Skip to content

Fix locals()/vars() cell-variable sync for module/class scope #8467

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
youknowone merged 1 commit into from
Aug 8, 2026
+54 −3
Merged

Fix locals()/vars() cell-variable sync for module/class scope #8467

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 4 additions & 3 deletions crates/vm/src/frame.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1794,9 +1794,10 @@ impl FrameObject {
}
}

// Free variables only included for optimized (function-like) scopes.
// Class/module scopes should not expose free vars in locals().
if kind == CO_FAST_FREE && !is_optimized {
// CPython only syncs fastlocals/cells into locals() for function
// scope; class/module scope just returns the namespace dict as-is
// (_PyFrame_GetLocals, Objects/frameobject.c).
if !is_optimized && kind & (CO_FAST_CELL | CO_FAST_FREE) != 0 {
continue;
}

Expand Down
50 changes: 50 additions & 0 deletions extra_tests/snippets/syntax_annotations_locals.py
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,50 @@
"""Module/class-scope locals() must not corrupt or leak __conditional_annotations__.

CPython's _PyFrame_GetLocals never syncs cell variables into a module/class
scope's namespace dict, it just returns the dict directly (verified against
CPython 3.14.6). __conditional_annotations__ is a cell in both scopes, but
only module codegen also writes it into the dict (StoreName); class codegen
only ever uses the cell (StoreDeref). So it's visible via locals()/dir() at
module scope and absent at class scope.

RustPython's fast-locals-to-mapping sync used to read every cellvar's value
straight from the cell regardless of scope. At module scope the cell is
always empty, so this overwrote the dict's real value with None -- deleting
it, and the next annotated statement raised NameError. At class scope it
leaked __conditional_annotations__ into locals()/dir(), which CPython never
does.
"""

count: int = 1
_ = locals()
maybe: int = None # used to raise NameError before the fix
assert maybe is None

assert "__conditional_annotations__" in dir(), (
"module-level annotation should expose __conditional_annotations__, matching CPython"
)

exec("a: int = 1\nlocals()\nb: int = 2")

if True:
x: int = 1
vars()
if True:
y: int = 2
assert (x, y) == (1, 2)


class C:
if True:
cx: int = 1
locals()
if True:
cy: int = 2
assert "__conditional_annotations__" not in dir(), (
"class-level locals() should not leak __conditional_annotations__, matching CPython"
)


assert (C.cx, C.cy) == (1, 2)

print("ok")
Loading