                     self.assertEquals(w.message, message)
                     w.reset()
                 elif x == 1:
-                    self.assert_(not w.message, "unexpected warning: " + str(w))
+                    self.assert_(not len(w), "unexpected warning: " + str(w))
                 else:
                     raise ValueError("loop variant unhandled")
 
@@ -120,7 +119,7 @@ class FilterTests(object):
             self.assertEquals(w.message, message)
             w.reset()
             self.module.warn(message, UserWarning)
-            self.assert_(not w.message, "unexpected message: " + str(w))
+            self.assert_(not len(w), "unexpected message: " + str(w))
 
     def test_once(self):
         with support.catch_warning(self.module) as w:
@@ -133,10 +132,10 @@ class FilterTests(object):
             w.reset()
             self.module.warn_explicit(message, UserWarning, "test_warnings.py",
                                     13)
-            self.assert_(not w.message)
+            self.assertEquals(len(w), 0)
             self.module.warn_explicit(message, UserWarning, "test_warnings2.py",
                                     42)
-            self.assert_(not w.message)
+            self.assertEquals(len(w), 0)
 
     def test_inheritance(self):
         with support.catch_warning(self.module) as w:
@@ -156,7 +155,7 @@ class FilterTests(object):
                 self.module.warn("FilterTests.test_ordering", UserWarning)
             except UserWarning:
                 self.fail("order handling for actions failed")
-            self.assert_(not w.message)
+            self.assertEquals(len(w), 0)
 
     def test_filterwarnings(self):
         # Test filterwarnings().
@@ -317,7 +316,6 @@ class WarnTests(unittest.TestCase):
                             None, Warning, None, 1, registry=42)
 
 
-
 class CWarnTests(BaseTest, WarnTests):
     module = c_warnings
 
@@ -377,7 +375,7 @@ class _WarningsTests(BaseTest):
                 self.failUnlessEqual(w.message, message)
                 w.reset()
                 self.module.warn_explicit(message, UserWarning, "file", 42)
-                self.assert_(not w.message)
+                self.assertEquals(len(w), 0)
                 # Test the resetting of onceregistry.
                 self.module.onceregistry = {}
                 __warningregistry__ = {}
@@ -388,7 +386,7 @@ class _WarningsTests(BaseTest):
                 del self.module.onceregistry
                 __warningregistry__ = {}
                 self.module.warn_explicit(message, UserWarning, "file", 42)
-                self.failUnless(not w.message)
+                self.assertEquals(len(w), 0)
         finally:
             self.module.onceregistry = original_registry
 
@@ -487,45 +485,45 @@ class CWarningsDisplayTests(BaseTest, WarningsDisplayTests):
 class PyWarningsDisplayTests(BaseTest, WarningsDisplayTests):
     module = py_warnings
 
-class WarningsSupportTests(object):
-    """Test the warning tools from test support module"""
+class CatchWarningTests(BaseTest):
 
-    def test_catch_warning_restore(self):
+    """Test catch_warnings()."""
+
+    def test_catch_warnings_restore(self):
         wmod = self.module
         orig_filters = wmod.filters
         orig_showwarning = wmod.showwarning
-        with support.catch_warning(wmod):
+        with support.catch_warning(module=wmod):
             wmod.filters = wmod.showwarning = object()
         self.assert_(wmod.filters is orig_filters)
         self.assert_(wmod.showwarning is orig_showwarning)
-        with support.catch_warning(wmod, record=False):
+        with support.catch_warning(module=wmod, record=False):
             wmod.filters = wmod.showwarning = object()
         self.assert_(wmod.filters is orig_filters)
         self.assert_(wmod.showwarning is orig_showwarning)
 
-    def test_catch_warning_recording(self):
+    def test_catch_warnings_recording(self):
         wmod = self.module
-        with support.catch_warning(wmod) as w:
-            self.assertEqual(w.warnings, [])
+        with support.catch_warning(module=wmod) as w:
+            self.assertEqual(w, [])
             wmod.simplefilter("always")
             wmod.warn("foo")
             self.assertEqual(str(w.message), "foo")
             wmod.warn("bar")
             self.assertEqual(str(w.message), "bar")
-            self.assertEqual(str(w.warnings[0].message), "foo")
-            self.assertEqual(str(w.warnings[1].message), "bar")
+            self.assertEqual(str(w[0].message), "foo")
+            self.assertEqual(str(w[1].message), "bar")
             w.reset()
-            self.assertEqual(w.warnings, [])
+            self.assertEqual(w, [])
         orig_showwarning = wmod.showwarning
-        with support.catch_warning(wmod, record=False) as w:
+        with support.catch_warning(module=wmod, record=False) as w:
             self.assert_(w is None)
             self.assert_(wmod.showwarning is orig_showwarning)
 
-
-class CWarningsSupportTests(BaseTest, WarningsSupportTests):
+class CCatchWarningTests(CatchWarningTests):
     module = c_warnings
 
-class PyWarningsSupportTests(BaseTest, WarningsSupportTests):
+class PyCatchWarningTests(CatchWarningTests):
     module = py_warnings
 
 
@@ -539,7 +537,7 @@ def test_main():
                                 CWCmdLineTests, PyWCmdLineTests,
                                 _WarningsTests,
                                 CWarningsDisplayTests, PyWarningsDisplayTests,
-                                CWarningsSupportTests, PyWarningsSupportTests,
+                                CCatchWarningTests, PyCatchWarningTests,
                              )
 
 

Lib/warnings.py

@@ -254,6 +254,76 @@ def warn_explicit(message, category, filename, lineno,
     showwarning(message, category, filename, lineno)
 
 
+class WarningMessage(object):
+
+    """Holds the result of a single showwarning() call."""
+
+    _WARNING_DETAILS = ("message", "category", "filename", "lineno", "file",
+                        "line")
+
+    def __init__(self, message, category, filename, lineno, file=None,
+                    line=None):
+        local_values = locals()
+        for attr in self._WARNING_DETAILS:
+            setattr(self, attr, local_values[attr])
+        self._category_name = category.__name__ if category else None
+
+    def __str__(self):
+        return ("{message : %r, category : %r, filename : %r, lineno : %s, "
+                    "line : %r}" % (self.message, self._category_name,
+                                    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.
+
+    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.
+
+    """
+
+    def __init__(self, *, record=False, module=None):
+        """Specify whether to record warnings and if an alternative module
+        should be used other than sys.modules['warnings'].
+
+        For compatibility with Python 3.0, please consider all arguments to be
+        keyword-only.
+
+        """
+        self._recorder = WarningsRecorder() if record else None
+        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
+
+    def __exit__(self, *exc_info):
+        self._module.filters = self._filters
+        self._module.showwarning = self._showwarning
+
+
 # filters contains a sequence of filter 5-tuples
 # The components of the 5-tuple are:
 # - an action: error, ignore, always, default, module, or once

Misc/NEWS

@@ -60,6 +60,9 @@ C API
 Library
 -------
 
+- Issue 3602: As part of the merge of r66135, make the parameters on
+  warnings.catch_warnings() keyword-only. Also remove a DeprecationWarning.
+
 - The deprecation warnings for the camelCase threading API names were removed.
 
 Extension Modules

Python/_warnings.c

@@ -386,49 +386,23 @@ warn_explicit(PyObject *category, PyObject *message,
             show_warning(filename, lineno, text, category, sourceline);
         }
         else {
-            const char *msg = "functions overriding warnings.showwarning() "
-                                "must support the 'line' argument";
-            const char *text_char = _PyUnicode_AsString(text);
-
-            if (strcmp(msg, text_char) == 0) {
-                /* Prevent infinite recursion by using built-in implementation
-                   of showwarning(). */
-                show_warning(filename, lineno, text, category, sourceline);
-            }
-            else {
-                PyObject *check_fxn;
-                PyObject *defaults;
-                PyObject *res;
-
-                if (PyMethod_Check(show_fxn))
-                    check_fxn = PyMethod_Function(show_fxn);
-                else if (PyFunction_Check(show_fxn))
-                    check_fxn = show_fxn;
-                else {
-                    PyErr_SetString(PyExc_TypeError,
-                                    "warnings.showwarning() must be set to a "
-                                    "function or method");
-                    Py_DECREF(show_fxn);
-                    goto cleanup;
-                }
+            PyObject *res;
 
-                defaults = PyFunction_GetDefaults(check_fxn);
-                /* A proper implementation of warnings.showwarning() should
-                    have at least two default arguments. */
-                if ((defaults == NULL) || (PyTuple_Size(defaults) < 2)) {
-                    if (PyErr_WarnEx(PyExc_DeprecationWarning, msg, 1) < 0) {
-                        Py_DECREF(show_fxn);
-                        goto cleanup;
-                    }
-                }
-                res = PyObject_CallFunctionObjArgs(show_fxn, message, category,
-                                                    filename, lineno_obj,
-                                                    NULL);
+            if (!PyMethod_Check(show_fxn) && !PyFunction_Check(show_fxn)) {
+                PyErr_SetString(PyExc_TypeError,
+                                "warnings.showwarning() must be set to a "
+                                "function or method");
                 Py_DECREF(show_fxn);
-                Py_XDECREF(res);
-                if (res == NULL)
-                    goto cleanup;
+                goto cleanup;
             }
+
+            res = PyObject_CallFunctionObjArgs(show_fxn, message, category,
+                                                filename, lineno_obj,
+                                                NULL);
+            Py_DECREF(show_fxn);
+            Py_XDECREF(res);
+            if (res == NULL)
+                goto cleanup;
         }
     }
     else /* if (rc == -1) */