Issue #5734: BufferedRWPair was poorly tested and had several glaring bugs.

Patch by Brian Quinlan.

Lib/_pyio.py

@@ -839,7 +839,9 @@ class BufferedReader(_BufferedIOMixin):
     def __init__(self, raw, buffer_size=DEFAULT_BUFFER_SIZE):
         """Create a new buffered reader using the given readable raw IO object.
         """
-        raw._checkReadable()
+        if not raw.readable():
+            raise IOError('"raw" argument must be readable.')
+
         _BufferedIOMixin.__init__(self, raw)
         if buffer_size <= 0:
             raise ValueError("invalid buffer size")
@@ -970,7 +972,9 @@ class BufferedWriter(_BufferedIOMixin):
 
     def __init__(self, raw,
                  buffer_size=DEFAULT_BUFFER_SIZE, max_buffer_size=None):
-        raw._checkWritable()
+        if not raw.writable():
+            raise IOError('"raw" argument must be writable.')
+
         _BufferedIOMixin.__init__(self, raw)
         if buffer_size <= 0:
             raise ValueError("invalid buffer size")
@@ -1076,8 +1080,13 @@ class BufferedRWPair(BufferedIOBase):
         """
         if max_buffer_size is not None:
             warnings.warn("max_buffer_size is deprecated", DeprecationWarning, 2)
-        reader._checkReadable()
+
-        writer._checkWritable()
+        if not reader.readable():
+            raise IOError('"reader" argument must be readable.')
+
+        if not writer.writable():
+            raise IOError('"writer" argument must be writable.')
+
         self.reader = BufferedReader(reader, buffer_size)
         self.writer = BufferedWriter(writer, buffer_size)
 

Lib/test/test_io.py

@@ -1051,13 +1051,11 @@ class PyBufferedWriterTest(BufferedWriterTest):
 
 class BufferedRWPairTest(unittest.TestCase):
 
-    def test_basic(self):
+    def test_constructor(self):
-        r = self.MockRawIO(())
+        pair = self.tp(self.MockRawIO(), self.MockRawIO())
-        w = self.MockRawIO()
-        pair = self.tp(r, w)
         self.assertFalse(pair.closed)
 
-    def test_max_buffer_size_deprecation(self):
+    def test_constructor_max_buffer_size_deprecation(self):
         with support.check_warnings() as w:
             warnings.simplefilter("always", DeprecationWarning)
             self.tp(self.MockRawIO(), self.MockRawIO(), 8, 12)
@@ -1067,7 +1065,100 @@ class BufferedRWPairTest(unittest.TestCase):
             self.assertEqual(str(warning.message),
                              "max_buffer_size is deprecated")
 
-        # XXX More Tests
+    def test_constructor_with_not_readable(self):
+        class NotReadable(MockRawIO):
+            def readable(self):
+                return False
+
+        self.assertRaises(IOError, self.tp, NotReadable(), self.MockRawIO())
+
+    def test_constructor_with_not_writeable(self):
+        class NotWriteable(MockRawIO):
+            def writable(self):
+                return False
+
+        self.assertRaises(IOError, self.tp, self.MockRawIO(), NotWriteable())
+
+    def test_read(self):
+        pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
+
+        self.assertEqual(pair.read(3), b"abc")
+        self.assertEqual(pair.read(1), b"d")
+        self.assertEqual(pair.read(), b"ef")
+
+    def test_read1(self):
+        # .read1() is delegated to the underlying reader object, so this test
+        # can be shallow.
+        pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
+
+        self.assertEqual(pair.read1(3), b"abc")
+
+    def test_readinto(self):
+        pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
+
+        data = bytearray(5)
+        self.assertEqual(pair.readinto(data), 5)
+        self.assertEqual(data, b"abcde")
+
+    def test_write(self):
+        w = self.MockRawIO()
+        pair = self.tp(self.MockRawIO(), w)
+
+        pair.write(b"abc")
+        pair.flush()
+        pair.write(b"def")
+        pair.flush()
+        self.assertEqual(w._write_stack, [b"abc", b"def"])
+
+    def test_peek(self):
+        pair = self.tp(self.BytesIO(b"abcdef"), self.MockRawIO())
+
+        self.assertTrue(pair.peek(3).startswith(b"abc"))
+        self.assertEqual(pair.read(3), b"abc")
+
+    def test_readable(self):
+        pair = self.tp(self.MockRawIO(), self.MockRawIO())
+        self.assertTrue(pair.readable())
+
+    def test_writeable(self):
+        pair = self.tp(self.MockRawIO(), self.MockRawIO())
+        self.assertTrue(pair.writable())
+
+    def test_seekable(self):
+        # BufferedRWPairs are never seekable, even if their readers and writers
+        # are.
+        pair = self.tp(self.MockRawIO(), self.MockRawIO())
+        self.assertFalse(pair.seekable())
+
+    # .flush() is delegated to the underlying writer object and has been
+    # tested in the test_write method.
+
+    def test_close_and_closed(self):
+        pair = self.tp(self.MockRawIO(), self.MockRawIO())
+        self.assertFalse(pair.closed)
+        pair.close()
+        self.assertTrue(pair.closed)
+
+    def test_isatty(self):
+        class SelectableIsAtty(MockRawIO):
+            def __init__(self, isatty):
+                MockRawIO.__init__(self)
+                self._isatty = isatty
+
+            def isatty(self):
+                return self._isatty
+
+        pair = self.tp(SelectableIsAtty(False), SelectableIsAtty(False))
+        self.assertFalse(pair.isatty())
+
+        pair = self.tp(SelectableIsAtty(True), SelectableIsAtty(False))
+        self.assertTrue(pair.isatty())
+
+        pair = self.tp(SelectableIsAtty(False), SelectableIsAtty(True))
+        self.assertTrue(pair.isatty())
+
+        pair = self.tp(SelectableIsAtty(True), SelectableIsAtty(True))
+        self.assertTrue(pair.isatty())
 
 class CBufferedRWPairTest(BufferedRWPairTest):
     tp = io.BufferedRWPair

Misc/NEWS

@@ -72,6 +72,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #5734: BufferedRWPair was poorly tested and had several glaring
+  bugs. Patch by Brian Quinlan.
+
 - Issue #1161031: fix readwrite select flag handling: POLLPRI now
   results in a handle_expt_event call, not handle_read_event, and POLLERR
   and POLLNVAL now call handle_close, not handle_expt_event.  Also,

Modules/_io/bufferedio.c

@@ -1846,7 +1846,7 @@ typedef struct {
 
 static int
 BufferedRWPair_init(BufferedRWPairObject *self, PyObject *args,
-                     PyObject *kwds)
+                    PyObject *kwds)
 {
     PyObject *reader, *writer;
     Py_ssize_t buffer_size = DEFAULT_BUFFER_SIZE;
@@ -1865,29 +1865,18 @@ BufferedRWPair_init(BufferedRWPairObject *self, PyObject *args,
     if (_PyIOBase_checkWritable(writer, Py_True) == NULL)
         return -1;
 
-    args = Py_BuildValue("(n)", buffer_size);
+    self->reader = (BufferedObject *) PyObject_CallFunction(
-    if (args == NULL) {
+            (PyObject *) &PyBufferedReader_Type, "On", reader, buffer_size);
-        Py_CLEAR(self->reader);
-        return -1;
-    }
-    self->reader = (BufferedObject *)PyType_GenericNew(
-            &PyBufferedReader_Type, args, NULL);
-    Py_DECREF(args);
     if (self->reader == NULL)
         return -1;
 
-    args = Py_BuildValue("(n)", buffer_size);
+    self->writer = (BufferedObject *) PyObject_CallFunction(
-    if (args == NULL) {
+            (PyObject *) &PyBufferedWriter_Type, "On", writer, buffer_size);
-        Py_CLEAR(self->reader);
-        return -1;
-    }
-    self->writer = (BufferedObject *)PyType_GenericNew(
-            &PyBufferedWriter_Type, args, NULL);
-    Py_DECREF(args);
     if (self->writer == NULL) {
         Py_CLEAR(self->reader);
         return -1;
     }
+
     return 0;
 }
 
@@ -1951,6 +1940,12 @@ BufferedRWPair_read1(BufferedRWPairObject *self, PyObject *args)
     return _forward_call(self->reader, "read1", args);
 }
 
+static PyObject *
+BufferedRWPair_readinto(BufferedRWPairObject *self, PyObject *args)
+{
+    return _forward_call(self->reader, "readinto", args);
+}
+
 static PyObject *
 BufferedRWPair_write(BufferedRWPairObject *self, PyObject *args)
 {
@@ -2000,12 +1995,17 @@ BufferedRWPair_isatty(BufferedRWPairObject *self, PyObject *args)
     return _forward_call(self->reader, "isatty", args);
 }
 
+static PyObject *
+BufferedRWPair_closed_get(BufferedRWPairObject *self, void *context)
+{
+    return PyObject_GetAttr((PyObject *) self->writer, _PyIO_str_closed);
+}
 
 static PyMethodDef BufferedRWPair_methods[] = {
     {"read", (PyCFunction)BufferedRWPair_read, METH_VARARGS},
     {"peek", (PyCFunction)BufferedRWPair_peek, METH_VARARGS},
     {"read1", (PyCFunction)BufferedRWPair_read1, METH_VARARGS},
-    {"readinto", (PyCFunction)Buffered_readinto, METH_VARARGS},
+    {"readinto", (PyCFunction)BufferedRWPair_readinto, METH_VARARGS},
 
     {"write", (PyCFunction)BufferedRWPair_write, METH_VARARGS},
     {"flush", (PyCFunction)BufferedRWPair_flush, METH_NOARGS},
@@ -2019,6 +2019,11 @@ static PyMethodDef BufferedRWPair_methods[] = {
     {NULL, NULL}
 };
 
+static PyGetSetDef BufferedRWPair_getset[] = {
+    {"closed", (getter)BufferedRWPair_closed_get, NULL, NULL},
+    {0}
+};
+
 PyTypeObject PyBufferedRWPair_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)
     "_io.BufferedRWPair",       /*tp_name*/
@@ -2050,7 +2055,7 @@ PyTypeObject PyBufferedRWPair_Type = {
     0,                          /* tp_iternext */
     BufferedRWPair_methods,     /* tp_methods */
     0,                          /* tp_members */
-    0,                          /* tp_getset */
+    BufferedRWPair_getset,      /* tp_getset */
     0,                          /* tp_base */
     0,                          /* tp_dict */
     0,                          /* tp_descr_get */