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Fix thread UnraisableException object to be None #8326

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Merged
youknowone merged 1 commit into from
Jul 22, 2026
Merged

Fix thread UnraisableException object to be None #8326

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1 change: 0 additions & 1 deletion Lib/test/test_thread.py
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Original file line number Diff line number Diff line change
Expand Up @@ -151,7 +151,6 @@ def task():
support.gc_collect() # For PyPy or other GCs.
self.assertEqual(thread._count(), orig)

@unittest.expectedFailure # TODO: RUSTPYTHON
def test_unraisable_exception(self):
def task():
started.release()
Expand Down
30 changes: 19 additions & 11 deletions crates/vm/src/stdlib/_thread.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,10 @@ pub(crate) mod _thread {

use crate::{
AsObject, Py, PyPayload, PyRef, PyResult, VirtualMachine,
builtins::{PyDictRef, PyIntRef, PyStr, PyTupleRef, PyType, PyTypeRef, PyUtf8StrRef},
builtins::{
PyBaseExceptionRef, PyDictRef, PyIntRef, PyStr, PyTupleRef, PyType, PyTypeRef,
PyUtf8StrRef,
},
common::wtf8::Wtf8Buf,
frame::FrameRef,
function::{ArgCallable, FuncArgs, KwArgs, OptionalArg, PySetterValue, TimeoutSeconds},
Expand Down Expand Up @@ -558,6 +561,19 @@ pub(crate) mod _thread {
.map_err(|_err| vm.new_runtime_error("can't start new thread"))
}

fn report_unraisable_thread_exception(
exc: PyBaseExceptionRef,
func: &ArgCallable,
vm: &VirtualMachine,
) {
let msg = func
.as_ref()
.repr(vm)
.ok()
.map(|repr| format!("Exception ignored in thread started by {}", repr.as_wtf8()));
vm.run_unraisable(exc, msg, vm.ctx.none());
Comment on lines +569 to +574

@coderabbitai coderabbitai Bot Jul 19, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Handle repr failures gracefully to ensure the context message is printed.

If func.as_ref().repr(vm) fails, ok() maps the result to None, which suppresses the "Exception ignored in thread started by..." context message entirely. CPython prevents this by using a fallback message when the function's representation cannot be retrieved.

🐛 Proposed fix to provide a fallback 
-        let msg = func
-            .as_ref()
-            .repr(vm)
-            .ok()
-            .map(|repr| format!("Exception ignored in thread started by {}", repr.as_wtf8()));
-        vm.run_unraisable(exc, msg, vm.ctx.none());
+        let msg = match func.as_ref().repr(vm) {
+            Ok(repr) => format!("Exception ignored in thread started by {}", repr.as_wtf8()),
+            Err(_) => "Exception ignored in thread started by <function repr() failed>".to_owned(),
+        };
+        vm.run_unraisable(exc, Some(msg), vm.ctx.none());
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
let msg = func
.as_ref()
.repr(vm)
.ok()
.map(|repr| format!("Exception ignored in thread started by {}", repr.as_wtf8()));
vm.run_unraisable(exc, msg, vm.ctx.none());
let msg = match func.as_ref().repr(vm) {
Ok(repr) => format!("Exception ignored in thread started by {}", repr.as_wtf8()),
Err(_) => "Exception ignored in thread started by <function repr() failed>".to_owned(),
};
vm.run_unraisable(exc, Some(msg), vm.ctx.none());
🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@crates/vm/src/stdlib/_thread.rs` around lines 569 - 574, Update the message
construction in the thread exception path around func.as_ref().repr(vm) so repr
failures produce a fallback context string rather than None. Preserve the
existing formatted representation when repr succeeds, and always pass a context
message to vm.run_unraisable.

}

fn run_thread(func: ArgCallable, args: FuncArgs, vm: &VirtualMachine) {
// Increment thread count when thread actually starts executing
vm.state.thread_count.fetch_add(1);
Expand All @@ -572,11 +588,7 @@ pub(crate) mod _thread {
if let Err(exc) = func.invoke(args, vm)
&& !exc.fast_isinstance(vm.ctx.exceptions.system_exit)
{
vm.run_unraisable(
exc,
Some("Exception ignored in thread started by".to_owned()),
func.into(),
);
report_unraisable_thread_exception(exc, &func, vm);
}
}
for lock in SENTINELS.take() {
Expand Down Expand Up @@ -1755,11 +1767,7 @@ pub(crate) mod _thread {
if let Err(exc) = func.invoke((), vm)
&& !exc.fast_isinstance(vm.ctx.exceptions.system_exit)
{
vm.run_unraisable(
exc,
Some("Exception ignored in thread started by".to_owned()),
func.into(),
);
report_unraisable_thread_exception(exc, &func, vm);
}
}
}))
Expand Down
26 changes: 16 additions & 10 deletions crates/vm/src/vm/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1296,18 +1296,24 @@ impl VirtualMachine {
}
};

let msg_str = if let Some(msg) = msg {
format!("{msg}: ")
if self.is_none(object) {
if let Some(msg) = msg {
write_to_stderr(&format!("{msg}:\n"), &stderr, self);
}
} else {
Comment on lines +1299 to 1303

@coderabbitai coderabbitai Bot Jul 19, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Remove the trailing colon when formatting msg without an object.

When object is None, the default unraisable hook should write the message followed by a newline, without a trailing colon. Currently, a thread exception will be incorrectly logged as Exception ignored in thread started by <function>: instead of matching CPython's format.

🐛 Proposed fix 
         if self.is_none(object) {
             if let Some(msg) = msg {
-                write_to_stderr(&format!("{msg}:\n"), &stderr, self);
+                write_to_stderr(&format!("{msg}\n"), &stderr, self);
             }
         } else {
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
if self.is_none(object) {
if let Some(msg) = msg {
write_to_stderr(&format!("{msg}:\n"), &stderr, self);
}
} else {
if self.is_none(object) {
if let Some(msg) = msg {
write_to_stderr(&format!("{msg}\n"), &stderr, self);
}
} else {
🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@crates/vm/src/vm/mod.rs` around lines 1299 - 1303, Update the None-object
branch in the default unraisable hook to write msg followed only by a newline,
removing the trailing colon from the format passed to write_to_stderr. Preserve
the existing conditional behavior and formatting for cases where an object is
present.

"Exception ignored in: ".to_owned()
};
write_to_stderr(&msg_str, &stderr, self);
let msg_str = if let Some(msg) = msg {
format!("{msg}: ")
} else {
"Exception ignored in: ".to_owned()
};
write_to_stderr(&msg_str, &stderr, self);

let repr_result = object.repr(self);
let repr_wtf8 = repr_result
.as_ref()
.map_or_else(|_| "<object repr failed>".as_ref(), |s| s.as_wtf8());
write_to_stderr(&format!("{repr_wtf8}\n"), &stderr, self);
let repr_result = object.repr(self);
let repr_wtf8 = repr_result
.as_ref()
.map_or_else(|_| "<object repr failed>".as_ref(), |s| s.as_wtf8());
write_to_stderr(&format!("{repr_wtf8}\n"), &stderr, self);
}

// Write exception type and message
let exc_type_name = e.class().name();
Expand Down