Preserve Expat qualified names without namespace expansion (#9070)

Retain raw element and attribute prefixes when namespace_separator is None. Keep expanded names and parser configuration unchanged, with regression coverage in the pyexpat snippet.

Assisted-by: OpenAI Codex:model identifier unavailable

crates/stdlib/src/pyexpat.rs

@@ -1051,6 +1051,10 @@ mod _pyexpat {
         fn make_name(&self, name: &xml::name::OwnedName) -> String {
             match (&self.namespace_separator, &name.namespace) {
                 (Some(sep), Some(ns)) => format!("{}{}{}", ns, sep, name.local_name),
+                (None, _) => match &name.prefix {
+                    Some(prefix) => format!("{prefix}:{}", name.local_name),
+                    None => name.local_name.clone(),
+                },
                 _ => name.local_name.clone(),
             }
         }

extra_tests/snippets/stdlib_pyexpat.py

@@ -0,0 +1,23 @@
+from xml.parsers import expat
+
+# Without namespace expansion, element and attribute names retain prefixes.
+for separator, expected_name, expected_attribute in (
+    (None, "p:x", "p:a"),
+    ("!", "urn:p!x", "urn:p!a"),
+):
+    for ordered in (False, True):
+        parser = expat.ParserCreate(namespace_separator=separator)
+        parser.ordered_attributes = ordered
+        starts = []
+        ends = []
+        parser.StartElementHandler = lambda name, attrs: starts.append((name, attrs))
+        parser.EndElementHandler = ends.append
+        parser.Parse('<r xmlns:p="urn:p"><p:x p:a="v" a="u"></p:x></r>', True)
+        assert [name for name, attrs in starts] == ["r", expected_name]
+        assert ends == [expected_name, "r"]
+        expected_attributes = (
+            [expected_attribute, "v", "a", "u"]
+            if ordered
+            else {expected_attribute: "v", "a": "u"}
+        )
+        assert starts[1][1] == expected_attributes