From 1eed0f968f5f44d6a13403c1676298a322cbfbad Mon Sep 17 00:00:00 2001
From: sobolevn <mail@sobolevn.me>
Date: Mon, 26 Aug 2024 21:59:50 +0300
Subject: [PATCH] gh-123340: Show string value of `IS_OP` oparg in `dis`
 (#123348)

---
 Lib/dis.py                                               | 3 +++
 Lib/test/test_dis.py                                     | 9 +++++++++
 .../2024-08-26-19-36-00.gh-issue-123340.mQKI1H.rst       | 1 +
 3 files changed, 13 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2024-08-26-19-36-00.gh-issue-123340.mQKI1H.rst

diff --git a/Lib/dis.py b/Lib/dis.py
index 077c4035ca6..bdac296e9c7 100644
--- a/Lib/dis.py
+++ b/Lib/dis.py
@@ -51,6 +51,7 @@ LOAD_SPECIAL = opmap['LOAD_SPECIAL']
 LOAD_FAST_LOAD_FAST = opmap['LOAD_FAST_LOAD_FAST']
 STORE_FAST_LOAD_FAST = opmap['STORE_FAST_LOAD_FAST']
 STORE_FAST_STORE_FAST = opmap['STORE_FAST_STORE_FAST']
+IS_OP = opmap['IS_OP']
 
 CACHE = opmap["CACHE"]
 
@@ -629,6 +630,8 @@ class ArgResolver:
                     argrepr = repr(obj)
             elif deop == LOAD_SPECIAL:
                 argrepr = _special_method_names[arg]
+            elif deop == IS_OP:
+                argrepr = 'is not' if argval else 'is'
         return argval, argrepr
 
 def get_instructions(x, *, first_line=None, show_caches=None, adaptive=False):
diff --git a/Lib/test/test_dis.py b/Lib/test/test_dis.py
index db69bc7ccdc..ab0fcee747d 100644
--- a/Lib/test/test_dis.py
+++ b/Lib/test/test_dis.py
@@ -2028,6 +2028,15 @@ class InstructionTests(InstructionTestCase):
         dis.dis(f.__code__, file=output, show_caches=True)
         self.assertIn("L1:", output.getvalue())
 
+    def test_is_op_format(self):
+        output = io.StringIO()
+        dis.dis("a is b", file=output, show_caches=True)
+        self.assertIn("IS_OP                    0 (is)", output.getvalue())
+
+        output = io.StringIO()
+        dis.dis("a is not b", file=output, show_caches=True)
+        self.assertIn("IS_OP                    1 (is not)", output.getvalue())
+
     def test_baseopname_and_baseopcode(self):
         # Standard instructions
         for name, code in dis.opmap.items():
diff --git a/Misc/NEWS.d/next/Library/2024-08-26-19-36-00.gh-issue-123340.mQKI1H.rst b/Misc/NEWS.d/next/Library/2024-08-26-19-36-00.gh-issue-123340.mQKI1H.rst
new file mode 100644
index 00000000000..8a462b23004
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-08-26-19-36-00.gh-issue-123340.mQKI1H.rst
@@ -0,0 +1 @@
+Show string value of :opcode:`IS_OP` oparg in :mod:`dis` output.