Implement _opt for messages

Add convenience _opt for singular message fields.
Users can detect if the message is set or unset, and unwrap via into_inner.

PiperOrigin-RevId: 602749065

rust/test/shared/BUILD

@@ -363,11 +363,15 @@ rust_test(
 rust_test(
     name = "simple_nested_cpp_test",
     srcs = ["simple_nested_test.rs"],
+    aliases = {
+        "//rust:protobuf_cpp": "protobuf",
+    },
     tags = [
         # TODO: Enable testing on arm once we support sanitizers for Rust on Arm.
         "not_build:arm",
     ],
     deps = [
+        "//rust:protobuf_cpp",
         "//rust/test:nested_cc_rust_proto",
         "@crate_index//:googletest",
     ],
@@ -376,11 +380,15 @@ rust_test(
 rust_test(
     name = "simple_nested_upb_test",
     srcs = ["simple_nested_test.rs"],
+    aliases = {
+        "//rust:protobuf_upb": "protobuf",
+    },
     tags = [
         # TODO: Enable testing on arm once we support sanitizers for Rust on Arm.
         "not_build:arm",
     ],
     deps = [
+        "//rust:protobuf_upb",
         "//rust/test:nested_upb_rust_proto",
         "@crate_index//:googletest",
     ],

rust/test/shared/accessors_test.rs

@@ -680,6 +680,26 @@ fn test_singular_msg_field() {
     assert_that!(msg_mut.bb(), eq(0));
 }
 
+#[test]
+fn test_message_opt() {
+    let msg = TestAllTypes::new();
+    let opt: Optional<
+        unittest_proto::TestAllTypes_::NestedMessageView<'_>,
+        unittest_proto::TestAllTypes_::NestedMessageView<'_>,
+    > = msg.optional_nested_message_opt();
+    assert_that!(opt.is_set(), eq(false));
+    assert_that!(opt.into_inner().bb(), eq(0));
+}
+
+#[test]
+fn test_message_opt_set() {
+    let mut msg = TestAllTypes::new();
+    //let opt = msg.optional_nested_message_mut().or_default();
+    //assert_that!(opt.is_set(), eq(false));
+    //todo: check for set after prereq cl
+    //assert_that!(opt.into_inner().bb(), eq(0));
+}
+
 #[test]
 fn test_optional_nested_enum_accessors() {
     use TestAllTypes_::NestedEnum;

rust/test/shared/simple_nested_test.rs

@@ -10,6 +10,7 @@ use nested_proto::Outer_::InnerMut;
 use nested_proto::Outer_::InnerView;
 use nested_proto::Outer_::Inner_::InnerEnum;
 use nested_proto::*;
+use protobuf::Optional;
 
 #[test]
 fn test_deeply_nested_message() {

src/google/protobuf/compiler/rust/accessors/singular_message.cc

@@ -89,6 +89,18 @@ void SingularMessage::InMsgImpl(Context& ctx, const FieldDescriptor& field,
                 }
                 )rs");
              }},
+            {"getter_opt",
+             [&] {
+               ctx.Emit({}, R"rs(
+                pub fn $field$_opt($view_self$) ->
+                $pb$::Optional<$msg_type$View<$view_lifetime$>> {
+                  let view = self.$field$();
+                  $pb$::Optional::new(view, unsafe {
+                    $hazzer_thunk$(self.raw_msg())
+                  })
+            }
+            )rs");
+             }},
             {"clearer",
              [&] {
                if (accessor_case == AccessorCase::VIEW) {
@@ -102,6 +114,7 @@ void SingularMessage::InMsgImpl(Context& ctx, const FieldDescriptor& field,
            R"rs(
             $getter$
             $getter_mut$
+            $getter_opt$
             $clearer$
         )rs");
 }