BaseException.__setstate__ (#5821)

* docs

* BaseException.__setstate__

Lib/test/support/__init__.py

@@ -1933,8 +1933,7 @@ def _check_tracemalloc():
                                      "if tracemalloc module is tracing "
                                      "memory allocations")
 
-
-# TODO: RUSTPYTHON (comment out before)
+# TODO: RUSTPYTHON; GC is not supported yet
 # def check_free_after_iterating(test, iter, cls, args=()):
 #     class A(cls):
 #         def __del__(self):

Lib/test/test_array.py

@@ -176,7 +176,7 @@ class ArrayReconstructorTest(unittest.TestCase):
                 self.assertEqual(a, b,
                     msg="{0!r} != {1!r}; testcase={2!r}".format(a, b, testcase))
 
-    # TODO: RUSTPYTHON
+    # TODO: RUSTPYTHON - requires UTF-32 encoding support in codecs and proper array reconstructor implementation
     @unittest.expectedFailure
     def test_unicode(self):
         teststr = "Bonne Journ\xe9e \U0002030a\U00020347"

Lib/test/test_baseexception.py

@@ -83,7 +83,7 @@ class ExceptionClassTests(unittest.TestCase):
         exc_set = set(e for e in exc_set if not e.startswith('_'))
         # RUSTPYTHON specific
         exc_set.discard("JitError")
-        # TODO: RUSTPYTHON; this will be officially introduced in Python 3.15
+        # XXX: RUSTPYTHON; IncompleteInputError will be officially introduced in Python 3.15
         exc_set.discard("IncompleteInputError")
         self.assertEqual(len(exc_set), 0, "%s not accounted for" % exc_set)
 
@@ -121,8 +121,6 @@ class ExceptionClassTests(unittest.TestCase):
                 [repr(exc), exc.__class__.__name__ + '()'])
         self.interface_test_driver(results)
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_setstate_refcount_no_crash(self):
         # gh-97591: Acquire strong reference before calling tp_hash slot
         # in PyObject_SetAttr.

vm/src/exceptions.rs

@@ -647,6 +647,24 @@ impl PyRef<PyBaseException> {
             vm.new_tuple((self.class().to_owned(), self.args()))
         }
     }
+
+    #[pymethod(magic)]
+    fn setstate(self, state: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyObjectRef> {
+        if !vm.is_none(&state) {
+            let dict = state
+                .downcast::<crate::builtins::PyDict>()
+                .map_err(|_| vm.new_type_error("state is not a dictionary".to_owned()))?;
+
+            for (key, value) in &dict {
+                let key_str = key.str(vm)?;
+                if key_str.as_str().starts_with("__") {
+                    continue;
+                }
+                self.as_object().set_attr(&key_str, value.clone(), vm)?;
+            }
+        }
+        Ok(vm.ctx.none())
+    }
 }
 
 impl Constructor for PyBaseException {