gh-142594: fix by property calls io.TextIOWrapper.detach

Lib/test/test_io/test_textio.py

@@ -1544,6 +1544,22 @@ def write(self, data):
         self.assertEqual([b"abcdef", b"middle", b"g"*chunk_size],
                          buf._write_stack)
 
+    def test_issue142594(self):
+        wrapper = None
+        detached = False
+        class ReentrantRawIO(self.RawIOBase):
+            @property
+            def closed(self):
+                nonlocal detached
+                if wrapper is not None and not detached:
+                    detached = True
+                    wrapper.detach()
+                return False
+
+        raw = ReentrantRawIO()
+        wrapper = self.TextIOWrapper(raw)
+        wrapper.close()  # should not crash
+
 
 class PyTextIOWrapperTest(TextIOWrapperTest, PyTestCase):
     shutdown_error = "LookupError: unknown encoding: ascii"

Misc/NEWS.d/next/Library/2025-12-14-18-30-48.gh-issue-142594.belDmD.rst

@@ -0,0 +1,2 @@
+Fix crash in ``TextIOWrapper.close()`` when the underlying buffer's
+``closed`` property calls ``TextIOWrapper.detach()``.

Modules/_io/textio.c

@@ -3150,6 +3150,9 @@ _io_TextIOWrapper_close_impl(textio *self)
     if (r > 0) {
         Py_RETURN_NONE; /* stream already closed */
     }
+    if (self->detached) {
+        Py_RETURN_NONE; /* gh-142594 null pointer issue */
+    }
     else {
         PyObject *exc = NULL;
         if (self->finalizing) {