bpo-25455: Fixed crashes in repr of recursive buffered file-like obje…

Lib/test/test_fileio.py

@@ -10,7 +10,7 @@
 from functools import wraps
 
 from test.support import (TESTFN, TESTFN_UNICODE, check_warnings, run_unittest,
-                          make_bad_fd, cpython_only)
+                          make_bad_fd, cpython_only, swap_attr)
 from collections import UserList
 
 import _io  # C implementation of io
@@ -176,6 +176,12 @@ def testReprNoCloseFD(self):
         finally:
             os.close(fd)
 
+    def testRecursiveRepr(self):
+        # Issue #25455
+        with swap_attr(self.f, 'name', self.f):
+            with self.assertRaises(RuntimeError):
+                repr(self.f)  # Should not crash
+
     def testErrors(self):
         f = self.f
         self.assertFalse(f.isatty())

Lib/test/test_io.py

@@ -1014,6 +1014,16 @@ def test_repr(self):
         raw.name = b"dummy"
         self.assertEqual(repr(b), "<%s name=b'dummy'>" % clsname)
 
+    def test_recursive_repr(self):
+        # Issue #25455
+        raw = self.MockRawIO()
+        b = self.tp(raw)
+        with support.swap_attr(raw, 'name', b):
+            try:
+                repr(b)  # Should not crash
+            except RuntimeError:
+                pass
+
     def test_flush_error_on_close(self):
         # Test that buffered file is closed despite failed flush
         # and that flush() is called before file closed.
@@ -2424,6 +2434,16 @@ def test_repr(self):
         t.buffer.detach()
         repr(t)  # Should not raise an exception
 
+    def test_recursive_repr(self):
+        # Issue #25455
+        raw = self.BytesIO()
+        t = self.TextIOWrapper(raw)
+        with support.swap_attr(raw, 'name', t):
+            try:
+                repr(t)  # Should not crash
+            except RuntimeError:
+                pass
+
     def test_line_buffering(self):
         r = self.BytesIO()
         b = self.BufferedWriter(r, 1000)