[3.10] bpo-43988: Add test.support.check_disallow_instantiation() (GH-25757) (GH-26885)

(cherry picked from commit 4f725261c6, fbff5387c3, and 8cec740820)

Co-authored-by: Erlend Egeberg Aasland <erlend.aasland@innova.no>

Automerge-Triggered-By: GH:vstinner

Doc/library/test.rst

@@ -928,8 +928,16 @@ The :mod:`test.support` module defines the following functions:
    .. versionadded:: 3.10
 
 
+.. function:: check_disallow_instantiation(test_case, tp, *args, **kwds)
+
+   Assert that type *tp* cannot be instantiated using *args* and *kwds*.
+
+   .. versionadded:: 3.10
+
+
 The :mod:`test.support` module defines the following classes:
 
+
 .. class:: SuppressCrashReport()
 
    A context manager used to try to prevent crash dialog popups on tests that

Lib/sqlite3/test/dbapi.py

@@ -25,6 +25,7 @@ import unittest
 import sqlite3 as sqlite
 import sys
 
+from test.support import check_disallow_instantiation
 from test.support.os_helper import TESTFN, unlink
 
 
@@ -94,8 +95,7 @@ class ModuleTests(unittest.TestCase):
 
     def test_disallow_instantiation(self):
         cx = sqlite.connect(":memory:")
-        tp = type(cx("select 1"))
+        check_disallow_instantiation(self, type(cx("select 1")))
-        self.assertRaises(TypeError, tp)
 
 
 class ConnectionTests(unittest.TestCase):

Lib/test/support/__init__.py

@@ -40,6 +40,7 @@ __all__ = [
     "requires_IEEE_754", "requires_zlib",
     "anticipate_failure", "load_package_tests", "detect_api_mismatch",
     "check__all__", "skip_if_buggy_ucrt_strfptime",
+    "check_disallow_instantiation",
     # sys
     "is_jython", "is_android", "check_impl_detail", "unix_shell",
     "setswitchinterval",
@@ -1992,3 +1993,19 @@ def infinite_recursion(max_depth=75):
         yield
     finally:
         sys.setrecursionlimit(original_depth)
+
+
+def check_disallow_instantiation(testcase, tp, *args, **kwds):
+    """
+    Check that given type cannot be instantiated using *args and **kwds.
+
+    See bpo-43916: Add Py_TPFLAGS_DISALLOW_INSTANTIATION type flag.
+    """
+    mod = tp.__module__
+    name = tp.__name__
+    if mod != 'builtins':
+        qualname = f"{mod}.{name}"
+    else:
+        qualname = f"{name}"
+    msg = f"cannot create '{re.escape(qualname)}' instances"
+    testcase.assertRaisesRegex(TypeError, msg, tp, *args, **kwds)

Lib/test/test_array.py

@@ -42,9 +42,10 @@ class MiscTest(unittest.TestCase):
 
     @support.cpython_only
     def test_disallow_instantiation(self):
-        # Ensure that the type disallows instantiation (bpo-43916)
+        my_array = array.array("I")
-        tp = type(iter(array.array('I')))
+        support.check_disallow_instantiation(
-        self.assertRaises(TypeError, tp)
+            self, type(iter(my_array)), my_array
+        )
 
     @support.cpython_only
     def test_immutable(self):

Lib/test/test_curses.py

@@ -6,7 +6,8 @@ import sys
 import tempfile
 import unittest
 
-from test.support import requires, verbose, SaveSignals, cpython_only
+from test.support import (requires, verbose, SaveSignals, cpython_only,
+                          check_disallow_instantiation)
 from test.support.import_helper import import_module
 
 # Optionally test curses module.  This currently requires that the
@@ -1052,7 +1053,7 @@ class TestCurses(unittest.TestCase):
         # Ensure that the type disallows instantiation (bpo-43916)
         w = curses.newwin(10, 10)
         panel = curses.panel.new_panel(w)
-        self.assertRaises(TypeError, type(panel))
+        check_disallow_instantiation(self, type(panel))
 
     @requires_curses_func('is_term_resized')
     def test_is_term_resized(self):

Lib/test/test_dbm_gnu.py

@@ -31,8 +31,7 @@ class TestGdbm(unittest.TestCase):
     def test_disallow_instantiation(self):
         # Ensure that the type disallows instantiation (bpo-43916)
         self.g = gdbm.open(filename, 'c')
-        tp = type(self.g)
+        support.check_disallow_instantiation(self, type(self.g))
-        self.assertRaises(TypeError, tp)
 
     def test_key_methods(self):
         self.g = gdbm.open(filename, 'c')

Lib/test/test_embed.py

@@ -1541,9 +1541,7 @@ class StdPrinterTests(EmbeddingTestsMixin, unittest.TestCase):
     def test_disallow_instantiation(self):
         fd = self.get_stdout_fd()
         printer = self.create_printer(fd)
-        PyStdPrinter_Type = type(printer)
+        support.check_disallow_instantiation(self, type(printer))
-        with self.assertRaises(TypeError):
-            PyStdPrinter_Type(fd)
 
 
 if __name__ == "__main__":

Lib/test/test_functools.py

@@ -951,8 +951,9 @@ class TestCmpToKeyC(TestCmpToKey, unittest.TestCase):
     @support.cpython_only
     def test_disallow_instantiation(self):
         # Ensure that the type disallows instantiation (bpo-43916)
-        tp = type(c_functools.cmp_to_key(None))
+        support.check_disallow_instantiation(
-        self.assertRaises(TypeError, tp)
+            self, type(c_functools.cmp_to_key(None))
+        )
 
 
 class TestCmpToKeyPy(TestCmpToKey, unittest.TestCase):

Lib/test/test_hashlib.py

@@ -915,20 +915,13 @@ class HashLibTestCase(unittest.TestCase):
                 except ValueError:
                     continue
                 with self.subTest(constructor=constructor):
-                    hash_type = type(h)
+                    support.check_disallow_instantiation(self, type(h))
-                    self.assertRaises(TypeError, hash_type)
 
     @unittest.skipUnless(HASH is not None, 'need _hashlib')
-    def test_hash_disallow_instanciation(self):
+    def test_hash_disallow_instantiation(self):
         # internal types like _hashlib.HASH are not constructable
-        with self.assertRaisesRegex(
+        support.check_disallow_instantiation(self, HASH)
-            TypeError, "cannot create '_hashlib.HASH' instance"
+        support.check_disallow_instantiation(self, HASHXOF)
-        ):
-            HASH()
-        with self.assertRaisesRegex(
-            TypeError, "cannot create '_hashlib.HASHXOF' instance"
-        ):
-            HASHXOF()
 
     def test_readonly_types(self):
         for algorithm, constructors in self.constructors_to_test.items():

Lib/test/test_hmac.py

@@ -6,7 +6,7 @@ import unittest
 import unittest.mock
 import warnings
 
-from test.support import hashlib_helper
+from test.support import hashlib_helper, check_disallow_instantiation
 
 from _operator import _compare_digest as operator_compare_digest
 
@@ -439,11 +439,7 @@ class ConstructorTestCase(unittest.TestCase):
     @unittest.skipUnless(C_HMAC is not None, 'need _hashlib')
     def test_internal_types(self):
         # internal types like _hashlib.C_HMAC are not constructable
-        with self.assertRaisesRegex(
+        check_disallow_instantiation(self, C_HMAC)
-            TypeError, "cannot create '_hashlib.HMAC' instance"
-        ):
-            C_HMAC()
-
         with self.assertRaisesRegex(TypeError, "immutable type"):
             C_HMAC.value = None
 

Lib/test/test_re.py

@@ -1,5 +1,6 @@
 from test.support import (gc_collect, bigmemtest, _2G,
-                          cpython_only, captured_stdout)
+                          cpython_only, captured_stdout,
+                          check_disallow_instantiation)
 import locale
 import re
 import sre_compile
@@ -2218,11 +2219,10 @@ class ImplementationTest(unittest.TestCase):
     @cpython_only
     def test_disallow_instantiation(self):
         # Ensure that the type disallows instantiation (bpo-43916)
-        self.assertRaises(TypeError, re.Match)
+        check_disallow_instantiation(self, re.Match)
-        self.assertRaises(TypeError, re.Pattern)
+        check_disallow_instantiation(self, re.Pattern)
         pat = re.compile("")
-        tp = type(pat.scanner(""))
+        check_disallow_instantiation(self, type(pat.scanner("")))
-        self.assertRaises(TypeError, tp)
 
 
 class ExternalTests(unittest.TestCase):

Lib/test/test_select.py

@@ -88,12 +88,10 @@ class SelectTestCase(unittest.TestCase):
         self.assertEqual(select.select([], a, []), ([], a[:5], []))
 
     def test_disallow_instantiation(self):
-        tp = type(select.poll())
+        support.check_disallow_instantiation(self, type(select.poll()))
-        self.assertRaises(TypeError, tp)
 
         if hasattr(select, 'devpoll'):
-            tp = type(select.devpoll())
+            support.check_disallow_instantiation(self, type(select.devpoll()))
-            self.assertRaises(TypeError, tp)
 
 def tearDownModule():
     support.reap_children()

Lib/test/test_ssl.py

@@ -358,11 +358,7 @@ class BasicSocketTests(unittest.TestCase):
             with self.subTest(ssl_type=ssl_type):
                 with self.assertRaisesRegex(TypeError, "immutable type"):
                     ssl_type.value = None
-        with self.assertRaisesRegex(
+        support.check_disallow_instantiation(self, _ssl.Certificate)
-            TypeError,
-            "cannot create '_ssl.Certificate' instances"
-        ):
-            _ssl.Certificate()
 
     def test_private_init(self):
         with self.assertRaisesRegex(TypeError, "public constructor"):

Lib/test/test_threading.py

@@ -124,8 +124,7 @@ class ThreadTests(BaseTestCase):
     def test_disallow_instantiation(self):
         # Ensure that the type disallows instantiation (bpo-43916)
         lock = threading.Lock()
-        tp = type(lock)
+        test.support.check_disallow_instantiation(self, type(lock))
-        self.assertRaises(TypeError, tp)
 
     # Create a bunch of threads, let each do some work, wait until all are
     # done.

Lib/test/test_unicodedata.py

@@ -12,7 +12,7 @@ import sys
 import unicodedata
 import unittest
 from test.support import (open_urlresource, requires_resource, script_helper,
-                          cpython_only)
+                          cpython_only, check_disallow_instantiation)
 
 
 class UnicodeMethodsTest(unittest.TestCase):
@@ -229,7 +229,7 @@ class UnicodeMiscTest(UnicodeDatabaseTest):
     @cpython_only
     def test_disallow_instantiation(self):
         # Ensure that the type disallows instantiation (bpo-43916)
-        self.assertRaises(TypeError, unicodedata.UCD)
+        check_disallow_instantiation(self, unicodedata.UCD)
 
     def test_failed_import_during_compiling(self):
         # Issue 4367

Lib/test/test_zlib.py

@@ -132,10 +132,8 @@ class ExceptionTestCase(unittest.TestCase):
     @support.cpython_only
     def test_disallow_instantiation(self):
         # Ensure that the type disallows instantiation (bpo-43916)
-        comp_type = type(zlib.compressobj())
+        support.check_disallow_instantiation(self, type(zlib.compressobj()))
-        decomp_type = type(zlib.decompressobj())
+        support.check_disallow_instantiation(self, type(zlib.decompressobj()))
-        self.assertRaises(TypeError, comp_type)
-        self.assertRaises(TypeError, decomp_type)
 
 
 class BaseCompressTestCase(object):