[Python-checkins] bpo-46361: Fix "small" `int` caching (GH-30583)

[mdickinson]

https://github.com/python/cpython/commit/5cd9a162cd02a3d0f1b0a182d80feeb17439e84f
commit: 5cd9a162cd02a3d0f1b0a182d80feeb17439e84f
branch: main
author: Brandt Bucher <brandt at python.org>
committer: mdickinson <dickinsm at gmail.com>
date: 2022-01-16T16:06:37Z
summary:

bpo-46361: Fix "small" `int` caching (GH-30583)

files:
A Misc/NEWS.d/next/Core and Builtins/2022-01-12-17-15-17.bpo-46361.mgI_j_.rst
M Lib/test/test_decimal.py
M Lib/test/test_long.py
M Modules/_decimal/_decimal.c
M Objects/longobject.c

diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index b6173a5ffec96..9ced801afc2e9 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -2552,6 +2552,13 @@ def test_int(self):
         self.assertRaises(OverflowError, int, Decimal('inf'))
         self.assertRaises(OverflowError, int, Decimal('-inf'))
 
+    @cpython_only
+    def test_small_ints(self):
+        Decimal = self.decimal.Decimal
+        # bpo-46361
+        for x in range(-5, 257):
+            self.assertIs(int(Decimal(x)), x)
+
     def test_trunc(self):
         Decimal = self.decimal.Decimal
 
diff --git a/Lib/test/test_long.py b/Lib/test/test_long.py
index f2a622b5868f0..c7dd0b274d1e3 100644
--- a/Lib/test/test_long.py
+++ b/Lib/test/test_long.py
@@ -1471,6 +1471,13 @@ def __init__(self, value):
         self.assertEqual(i, 1)
         self.assertEqual(getattr(i, 'foo', 'none'), 'bar')
 
+    @support.cpython_only
+    def test_from_bytes_small(self):
+        # bpo-46361
+        for i in range(-5, 257):
+            b = i.to_bytes(2, signed=True)
+            self.assertIs(int.from_bytes(b, signed=True), i)
+
     def test_access_to_nonexistent_digit_0(self):
         # http://bugs.python.org/issue14630: A bug in _PyLong_Copy meant that
         # ob_digit[0] was being incorrectly accessed for instances of a
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-01-12-17-15-17.bpo-46361.mgI_j_.rst b/Misc/NEWS.d/next/Core and Builtins/2022-01-12-17-15-17.bpo-46361.mgI_j_.rst
new file mode 100644
index 0000000000000..eef877d5cbd8f
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-01-12-17-15-17.bpo-46361.mgI_j_.rst	
@@ -0,0 +1,2 @@
+Ensure that "small" integers created by :meth:`int.from_bytes` and
+:class:`decimal.Decimal` are properly cached.
diff --git a/Modules/_decimal/_decimal.c b/Modules/_decimal/_decimal.c
index 7fc7315603e7a..35a115676a71b 100644
--- a/Modules/_decimal/_decimal.c
+++ b/Modules/_decimal/_decimal.c
@@ -3394,6 +3394,13 @@ dec_as_long(PyObject *dec, PyObject *context, int round)
         return NULL;
     }
 
+    if (n == 1) {
+        sdigit val = mpd_arith_sign(x) * ob_digit[0];
+        mpd_free(ob_digit);
+        mpd_del(x);
+        return PyLong_FromLong(val);
+    }
+
     assert(n > 0);
     pylong = _PyLong_New(n);
     if (pylong == NULL) {
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 5d181aa0850aa..1b2d1266c6bc5 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -911,7 +911,7 @@ _PyLong_FromByteArray(const unsigned char* bytes, size_t n,
     }
 
     Py_SET_SIZE(v, is_signed ? -idigit : idigit);
-    return (PyObject *)long_normalize(v);
+    return (PyObject *)maybe_small_long(long_normalize(v));
 }
 
 int