#16518: Bring error messages in harmony with docs ("bytes-like object")

Some time ago we changed the docs to consistently use the term 'bytes-like
object' in all the contexts where bytes, bytearray, memoryview, etc are used.
This patch (by Ezio Melotti) completes that work by changing the error
messages that previously reported that certain types did "not support the
buffer interface" to instead say that a bytes-like object is required.  (The
glossary entry for bytes-like object references the discussion of the buffer
protocol in the docs.)

Doc/whatsnew/3.5.rst

@@ -393,6 +393,12 @@ Changes in the Python API
   The *convert_charrefs* argument of :class:`~html.parser.HTMLParser` is
   now ``True`` by default (contributed by Berker Peksag in :issue:`21047`).
 
+* Although it is not formally part of the API, it is worth noting for porting
+  purposes (ie: fixing tests) that error messages that were previously of the
+  form "'sometype' does not support the buffer protocol" are now of the form "a
+  bytes-like object is required, not 'sometype'" (contributed by Ezio Melotti
+  in :issue:`16518`).
+
 Changes in the C API
 --------------------
 

Lib/test/test_socket.py

@@ -711,11 +711,11 @@ class GeneralModuleTests(unittest.TestCase):
         with self.assertRaises(TypeError) as cm:
             s.sendto('\u2620', sockname)
         self.assertEqual(str(cm.exception),
-                         "'str' does not support the buffer interface")
+                         "a bytes-like object is required, not 'str'")
         with self.assertRaises(TypeError) as cm:
             s.sendto(5j, sockname)
         self.assertEqual(str(cm.exception),
-                         "'complex' does not support the buffer interface")
+                         "a bytes-like object is required, not 'complex'")
         with self.assertRaises(TypeError) as cm:
             s.sendto(b'foo', None)
         self.assertIn('not NoneType',str(cm.exception))
@@ -723,11 +723,11 @@ class GeneralModuleTests(unittest.TestCase):
         with self.assertRaises(TypeError) as cm:
             s.sendto('\u2620', 0, sockname)
         self.assertEqual(str(cm.exception),
-                         "'str' does not support the buffer interface")
+                         "a bytes-like object is required, not 'str'")
         with self.assertRaises(TypeError) as cm:
             s.sendto(5j, 0, sockname)
         self.assertEqual(str(cm.exception),
-                         "'complex' does not support the buffer interface")
+                         "a bytes-like object is required, not 'complex'")
         with self.assertRaises(TypeError) as cm:
             s.sendto(b'foo', 0, None)
         self.assertIn('not NoneType', str(cm.exception))

Misc/NEWS

@@ -10,6 +10,10 @@ Release date: TBA
 Core and Builtins
 -----------------
 
+- Issue #16518: Use 'bytes-like object required' in error messages that
+  previously used the far more cryptic "'x' does not support the buffer
+  protocol.
+
 - Issue #22470: Fixed integer overflow issues in "backslashreplace",
   "xmlcharrefreplace", and "surrogatepass" error handlers.
 

Modules/_operator.c

@@ -241,7 +241,7 @@ PyDoc_STRVAR(compare_digest__doc__,
 "Return 'a == b'.  This function uses an approach designed to prevent\n"
 "timing analysis, making it appropriate for cryptography.\n"
 "a and b must both be of the same type: either str (ASCII only),\n"
-"or any type that supports the buffer protocol (e.g. bytes).\n"
+"or any bytes-like object.\n"
 "\n"
 "Note: If a and b are of different lengths, or if an error occurs,\n"
 "a timing attack could theoretically reveal information about the\n"

Objects/abstract.c

@@ -260,8 +260,7 @@ PyObject_AsCharBuffer(PyObject *obj,
     pb = obj->ob_type->tp_as_buffer;
     if (pb == NULL || pb->bf_getbuffer == NULL) {
         PyErr_SetString(PyExc_TypeError,
-                        "expected bytes, bytearray "
+                        "expected a bytes-like object");
-                        "or buffer compatible object");
         return -1;
     }
     if ((*pb->bf_getbuffer)(obj, &view, PyBUF_SIMPLE)) return -1;
@@ -306,7 +305,7 @@ int PyObject_AsReadBuffer(PyObject *obj,
     if (pb == NULL ||
         pb->bf_getbuffer == NULL) {
         PyErr_SetString(PyExc_TypeError,
-                        "expected an object with a buffer interface");
+                        "expected a bytes-like object");
         return -1;
     }
 
@@ -336,7 +335,7 @@ int PyObject_AsWriteBuffer(PyObject *obj,
         pb->bf_getbuffer == NULL ||
         ((*pb->bf_getbuffer)(obj, &view, PyBUF_WRITABLE) != 0)) {
         PyErr_SetString(PyExc_TypeError,
-                        "expected an object with a writable buffer interface");
+                        "expected a writable bytes-like object");
         return -1;
     }
 
@@ -355,7 +354,7 @@ PyObject_GetBuffer(PyObject *obj, Py_buffer *view, int flags)
 {
     if (!PyObject_CheckBuffer(obj)) {
         PyErr_Format(PyExc_TypeError,
-                     "'%.100s' does not support the buffer interface",
+                     "a bytes-like object is required, not '%.100s'",
                      Py_TYPE(obj)->tp_name);
         return -1;
     }
@@ -530,8 +529,8 @@ int PyObject_CopyData(PyObject *dest, PyObject *src)
     if (!PyObject_CheckBuffer(dest) ||
         !PyObject_CheckBuffer(src)) {
         PyErr_SetString(PyExc_TypeError,
-                        "both destination and source must have the "\
+                        "both destination and source must be "\
-                        "buffer interface");
+                        "bytes-like objects");
         return -1;
     }
 

Objects/bytearrayobject.c

@@ -87,7 +87,7 @@ _getbuffer(PyObject *obj, Py_buffer *view)
     if (buffer == NULL || buffer->bf_getbuffer == NULL)
     {
         PyErr_Format(PyExc_TypeError,
-                     "Type %.100s doesn't support the buffer API",
+                     "a bytes-like object is required, not '%.100s'",
                      Py_TYPE(obj)->tp_name);
         return -1;
     }

Objects/bytes_methods.c

@@ -371,7 +371,7 @@ _getbuffer(PyObject *obj, Py_buffer *view)
     if (buffer == NULL || buffer->bf_getbuffer == NULL)
     {
         PyErr_Format(PyExc_TypeError,
-                     "Type %.100s doesn't support the buffer API",
+                     "a bytes-like object is required, not '%.100s'",
                      Py_TYPE(obj)->tp_name);
         return -1;
     }

Objects/bytesobject.c

@@ -29,7 +29,7 @@ _getbuffer(PyObject *obj, Py_buffer *view)
     if (bufferprocs == NULL || bufferprocs->bf_getbuffer == NULL)
     {
         PyErr_Format(PyExc_TypeError,
-                     "Type %.100s doesn't support the buffer API",
+                     "a bytes-like object is required, not '%.100s'",
                      Py_TYPE(obj)->tp_name);
         return -1;
     }

Objects/longobject.c

@@ -4873,9 +4873,7 @@ PyDoc_STRVAR(long_from_bytes_doc,
 \n\
 Return the integer represented by the given array of bytes.\n\
 \n\
-The bytes argument must either support the buffer protocol or be an\n\
+The bytes argument must be a bytes-like object (e.g. bytes or bytearray).\n\
-iterable object producing bytes.  Bytes and bytearray are examples of\n\
-built-in objects that support the buffer protocol.\n\
 \n\
 The byteorder argument determines the byte order used to represent the\n\
 integer.  If byteorder is 'big', the most significant byte is at the\n\

Objects/memoryobject.c

@@ -792,7 +792,7 @@ PyMemoryView_FromObject(PyObject *v)
     }
 
     PyErr_Format(PyExc_TypeError,
-        "memoryview: %.200s object does not have the buffer interface",
+        "memoryview: a bytes-like object is required, not '%.200s'",
         Py_TYPE(v)->tp_name);
     return NULL;
 }

Python/getargs.c

@@ -1244,7 +1244,8 @@ convertsimple(PyObject *arg, const char **p_format, va_list *p_va, int flags,
            supports it directly. */
         if (PyObject_GetBuffer(arg, (Py_buffer*)p, PyBUF_WRITABLE) < 0) {
             PyErr_Clear();
-            return converterr("read-write buffer", arg, msgbuf, bufsize);
+            return converterr("read-write bytes-like object",
+                              arg, msgbuf, bufsize);
         }
         if (!PyBuffer_IsContiguous((Py_buffer*)p, 'C')) {
             PyBuffer_Release((Py_buffer*)p);
@@ -1282,7 +1283,7 @@ convertbuffer(PyObject *arg, void **p, char **errmsg)
     *errmsg = NULL;
     *p = NULL;
     if (pb != NULL && pb->bf_releasebuffer != NULL) {
-        *errmsg = "read-only pinned buffer";
+        *errmsg = "read-only bytes-like object";
         return -1;
     }
 
@@ -1298,7 +1299,7 @@ static int
 getbuffer(PyObject *arg, Py_buffer *view, char **errmsg)
 {
     if (PyObject_GetBuffer(arg, view, PyBUF_SIMPLE) != 0) {
-        *errmsg = "bytes or buffer";
+        *errmsg = "bytes-like object";
         return -1;
     }
     if (!PyBuffer_IsContiguous(view, 'C')) {