gh-111942: Fix crashes in TextIOWrapper.reconfigure() (GH-111976)

* Fix crash when encoding is not string or None.
* Fix crash when both line_buffering and write_through raise exception
  when converted ti int.
* Add a number of tests for constructor and reconfigure() method
  with invalid arguments.

Lib/test/test_io.py

@@ -77,6 +77,10 @@ requires_alarm = unittest.skipUnless(
 )
 
 
+class BadIndex:
+    def __index__(self):
+        1/0
+
 class MockRawIOWithoutRead:
     """A RawIO implementation without read(), so as to exercise the default
     RawIO.read() which calls readinto()."""
@@ -2709,8 +2713,31 @@ class TextIOWrapperTest(unittest.TestCase):
         self.assertEqual(t.encoding, "utf-8")
         self.assertEqual(t.line_buffering, True)
         self.assertEqual("\xe9\n", t.readline())
-        self.assertRaises(TypeError, t.__init__, b, encoding="utf-8", newline=42)
-        self.assertRaises(ValueError, t.__init__, b, encoding="utf-8", newline='xyzzy')
+        invalid_type = TypeError if self.is_C else ValueError
+        with self.assertRaises(invalid_type):
+            t.__init__(b, encoding=42)
+        with self.assertRaises(UnicodeEncodeError):
+            t.__init__(b, encoding='\udcfe')
+        with self.assertRaises(ValueError):
+            t.__init__(b, encoding='utf-8\0')
+        with self.assertRaises(invalid_type):
+            t.__init__(b, encoding="utf-8", errors=42)
+        if support.Py_DEBUG or sys.flags.dev_mode or self.is_C:
+            with self.assertRaises(UnicodeEncodeError):
+                t.__init__(b, encoding="utf-8", errors='\udcfe')
+        if support.Py_DEBUG or sys.flags.dev_mode:
+            # TODO: If encoded to UTF-8, should also be checked for
+            # embedded null characters.
+            with self.assertRaises(ValueError):
+                t.__init__(b, encoding="utf-8", errors='replace\0')
+        with self.assertRaises(TypeError):
+            t.__init__(b, encoding="utf-8", newline=42)
+        with self.assertRaises(ValueError):
+            t.__init__(b, encoding="utf-8", newline='\udcfe')
+        with self.assertRaises(ValueError):
+            t.__init__(b, encoding="utf-8", newline='\n\0')
+        with self.assertRaises(ValueError):
+            t.__init__(b, encoding="utf-8", newline='xyzzy')
 
     def test_uninitialized(self):
         t = self.TextIOWrapper.__new__(self.TextIOWrapper)
@@ -3756,6 +3783,59 @@ class TextIOWrapperTest(unittest.TestCase):
 
         self.assertEqual(txt.detach().getvalue(), b'LF\nCRLF\r\n')
 
+    def test_reconfigure_errors(self):
+        txt = self.TextIOWrapper(self.BytesIO(), 'ascii', 'replace', '\r')
+        with self.assertRaises(TypeError):  # there was a crash
+            txt.reconfigure(encoding=42)
+        if self.is_C:
+            with self.assertRaises(UnicodeEncodeError):
+                txt.reconfigure(encoding='\udcfe')
+            with self.assertRaises(LookupError):
+                txt.reconfigure(encoding='locale\0')
+        # TODO: txt.reconfigure(encoding='utf-8\0')
+        # TODO: txt.reconfigure(encoding='nonexisting')
+        with self.assertRaises(TypeError):
+            txt.reconfigure(errors=42)
+        if self.is_C:
+            with self.assertRaises(UnicodeEncodeError):
+                txt.reconfigure(errors='\udcfe')
+        # TODO: txt.reconfigure(errors='ignore\0')
+        # TODO: txt.reconfigure(errors='nonexisting')
+        with self.assertRaises(TypeError):
+            txt.reconfigure(newline=42)
+        with self.assertRaises(ValueError):
+            txt.reconfigure(newline='\udcfe')
+        with self.assertRaises(ValueError):
+            txt.reconfigure(newline='xyz')
+        if not self.is_C:
+            # TODO: Should fail in C too.
+            with self.assertRaises(ValueError):
+                txt.reconfigure(newline='\n\0')
+        if self.is_C:
+            # TODO: Use __bool__(), not __index__().
+            with self.assertRaises(ZeroDivisionError):
+                txt.reconfigure(line_buffering=BadIndex())
+            with self.assertRaises(OverflowError):
+                txt.reconfigure(line_buffering=2**1000)
+            with self.assertRaises(ZeroDivisionError):
+                txt.reconfigure(write_through=BadIndex())
+            with self.assertRaises(OverflowError):
+                txt.reconfigure(write_through=2**1000)
+            with self.assertRaises(ZeroDivisionError):  # there was a crash
+                txt.reconfigure(line_buffering=BadIndex(),
+                                write_through=BadIndex())
+        self.assertEqual(txt.encoding, 'ascii')
+        self.assertEqual(txt.errors, 'replace')
+        self.assertIs(txt.line_buffering, False)
+        self.assertIs(txt.write_through, False)
+
+        txt.reconfigure(encoding='latin1', errors='ignore', newline='\r\n',
+                        line_buffering=True, write_through=True)
+        self.assertEqual(txt.encoding, 'latin1')
+        self.assertEqual(txt.errors, 'ignore')
+        self.assertIs(txt.line_buffering, True)
+        self.assertIs(txt.write_through, True)
+
     def test_reconfigure_newline(self):
         raw = self.BytesIO(b'CR\rEOF')
         txt = self.TextIOWrapper(raw, 'ascii', newline='\n')
@@ -4781,9 +4861,11 @@ def load_tests(loader, tests, pattern):
         if test.__name__.startswith("C"):
             for name, obj in c_io_ns.items():
                 setattr(test, name, obj)
+            test.is_C = True
         elif test.__name__.startswith("Py"):
             for name, obj in py_io_ns.items():
                 setattr(test, name, obj)
+            test.is_C = False
 
     suite = loader.suiteClass()
     for test in tests: