Make the oneof view accessors use consuming-self and the corresponding longer lifetime, avoiding unnecessary shortening of lifetimes in some cases.

This follows the precedent established on other accessors on Msg Views.

PiperOrigin-RevId: 614658415

rust/test/shared/accessors_proto3_test.rs

@@ -273,15 +273,10 @@ fn test_oneof_accessors() {
     assert_that!(msg.oneof_uint32_opt(), eq(Optional::Unset(0)));
     assert_that!(msg.oneof_field(), matches_pattern!(not_set(_)));
 
-    // TODO: the submessage api is still in progress so we can't yet
-    // cause a submsg to be set here.
+    msg.oneof_nested_message_mut().or_default(); // Cause the nested_message field to become set.
 
-    // msg.oneof_nested_message_mut().or_default(); // Cause the nested_message
-    // field to become set.
-
-    // assert_that!(msg.oneof_bytes_opt(),
-    // eq(Optional::Unset(_))); assert_that!(msg.oneof_field(),
-    // matches_pattern!(OneofNestedMessage(_)));
+    assert_that!(msg.oneof_bytes_opt(), matches_pattern!(Optional::Unset(_)));
+    assert_that!(msg.oneof_field(), matches_pattern!(OneofNestedMessage(_)));
 
     msg.set_oneof_uint32(7);
     msg.set_oneof_bytes(b"123");
@@ -292,6 +287,22 @@ fn test_oneof_accessors() {
     assert_that!(msg.oneof_field(), matches_pattern!(not_set(_)));
 }
 
+#[test]
+fn test_oneof_accessors_view_long_lifetime() {
+    use TestAllTypes_::OneofField::*;
+
+    let mut msg = TestAllTypes::new();
+    msg.set_oneof_uint32(7);
+
+    // The oneof-view accessor on MsgViews should maintain the longest lifetime (can
+    // outlive the message view).
+    let oneof = {
+        let view = msg.as_view();
+        view.oneof_field()
+    };
+    assert_that!(oneof, matches_pattern!(OneofUint32(eq(7))));
+}
+
 #[test]
 fn test_oneof_enum_accessors() {
     use unittest_proto3::{

src/google/protobuf/compiler/rust/oneof.cc

@@ -235,6 +235,8 @@ void GenerateOneofAccessors(Context& ctx, const OneofDescriptor& oneof,
                             AccessorCase accessor_case) {
   ctx.Emit(
       {{"oneof_name", RsSafeName(oneof.name())},
+       {"view_lifetime", ViewLifetime(accessor_case)},
+       {"view_self", ViewReceiver(accessor_case)},
        {"view_enum_name", OneofViewEnumRsName(oneof)},
        {"mut_enum_name", OneofMutEnumRsName(oneof)},
        {"case_enum_name", OneofCaseEnumRsName(oneof)},
@@ -293,7 +295,7 @@ void GenerateOneofAccessors(Context& ctx, const OneofDescriptor& oneof,
        {"getter",
         [&] {
           ctx.Emit({}, R"rs(
-          pub fn $oneof_name$(&self) -> $Msg$_::$view_enum_name$ {
+          pub fn $oneof_name$($view_self$) -> $Msg$_::$view_enum_name$<$view_lifetime$> {
             match unsafe { $case_thunk$(self.raw_msg()) } {
               $view_cases$
               _ => $Msg$_::$view_enum_name$::not_set(std::marker::PhantomData)