allow more operations to work on detached streams (closes #23093)

Patch by Martin Panter.

Lib/_pyio.py

@@ -775,7 +775,7 @@ class _BufferedIOMixin(BufferedIOBase):
         clsname = self.__class__.__name__
         try:
             name = self.name
-        except AttributeError:
+        except Exception:
             return "<_pyio.{0}>".format(clsname)
         else:
             return "<_pyio.{0} name={1!r}>".format(clsname, name)
@@ -1538,7 +1538,7 @@ class TextIOWrapper(TextIOBase):
     def __repr__(self):
         try:
             name = self.name
-        except AttributeError:
+        except Exception:
             return "<_pyio.TextIOWrapper encoding='{0}'>".format(self.encoding)
         else:
             return "<_pyio.TextIOWrapper name={0!r} encoding='{1}'>".format(

Lib/test/test_io.py

@@ -654,6 +654,8 @@ class CommonBufferedTests:
         self.assertIs(buf.detach(), raw)
         self.assertRaises(ValueError, buf.detach)
 
+        repr(buf)  # Should still work
+
     def test_fileno(self):
         rawio = self.MockRawIO()
         bufio = self.tp(rawio)
@@ -1922,6 +1924,12 @@ class TextIOWrapperTest(unittest.TestCase):
         self.assertEqual(r.getvalue(), b"howdy")
         self.assertRaises(ValueError, t.detach)
 
+        # Operations independent of the detached stream should still work
+        repr(t)
+        self.assertEqual(t.encoding, "ascii")
+        self.assertEqual(t.errors, "strict")
+        self.assertFalse(t.line_buffering)
+
     def test_repr(self):
         raw = self.BytesIO("hello".encode("utf-8"))
         b = self.BufferedReader(raw)
@@ -1936,6 +1944,9 @@ class TextIOWrapperTest(unittest.TestCase):
         self.assertEqual(repr(t),
                          "<%s.TextIOWrapper name='dummy' encoding='utf-8'>" % modname)
 
+        t.buffer.detach()
+        repr(t)  # Should not raise an exception
+
     def test_line_buffering(self):
         r = self.BytesIO()
         b = self.BufferedWriter(r, 1000)
@@ -2537,6 +2548,9 @@ class CTextIOWrapperTest(TextIOWrapperTest):
         self.assertRaises(ValueError, t.__init__, b, newline='xyzzy')
         self.assertRaises(ValueError, t.read)
 
+        t = self.TextIOWrapper.__new__(self.TextIOWrapper)
+        self.assertRaises(Exception, repr, t)
+
     def test_garbage_collection(self):
         # C TextIOWrapper objects are collected, and collecting them flushes
         # all data to disk.

Misc/NEWS

@@ -15,6 +15,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #23093: In the io, module allow more operations to work on detached
+  streams.
+
 - Issue #23071: Added missing names to codecs.__all__.  Patch by Martin Panter.
 
 - Issue #23016: A warning no longer produces an AttributeError when sys.stderr

Modules/_io/bufferedio.c

@@ -1222,7 +1222,7 @@ buffered_repr(buffered *self)
 
     nameobj = PyObject_GetAttrString((PyObject *) self, "name");
     if (nameobj == NULL) {
-        if (PyErr_ExceptionMatches(PyExc_AttributeError))
+        if (PyErr_ExceptionMatches(PyExc_Exception))
             PyErr_Clear();
         else
             return NULL;

Modules/_io/textio.c

@@ -1152,25 +1152,27 @@ textiowrapper_closed_get(textio *self, void *context);
 
 #define CHECK_INITIALIZED(self) \
     if (self->ok <= 0) { \
-        if (self->detached) { \
-            PyErr_SetString(PyExc_ValueError, \
-                 "underlying buffer has been detached"); \
-        } else {                                   \
-            PyErr_SetString(PyExc_ValueError, \
-                "I/O operation on uninitialized object"); \
-        } \
+        PyErr_SetString(PyExc_ValueError, \
+            "I/O operation on uninitialized object"); \
+        return NULL; \
+    }
+
+#define CHECK_ATTACHED(self) \
+    CHECK_INITIALIZED(self); \
+    if (self->detached) { \
+        PyErr_SetString(PyExc_ValueError, \
+             "underlying buffer has been detached"); \
         return NULL; \
     }
 
-#define CHECK_INITIALIZED_INT(self) \
+#define CHECK_ATTACHED_INT(self) \
     if (self->ok <= 0) { \
-        if (self->detached) { \
-            PyErr_SetString(PyExc_ValueError, \
-                 "underlying buffer has been detached"); \
-        } else {                                   \
-            PyErr_SetString(PyExc_ValueError, \
-                "I/O operation on uninitialized object"); \
-        } \
+        PyErr_SetString(PyExc_ValueError, \
+            "I/O operation on uninitialized object"); \
+        return -1; \
+    } else if (self->detached) { \
+        PyErr_SetString(PyExc_ValueError, \
+             "underlying buffer has been detached"); \
         return -1; \
     }
 
@@ -1179,7 +1181,7 @@ static PyObject *
 textiowrapper_detach(textio *self)
 {
     PyObject *buffer, *res;
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     res = PyObject_CallMethodObjArgs((PyObject *)self, _PyIO_str_flush, NULL);
     if (res == NULL)
         return NULL;
@@ -1187,7 +1189,6 @@ textiowrapper_detach(textio *self)
     buffer = self->buffer;
     self->buffer = NULL;
     self->detached = 1;
-    self->ok = 0;
     return buffer;
 }
 
@@ -1244,7 +1245,7 @@ textiowrapper_write(textio *self, PyObject *args)
     int haslf = 0;
     int needflush = 0;
 
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
 
     if (!PyArg_ParseTuple(args, "U:write", &text)) {
         return NULL;
@@ -1486,7 +1487,7 @@ textiowrapper_read(textio *self, PyObject *args)
     Py_ssize_t n = -1;
     PyObject *result = NULL, *chunks = NULL;
 
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
 
     if (!PyArg_ParseTuple(args, "|O&:read", &_PyIO_ConvertSsize_t, &n))
         return NULL;
@@ -1849,7 +1850,7 @@ textiowrapper_readline(textio *self, PyObject *args)
     PyObject *limitobj = NULL;
     Py_ssize_t limit = -1;
 
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     if (!PyArg_ParseTuple(args, "|O:readline", &limitobj)) {
         return NULL;
     }
@@ -2004,7 +2005,7 @@ textiowrapper_seek(textio *self, PyObject *args)
     PyObject *res;
     int cmp;
 
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
 
     if (!PyArg_ParseTuple(args, "O|i:seek", &cookieObj, &whence))
         return NULL;
@@ -2189,7 +2190,7 @@ textiowrapper_tell(textio *self, PyObject *args)
     PyObject *saved_state = NULL;
     char *input, *input_end;
 
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     CHECK_CLOSED(self);
 
     if (!self->seekable) {
@@ -2353,7 +2354,7 @@ textiowrapper_truncate(textio *self, PyObject *args)
     PyObject *pos = Py_None;
     PyObject *res;
 
-    CHECK_INITIALIZED(self)
+    CHECK_ATTACHED(self)
     if (!PyArg_ParseTuple(args, "|O:truncate", &pos)) {
         return NULL;
     }
@@ -2376,7 +2377,7 @@ textiowrapper_repr(textio *self)
 
     nameobj = PyObject_GetAttrString((PyObject *) self, "name");
     if (nameobj == NULL) {
-        if (PyErr_ExceptionMatches(PyExc_AttributeError))
+        if (PyErr_ExceptionMatches(PyExc_Exception))
             PyErr_Clear();
         else
             goto error;
@@ -2408,42 +2409,42 @@ error:
 static PyObject *
 textiowrapper_fileno(textio *self, PyObject *args)
 {
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     return PyObject_CallMethod(self->buffer, "fileno", NULL);
 }
 
 static PyObject *
 textiowrapper_seekable(textio *self, PyObject *args)
 {
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     return PyObject_CallMethod(self->buffer, "seekable", NULL);
 }
 
 static PyObject *
 textiowrapper_readable(textio *self, PyObject *args)
 {
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     return PyObject_CallMethod(self->buffer, "readable", NULL);
 }
 
 static PyObject *
 textiowrapper_writable(textio *self, PyObject *args)
 {
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     return PyObject_CallMethod(self->buffer, "writable", NULL);
 }
 
 static PyObject *
 textiowrapper_isatty(textio *self, PyObject *args)
 {
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     return PyObject_CallMethod(self->buffer, "isatty", NULL);
 }
 
 static PyObject *
 textiowrapper_flush(textio *self, PyObject *args)
 {
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     CHECK_CLOSED(self);
     self->telling = self->seekable;
     if (_textiowrapper_writeflush(self) < 0)
@@ -2456,7 +2457,7 @@ textiowrapper_close(textio *self, PyObject *args)
 {
     PyObject *res;
     int r;
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
 
     res = textiowrapper_closed_get(self, NULL);
     if (res == NULL)
@@ -2498,7 +2499,7 @@ textiowrapper_iternext(textio *self)
 {
     PyObject *line;
 
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
 
     self->telling = 0;
     if (Py_TYPE(self) == &PyTextIOWrapper_Type) {
@@ -2534,14 +2535,14 @@ textiowrapper_iternext(textio *self)
 static PyObject *
 textiowrapper_name_get(textio *self, void *context)
 {
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     return PyObject_GetAttrString(self->buffer, "name");
 }
 
 static PyObject *
 textiowrapper_closed_get(textio *self, void *context)
 {
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     return PyObject_GetAttr(self->buffer, _PyIO_str_closed);
 }
 
@@ -2549,7 +2550,7 @@ static PyObject *
 textiowrapper_newlines_get(textio *self, void *context)
 {
     PyObject *res;
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     if (self->decoder == NULL)
         Py_RETURN_NONE;
     res = PyObject_GetAttr(self->decoder, _PyIO_str_newlines);
@@ -2576,7 +2577,7 @@ textiowrapper_errors_get(textio *self, void *context)
 static PyObject *
 textiowrapper_chunk_size_get(textio *self, void *context)
 {
-    CHECK_INITIALIZED(self);
+    CHECK_ATTACHED(self);
     return PyLong_FromSsize_t(self->chunk_size);
 }
 
@@ -2584,7 +2585,7 @@ static int
 textiowrapper_chunk_size_set(textio *self, PyObject *arg, void *context)
 {
     Py_ssize_t n;
-    CHECK_INITIALIZED_INT(self);
+    CHECK_ATTACHED_INT(self);
     n = PyNumber_AsSsize_t(arg, PyExc_TypeError);
     if (n == -1 && PyErr_Occurred())
         return -1;