Parsing the with statement with tuple argument failed

[15r10nk]

Describe the bug

The following code can not be parsed/formatted by black:

with (name_2, name_2) as name_2:
    pass

black reported the following error:

> black -l 100 -t py312 bug.py
error: cannot format bug.py: INTERNAL ERROR: Black 25.1.1.dev21+g944a38e.d20250317 on Python (CPython) 3
.12.6 produced code that is not equivalent to the source.  Please report a bug on https://github.com/psf
/black/issues.  This diff might be helpful: /tmp/blk_umh51eiz.log

Oh no! 💥 💔 💥
1 file failed to reformat.

the reported diff in /tmp/blk_umh51eiz.log is:

--- src
+++ dst
@@ -5,30 +5,29 @@
         Pass(
         )  # /Pass
         items=
         withitem(
             context_expr=
-            Tuple(
+            Name(
                 ctx=
                 Load(
                 )  # /Load
-                elts=
-                Name(
-                    ctx=
-                    Load(
-                    )  # /Load
-                    id=
-                    'name_2',  # str
-                )  # /Name
-                Name(
-                    ctx=
-                    Load(
-                    )  # /Load
-                    id=
-                    'name_2',  # str
-                )  # /Name
-            )  # /Tuple
+                id=
+                'name_2',  # str
+            )  # /Name
+            optional_vars=
+            None,  # NoneType
+        )  # /withitem
+        withitem(
+            context_expr=
+            Name(
+                ctx=
+                Load(
+                )  # /Load
+                id=
+                'name_2',  # str
+            )  # /Name
             optional_vars=
             Name(
                 ctx=
                 Store(
                 )  # /Store

but it can be parsed by cpython:

from ast import parse
parse(
    'with (name_2, name_2) as name_2:\n'
    '    pass\n'
)

result:

returncode: 0

Environment

• Black's version: current main (6144c46)
• OS and Python version: Linux/Python 3.12.6 (main, Sep 9 2024, 22:11:19) [Clang 18.1.8 ]

Additional context

The bug was found by pysource-codegen (see #3908)
The above problem description was created from a script, let me know if you think it can be improved.

[tusharsadhwani]

What I'm surprised by is that this didn't get caught by primer. Fix should be easy though, thanks again for doing your part, the fuzzer is going to help so much going forward.

[JelleZijlstra]

This is purely theoretical because it's always a runtime error (tuples don't support the context manager protocol). Still good to fix of course.

[15r10nk]

This is purely theoretical

Yes, but I have no choice. pysource-codegen generates its own test cases, which means it would find it if I try to create an exception here. Generating these cases is the best I can do here.

[JelleZijlstra]

Yes, that makes sense and I'm grateful that you're doing this; I was replying to Tushar's comment about primer not finding it.