Fix debug_test to work with C++ lite

This change adds a cfg attribute 'cpp_lite' to the C++ kernel of Protobuf Rust. If C++ lite is selected on the command line, the cfg attribute 'cpp_lite' is set. The root cause of the test failure was that the Debug implementation for full C++ protos uses  text proto which is not available in C++ lite. The fix uses the 'cpp_lite' cfg attribute to select a different Debug implementation that doesn't rely on text proto

PiperOrigin-RevId: 640552701

rust/cpp.rs

@@ -228,12 +228,17 @@ impl From<RustStringRawParts> for String {
 
 extern "C" {
     fn utf8_debug_string(msg: RawMessage) -> RustStringRawParts;
+    fn utf8_debug_string_lite(msg: RawMessage) -> RustStringRawParts;
 }
 
 pub fn debug_string(_private: Private, msg: RawMessage, f: &mut fmt::Formatter<'_>) -> fmt::Result {
     // SAFETY:
     // - `msg` is a valid protobuf message.
+    #[cfg(not(lite_runtime))]
     let dbg_str: String = unsafe { utf8_debug_string(msg) }.into();
+    #[cfg(lite_runtime)]
+    let dbg_str: String = unsafe { utf8_debug_string_lite(msg) }.into();
+
     write!(f, "{dbg_str}")
 }
 

rust/cpp_kernel/cpp_api.cc

@@ -7,6 +7,7 @@
 
 #include "google/protobuf/map.h"
 #include "google/protobuf/message.h"
+#include "google/protobuf/message_lite.h"
 #include "google/protobuf/repeated_field.h"
 #include "google/protobuf/repeated_ptr_field.h"
 
@@ -141,6 +142,12 @@ google::protobuf::rust_internal::RustStringRawParts utf8_debug_string(
   std::string text = google::protobuf::Utf8Format(*msg);
   return google::protobuf::rust_internal::RustStringRawParts(text);
 }
+
+google::protobuf::rust_internal::RustStringRawParts utf8_debug_string_lite(
+    const google::protobuf::MessageLite* msg) {
+  std::string text = google::protobuf::Utf8Format(*msg);
+  return google::protobuf::rust_internal::RustStringRawParts(text);
+}
 }
 
 namespace google {

rust/cpp_kernel/cpp_api.h

@@ -179,6 +179,8 @@ struct RustStringRawParts {
 };
 
 extern "C" RustStringRawParts utf8_debug_string(const google::protobuf::Message* msg);
+extern "C" RustStringRawParts utf8_debug_string_lite(
+    const google::protobuf::MessageLite* msg);
 }  // namespace rust_internal
 }  // namespace protobuf
 }  // namespace google

rust/test/cpp/debug_test.rs

@@ -1,6 +1,7 @@
 use debug_rust_proto::DebugMsg;
 use googletest::prelude::*;
 
+#[cfg(not(lite_runtime))]
 #[test]
 fn test_debug() {
     let mut msg = DebugMsg::new();
@@ -10,3 +11,14 @@ fn test_debug() {
     assert_that!(format!("{msg:?}"), contains_substring("id: 1"));
     assert_that!(format!("{msg:?}"), not(contains_substring("password")));
 }
+
+#[cfg(lite_runtime)]
+#[test]
+fn test_debug_lite() {
+    let mut msg = DebugMsg::new();
+    msg.set_id(1);
+    msg.set_secret_user_data("password");
+
+    assert_that!(format!("{msg:?}"), contains_substring("MessageLite"));
+    assert_that!(format!("{msg:?}"), not(contains_substring("password")));
+}