From 24b63c695ae0a95b06379eaadace66735abac1e2 Mon Sep 17 00:00:00 2001
From: Dong-hee Na <donghee.na@python.org>
Date: Mon, 23 Aug 2021 10:01:51 +0000
Subject: [PATCH] bpo-24234: Implement bytes.__bytes__ (GH-27901)

---
 Doc/whatsnew/3.11.rst                         |  8 ++++++++
 Lib/test/test_bytes.py                        | 12 +++++++++++
 Lib/test/test_typing.py                       |  2 +-
 .../2021-08-23-10-36-55.bpo-24234.MGVUQi.rst  |  3 +++
 Objects/bytesobject.c                         | 20 +++++++++++++++++++
 Objects/clinic/bytesobject.c.h                | 20 ++++++++++++++++++-
 Tools/clinic/clinic.py                        |  1 -
 7 files changed, 63 insertions(+), 3 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2021-08-23-10-36-55.bpo-24234.MGVUQi.rst

diff --git a/Doc/whatsnew/3.11.rst b/Doc/whatsnew/3.11.rst
index cb8f84c4b62..306385c2a90 100644
--- a/Doc/whatsnew/3.11.rst
+++ b/Doc/whatsnew/3.11.rst
@@ -169,6 +169,14 @@ Other Language Changes
   (Contributed by Serhiy Storchaka in :issue:`12022`.)
 
 
+Other CPython Implementation Changes
+====================================
+
+* Special methods :meth:`complex.__complex__` and :meth:`bytes.__bytes__` are implemented to
+  support :class:`typing.SupportsComplex` and :class:`typing.SupportsBytes` protocols.
+  (Contributed by Mark Dickinson and Dong-hee Na in :issue:`24234`.)
+
+
 New Modules
 ===========
 
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
index 13ad238242d..c45c69f3f22 100644
--- a/Lib/test/test_bytes.py
+++ b/Lib/test/test_bytes.py
@@ -981,6 +981,18 @@ class BaseBytesTest:
 class BytesTest(BaseBytesTest, unittest.TestCase):
     type2test = bytes
 
+    def test__bytes__(self):
+        foo = b'foo'
+        self.assertEqual(foo.__bytes__(), foo)
+        self.assertEqual(type(foo.__bytes__()), self.type2test)
+
+        class bytes_subclass(bytes):
+            pass
+
+        bar = bytes_subclass(b'bar')
+        self.assertEqual(bar.__bytes__(), bar)
+        self.assertEqual(type(bar.__bytes__()), self.type2test)
+
     def test_getitem_error(self):
         b = b'python'
         msg = "byte indices must be integers or slices"
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index 84521ee7dd9..de4db51bdc7 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -1543,11 +1543,11 @@ class ProtocolTests(BaseTestCase):
 
     def test_supports_bytes(self):
 
-        # Note: bytes itself doesn't have __bytes__.
         class B:
             def __bytes__(self):
                 return b''
 
+        self.assertIsSubclass(bytes, typing.SupportsBytes)
         self.assertIsSubclass(B, typing.SupportsBytes)
         self.assertNotIsSubclass(str, typing.SupportsBytes)
 
diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-08-23-10-36-55.bpo-24234.MGVUQi.rst b/Misc/NEWS.d/next/Core and Builtins/2021-08-23-10-36-55.bpo-24234.MGVUQi.rst
new file mode 100644
index 00000000000..3f724da0889
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2021-08-23-10-36-55.bpo-24234.MGVUQi.rst	
@@ -0,0 +1,3 @@
+Implement the :meth:`__bytes__` special method on the :class:`bytes` type,
+so a bytes object ``b``  passes an ``isinstance(b, typing.SupportsBytes)``
+check.
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index eaedb0b5689..13f94b4c82f 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -1687,6 +1687,25 @@ static PyBufferProcs bytes_as_buffer = {
 };
 
 
+/*[clinic input]
+bytes.__bytes__
+Convert this value to exact type bytes.
+[clinic start generated code]*/
+
+static PyObject *
+bytes___bytes___impl(PyBytesObject *self)
+/*[clinic end generated code: output=63a306a9bc0caac5 input=34ec5ddba98bd6bb]*/
+{
+    if (PyBytes_CheckExact(self)) {
+        Py_INCREF(self);
+        return (PyObject *)self;
+    }
+    else {
+        return PyBytes_FromString(self->ob_sval);
+    }
+}
+
+
 #define LEFTSTRIP 0
 #define RIGHTSTRIP 1
 #define BOTHSTRIP 2
@@ -2474,6 +2493,7 @@ bytes_getnewargs(PyBytesObject *v, PyObject *Py_UNUSED(ignored))
 static PyMethodDef
 bytes_methods[] = {
     {"__getnewargs__",          (PyCFunction)bytes_getnewargs,  METH_NOARGS},
+    BYTES___BYTES___METHODDEF
     {"capitalize", stringlib_capitalize, METH_NOARGS,
      _Py_capitalize__doc__},
     STRINGLIB_CENTER_METHODDEF
diff --git a/Objects/clinic/bytesobject.c.h b/Objects/clinic/bytesobject.c.h
index 9e365ce1a08..103a3642813 100644
--- a/Objects/clinic/bytesobject.c.h
+++ b/Objects/clinic/bytesobject.c.h
@@ -2,6 +2,24 @@
 preserve
 [clinic start generated code]*/
 
+PyDoc_STRVAR(bytes___bytes____doc__,
+"__bytes__($self, /)\n"
+"--\n"
+"\n"
+"Convert this value to exact type bytes.");
+
+#define BYTES___BYTES___METHODDEF    \
+    {"__bytes__", (PyCFunction)bytes___bytes__, METH_NOARGS, bytes___bytes____doc__},
+
+static PyObject *
+bytes___bytes___impl(PyBytesObject *self);
+
+static PyObject *
+bytes___bytes__(PyBytesObject *self, PyObject *Py_UNUSED(ignored))
+{
+    return bytes___bytes___impl(self);
+}
+
 PyDoc_STRVAR(bytes_split__doc__,
 "split($self, /, sep=None, maxsplit=-1)\n"
 "--\n"
@@ -878,4 +896,4 @@ skip_optional_pos:
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=b3f0ec2753246b9c input=a9049054013a1b77]*/
+/*[clinic end generated code: output=d706344859f40122 input=a9049054013a1b77]*/
diff --git a/Tools/clinic/clinic.py b/Tools/clinic/clinic.py
index ed17fabf8d2..b5a884536a9 100755
--- a/Tools/clinic/clinic.py
+++ b/Tools/clinic/clinic.py
@@ -2179,7 +2179,6 @@ unsupported_special_methods = set("""
 __abs__
 __add__
 __and__
-__bytes__
 __call__
 __delitem__
 __divmod__