GH-47429: [C++] Fix Flight Symbol Visibility on Windows

Author: WillAyd

.github/workflows/cpp.yml

@@ -300,7 +300,7 @@ jobs:
       ARROW_BUILD_STATIC: OFF
       ARROW_BUILD_TESTS: ON
       ARROW_DATASET: ON
-      ARROW_FLIGHT: OFF
+      ARROW_FLIGHT: ON
       ARROW_HDFS: ON
       ARROW_HOME: /usr
       ARROW_JEMALLOC: OFF

cpp/src/arrow/flight/CMakeLists.txt

@@ -104,10 +104,23 @@ set(FLIGHT_PROTOC_COMMAND ${ARROW_PROTOBUF_PROTOC} "-I${FLIGHT_PROTO_PATH}")
 if(Protobuf_VERSION VERSION_LESS 3.15)
   list(APPEND FLIGHT_PROTOC_COMMAND "--experimental_allow_proto3_optional")
 endif()
+
+if(MSVC)
+  if(ARROW_BUILD_STATIC)
+    set(FLIGHT_PROTOC_VISIBILITY "")
+  else()
+    set(FLIGHT_PROTOC_VISIBILITY "dllexport_decl=__declspec(dllexport):")
+  endif()
+else()
+  set(FLIGHT_PROTOC_VISIBILITY
+      "dllexport_decl=__attribute__((visibility(\\\"default\\\"))):")
+endif()
+
 add_custom_command(OUTPUT ${FLIGHT_GENERATED_PROTO_FILES}
                    DEPENDS ${PROTO_DEPENDS} ARGS
                    COMMAND ${FLIGHT_PROTOC_COMMAND}
-                           "--cpp_out=${CMAKE_CURRENT_BINARY_DIR}" "${FLIGHT_PROTO}"
+                           "--cpp_out=${FLIGHT_PROTOC_VISIBILITY}${CMAKE_CURRENT_BINARY_DIR}"
+                           "${FLIGHT_PROTO}"
                    COMMAND ${FLIGHT_PROTOC_COMMAND}
                            "--grpc_out=${CMAKE_CURRENT_BINARY_DIR}"
                            "--plugin=protoc-gen-grpc=$<TARGET_FILE:gRPC::grpc_cpp_plugin>"

cpp/src/arrow/flight/flight_internals_test.cc

@@ -702,7 +702,6 @@ TEST_F(TestCookieParsing, CookieCache) {
 // Protobuf tests
 
 TEST(GrpcTransport, FlightDataDeserialize) {
-#ifndef _WIN32
   pb::FlightData raw;
   // Tack on known and unknown fields by hand here
   raw.GetReflection()->MutableUnknownFields(&raw)->AddFixed32(900, 1024);
@@ -725,9 +724,6 @@ TEST(GrpcTransport, FlightDataDeserialize) {
   ASSERT_EQ("data", out.body->ToString());
 
   grpc_slice_unref(slice);
-#else
-  GTEST_SKIP() << "Can't use Protobuf symbols on Windows";
-#endif
 }
 
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