Add traits for interop fns.

The owned and mut interop traits have the corresponding to/from behaviors on cpp but are defined as empty on upb, while the view interop is implemented for both.

PiperOrigin-RevId: 657617187

rust/codegen_traits.rs

@@ -8,8 +8,10 @@
 //! Traits that are implemeted by codegen types.
 
 use crate::__internal::SealedInternal;
+use crate::__runtime::RawMessage;
 use crate::{MutProxied, MutProxy, ViewProxy};
 use create::Parse;
+use interop::{MessageMutInterop, MessageViewInterop, OwnedMessageInterop};
 use read::Serialize;
 use std::fmt::Debug;
 use write::{Clear, ClearAndParse};
@@ -27,7 +29,10 @@ pub trait Message: SealedInternal
   + Send + Sync
   // Copy/Clone:
   + Clone
-  {}
+  // C++ Interop:
+  + OwnedMessageInterop
+{
+}
 
 /// A trait that all generated message views implement.
 pub trait MessageView<'msg>: SealedInternal
@@ -38,6 +43,8 @@ pub trait MessageView<'msg>: SealedInternal
     + Send + Sync
     // Copy/Clone:
     + Copy + Clone
+    // C++ Interop:
+    + MessageViewInterop<'msg>
 {
     #[doc(hidden)]
     type Message: Message;
@@ -55,6 +62,8 @@ pub trait MessageMut<'msg>: SealedInternal
     + Sync
     // Copy/Clone:
     // (Neither)
+    // C++ Interop:
+    + MessageMutInterop<'msg>
 {
     #[doc(hidden)]
     type Message: Message;
@@ -94,3 +103,77 @@ pub(crate) mod write {
         fn clear_and_parse(&mut self, data: &[u8]) -> Result<(), crate::ParseError>;
     }
 }
+
+/// Traits related to interop with C or C++.
+///
+/// These traits are deliberately not available on the prelude, as they should
+/// be used rarely and with great care.
+pub(crate) mod interop {
+    use super::{RawMessage, SealedInternal};
+
+    /// Traits related to owned message interop. Note that these trait fns
+    /// are only available on C++ kernel as upb interop of owned messages
+    /// requires more work to handle the Arena behavior.
+    pub trait OwnedMessageInterop: SealedInternal {
+        /// Drops `self` and returns the `RawMessage` that it was wrapping
+        /// without deleting it.
+        ///
+        /// The caller is responsible for ensuring the returned RawMessage is
+        /// subsequently deleted (eg by moving it into a std::unique_ptr in
+        /// C++), or else it will leak.
+        #[cfg(cpp_kernel)]
+        fn __unstable_leak_raw_message(self) -> RawMessage;
+
+        /// Takes exclusive ownership of the `raw_message`.
+        ///
+        /// # Safety
+        ///   - The underlying message must be for the same type as `Self`
+        ///   - The pointer passed in must not be used by the caller after being
+        ///     passed here (must not be read, written, or deleted)
+        #[cfg(cpp_kernel)]
+        unsafe fn __unstable_take_ownership_of_raw_message(raw_message: RawMessage) -> Self;
+    }
+
+    /// Traits related to message view interop.
+    pub trait MessageViewInterop<'msg>: SealedInternal {
+        /// Borrows `self` as an underlying `RawMessage`.
+        ///
+        /// Note that the returned Value must be used under the same constraints
+        /// as though it were a borrow of `self`: it should be treated as a
+        /// `const Message*` in C++, and not be mutated in any way, and any
+        /// mutation to the parent message may invalidate it, and it
+        /// must not be deleted.
+        fn __unstable_as_raw_message(&self) -> RawMessage;
+
+        /// Wraps the provided `RawMessage` as a MessageView.
+        ///
+        /// # Safety
+        ///   - The underlying message must be for the same type as `Self`
+        ///   - The underlying message must be alive for 'msg and not mutated
+        ///     while the wrapper is live.
+        unsafe fn __unstable_wrap_raw_message(raw: &'msg RawMessage) -> Self;
+    }
+
+    /// Traits related to message mut interop. Note that these trait fns
+    /// are only available on C++ kernel as upb interop of owned messages
+    /// requires more work to handle the Arena behavior.
+    pub trait MessageMutInterop<'msg>: SealedInternal {
+        /// Exclusive borrows `self` as a `RawMessage`.
+        ///
+        /// Note that the returned Value must be used under the same constraints
+        /// as though it were a mut borrow of `self`: it should be treated as a
+        /// non-owned `Message*` in C++. And any mutation to the parent message
+        /// may invalidate it, and it must not be deleted.
+        #[cfg(cpp_kernel)]
+        fn __unstable_as_raw_message_mut(&mut self) -> RawMessage;
+
+        /// Wraps the provided `RawMessage` as a MessageMut.
+        ///
+        /// # Safety
+        ///   - The underlying message must be for the same type as `Self`
+        ///   - The underlying message must be alive for 'msg and not read or
+        ///     mutated while the wrapper is live.
+        #[cfg(cpp_kernel)]
+        unsafe fn __unstable_wrap_raw_message_mut(raw: &'msg mut RawMessage) -> Self;
+    }
+}

rust/shared.rs

@@ -24,6 +24,7 @@ use std::fmt;
 pub mod __public {
     pub use crate::codegen_traits::{
         create::Parse,
+        interop::{MessageMutInterop, MessageViewInterop, OwnedMessageInterop},
         read::Serialize,
         write::{Clear, ClearAndParse},
         Message, MessageMut, MessageView,

rust/test/cpp/interop/main.rs

@@ -9,6 +9,7 @@ use googletest::prelude::*;
 use protobuf_cpp::prelude::*;
 
 use protobuf_cpp::__runtime::{PtrAndLen, RawMessage};
+use protobuf_cpp::{MessageMutInterop, MessageViewInterop, OwnedMessageInterop};
 use unittest_rust_proto::{TestAllExtensions, TestAllTypes, TestAllTypesMut, TestAllTypesView};
 
 macro_rules! proto_assert_eq {
@@ -39,9 +40,7 @@ extern "C" {
 fn send_to_cpp() {
     let mut msg1 = TestAllTypes::new();
     msg1.set_optional_int32(7);
-    let i = unsafe {
-        TakeOwnershipAndGetOptionalInt32(msg1.__unstable_leak_cpp_repr_grant_permission_to_break())
-    };
+    let i = unsafe { TakeOwnershipAndGetOptionalInt32(msg1.__unstable_leak_raw_message()) };
     assert_eq!(i, 7);
 }
 
@@ -49,7 +48,7 @@ fn send_to_cpp() {
 fn mutate_message_mut_in_cpp() {
     let mut msg1 = TestAllTypes::new();
     unsafe {
-        MutateTestAllTypes(msg1.as_mut().__unstable_cpp_repr_grant_permission_to_break());
+        MutateTestAllTypes(msg1.as_mut().__unstable_as_raw_message_mut());
     }
 
     let mut msg2 = TestAllTypes::new();
@@ -65,9 +64,7 @@ fn deserialize_in_rust() {
     let mut msg1 = TestAllTypes::new();
     msg1.set_optional_int64(-1);
     msg1.set_optional_bytes(b"some cool data I guess");
-    let serialized = unsafe {
-        SerializeTestAllTypes(msg1.as_view().__unstable_cpp_repr_grant_permission_to_break())
-    };
+    let serialized = unsafe { SerializeTestAllTypes(msg1.as_view().__unstable_as_raw_message()) };
 
     let msg2 = TestAllTypes::parse(&serialized).unwrap();
     proto_assert_eq!(msg1, msg2);
@@ -81,7 +78,7 @@ fn deserialize_in_cpp() {
     let data = msg1.serialize().unwrap();
 
     let msg2 = unsafe {
-        TestAllTypes::__unstable_wrap_cpp_grant_permission_to_break(DeserializeTestAllTypes(
+        TestAllTypes::__unstable_take_ownership_of_raw_message(DeserializeTestAllTypes(
             (*data).as_ptr(),
             data.len(),
         ))
@@ -98,7 +95,7 @@ fn deserialize_in_cpp_into_mut() {
     let data = msg1.serialize().unwrap();
 
     let mut raw_msg = unsafe { DeserializeTestAllTypes((*data).as_ptr(), data.len()) };
-    let msg2 = TestAllTypesMut::__unstable_wrap_cpp_grant_permission_to_break(&mut raw_msg);
+    let msg2 = unsafe { TestAllTypesMut::__unstable_wrap_raw_message_mut(&mut raw_msg) };
 
     proto_assert_eq!(msg1, msg2);
 
@@ -116,7 +113,7 @@ fn deserialize_in_cpp_into_view() {
     let data = msg1.serialize().unwrap();
 
     let raw_msg = unsafe { DeserializeTestAllTypes((*data).as_ptr(), data.len()) };
-    let msg2 = TestAllTypesView::__unstable_wrap_cpp_grant_permission_to_break(&raw_msg);
+    let msg2 = unsafe { TestAllTypesView::__unstable_wrap_raw_message(&raw_msg) };
 
     proto_assert_eq!(msg1, msg2);
 
@@ -130,14 +127,12 @@ fn deserialize_in_cpp_into_view() {
 // accidentally get destroyed by Rust.
 #[googletest::test]
 fn smuggle_extension() {
-    let msg1 = unsafe {
-        TestAllExtensions::__unstable_wrap_cpp_grant_permission_to_break(NewWithExtension())
-    };
+    let msg1 =
+        unsafe { TestAllExtensions::__unstable_take_ownership_of_raw_message(NewWithExtension()) };
     let data = msg1.serialize().unwrap();
 
     let mut msg2 = TestAllExtensions::parse(&data).unwrap();
-    let bytes = unsafe {
-        GetBytesExtension(msg2.as_mut().__unstable_cpp_repr_grant_permission_to_break()).as_ref()
-    };
+    let bytes =
+        unsafe { GetBytesExtension(msg2.as_mut().__unstable_as_raw_message_mut()).as_ref() };
     assert_eq!(bytes, b"smuggled");
 }

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

@@ -1287,8 +1287,8 @@ void GenerateRs(Context& ctx, const Descriptor& msg) {
         $nested_in_msg$
       )rs");
 
+  ctx.printer().PrintRaw("\n");
   if (ctx.is_cpp()) {
-    ctx.printer().PrintRaw("\n");
     ctx.Emit({{"Msg", RsSafeName(msg.name())}}, R"rs(
       impl $Msg$ {
         pub fn __unstable_wrap_cpp_grant_permission_to_break(msg: $pbr$::RawMessage) -> Self {
@@ -1299,7 +1299,6 @@ void GenerateRs(Context& ctx, const Descriptor& msg) {
           s.raw_msg()
         }
       }
-
       impl<'a> $Msg$Mut<'a> {
         //~ msg is a &mut so that the borrow checker enforces exclusivity to
         //~ prevent constructing multiple Muts/Views from the same RawMessage.
@@ -1325,9 +1324,58 @@ void GenerateRs(Context& ctx, const Descriptor& msg) {
           self.msg
         }
       }
+
+      impl $pb$::OwnedMessageInterop for $Msg$ {
+        unsafe fn __unstable_take_ownership_of_raw_message(msg: $pbr$::RawMessage) -> Self {
+          Self { inner: $pbr$::MessageInner { msg } }
+        }
+
+        fn __unstable_leak_raw_message(self) -> $pbr$::RawMessage {
+          let s = std::mem::ManuallyDrop::new(self);
+          s.raw_msg()
+        }
+      }
+
+      impl<'a> $pb$::MessageMutInterop<'a> for $Msg$Mut<'a> {
+        unsafe fn __unstable_wrap_raw_message_mut(
+            msg: &'a mut $pbr$::RawMessage) -> Self {
+          Self {
+            inner: $pbr$::MutatorMessageRef::from_raw_msg($pbi$::Private, msg)
+          }
+        }
+        fn __unstable_as_raw_message_mut(&mut self) -> $pbr$::RawMessage {
+          self.raw_msg()
+        }
+      }
+
+      impl<'a> $pb$::MessageViewInterop<'a> for $Msg$View<'a> {
+        unsafe fn __unstable_wrap_raw_message(
+          msg: &'a $pbr$::RawMessage) -> Self {
+          Self::new($pbi$::Private, *msg)
+        }
+        fn __unstable_as_raw_message(&self) -> $pbr$::RawMessage {
+          self.msg
+        }
+      }
+    )rs");
+  } else {
+    ctx.Emit({{"Msg", RsSafeName(msg.name())}}, R"rs(
+      // upb kernel doesn't support any owned message or message mut interop.
+      impl $pb$::OwnedMessageInterop for $Msg$ {}
+      impl<'a> $pb$::MessageMutInterop<'a> for $Msg$Mut<'a> {}
+
+      impl<'a> $pb$::MessageViewInterop<'a> for $Msg$View<'a> {
+        unsafe fn __unstable_wrap_raw_message(
+          msg: &'a $pbr$::RawMessage) -> Self {
+          Self::new($pbi$::Private, *msg)
+        }
+        fn __unstable_as_raw_message(&self) -> $pbr$::RawMessage {
+          self.msg
+        }
+      }
     )rs");
   }
-}
+}  // NOLINT(readability/fn_size)
 
 // Generates code for a particular message in `.pb.thunk.cc`.
 void GenerateThunksCc(Context& ctx, const Descriptor& msg) {