FindProtobuf: add flag to allow descriptor files to be generated

- The .desc files will be in the same folder as the generated .cc and .h files.
- Paths to generate .desc files are stored in a variable passed in
- This is only implemented for C++
- Remove legacy ARGS
- Add test that generates and uses C++ protobuf message
- Add test that checks that the generated .desc file can be instantiated
  with DynamicMessageFactory
- Add Help rst for new feature

5 files changed, 98 insertions, 1 deletions

diff --git a/Tests/FindProtobuf/Test/CMakeLists.txt b/Tests/FindProtobuf/Test/CMakeLists.txt
index 10ce976..bc89190 100644
--- a/Tests/FindProtobuf/Test/CMakeLists.txt
+++ b/Tests/FindProtobuf/Test/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.8)
 project(TestFindProtobuf CXX)
 include(CTest)
 
@@ -32,3 +32,19 @@ target_link_libraries(test_var_protoc PRIVATE ${Protobuf_PROTOC_LIBRARIES})
 add_test(NAME test_var_protoc COMMAND test_var_protoc)
 
 add_test(NAME test_tgt_protoc_version COMMAND protobuf::protoc --version)
+
+set(Protobuf_IMPORT_DIRS ${Protobuf_INCLUDE_DIRS})
+PROTOBUF_GENERATE_CPP(PROTO_SRC PROTO_HEADER msgs/example.proto)
+PROTOBUF_GENERATE_CPP(DESC_PROTO_SRC DESC_PROTO_HEADER DESCRIPTORS DESC_PROTO_DESC msgs/example_desc.proto)
+add_library(msgs ${PROTO_SRC} ${PROTO_HEADER})
+
+add_executable(test_generate main-generate.cxx ${PROTO_SRC})
+target_include_directories(test_generate PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
+target_link_libraries(test_generate msgs ${Protobuf_LIBRARIES})
+add_test(NAME test_generate COMMAND test_generate)
+
+add_executable(test_desc main-desc.cxx ${DESC_PROTO_SRC})
+target_compile_features(test_desc PRIVATE cxx_std_11)
+target_include_directories(test_desc PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
+target_link_libraries(test_desc msgs ${Protobuf_LIBRARIES})
+add_test(NAME test_desc COMMAND test_desc ${DESC_PROTO_DESC})
diff --git a/Tests/FindProtobuf/Test/main-desc.cxx b/Tests/FindProtobuf/Test/main-desc.cxx
new file mode 100644
index 0000000..a26e562
--- /dev/null
+++ b/Tests/FindProtobuf/Test/main-desc.cxx
@@ -0,0 +1,57 @@
+#include <fstream>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/descriptor.pb.h>
+#include <google/protobuf/dynamic_message.h>
+#include <google/protobuf/text_format.h>
+#include <iostream>
+#include <string>
+
+int main(int argc, char* argv[])
+{
+  std::ifstream fs;
+  fs.open(argv[1], std::ifstream::in);
+  google::protobuf::FileDescriptorSet file_descriptor_set;
+  file_descriptor_set.ParseFromIstream(&fs);
+
+  const google::protobuf::DescriptorPool* compiled_pool =
+    google::protobuf::DescriptorPool::generated_pool();
+
+  if (compiled_pool == NULL) {
+    std::cerr << "compiled pool is NULL." << std::endl;
+    return 1;
+  }
+
+  google::protobuf::DescriptorPool pool(compiled_pool);
+  google::protobuf::DynamicMessageFactory dynamic_message_factory(&pool);
+
+  for (const google::protobuf::FileDescriptorProto& file_descriptor_proto :
+       file_descriptor_set.file()) {
+    const google::protobuf::FileDescriptor* file_descriptor =
+      pool.BuildFile(file_descriptor_proto);
+    if (file_descriptor == NULL) {
+      continue;
+    }
+
+    const google::protobuf::Descriptor* descriptor =
+      pool.FindMessageTypeByName("example.msgs.ExampleDesc");
+
+    if (descriptor == NULL) {
+      continue;
+    }
+
+    google::protobuf::Message* msg =
+      dynamic_message_factory.GetPrototype(descriptor)->New();
+    std::string data = "data: 1";
+    bool success = google::protobuf::TextFormat::ParseFromString(data, msg);
+
+    if (success) {
+      return 0;
+    } else {
+      std::cerr << "Failed to parse message." << std::endl;
+      return 2;
+    }
+  }
+
+  std::cerr << "No matching message found." << std::endl;
+  return 3;
+}
diff --git a/Tests/FindProtobuf/Test/main-generate.cxx b/Tests/FindProtobuf/Test/main-generate.cxx
new file mode 100644
index 0000000..ca33a68
--- /dev/null
+++ b/Tests/FindProtobuf/Test/main-generate.cxx
@@ -0,0 +1,8 @@
+#include <example.pb.h>
+
+int main()
+{
+  example::msgs::Example msg;
+
+  return 0;
+}
diff --git a/Tests/FindProtobuf/Test/msgs/example.proto b/Tests/FindProtobuf/Test/msgs/example.proto
new file mode 100644
index 0000000..d27262e
--- /dev/null
+++ b/Tests/FindProtobuf/Test/msgs/example.proto
@@ -0,0 +1,6 @@
+syntax = "proto2";
+package example.msgs;
+
+message Example {
+  required int32 data = 1;
+}
diff --git a/Tests/FindProtobuf/Test/msgs/example_desc.proto b/Tests/FindProtobuf/Test/msgs/example_desc.proto
new file mode 100644
index 0000000..4454473
--- /dev/null
+++ b/Tests/FindProtobuf/Test/msgs/example_desc.proto
@@ -0,0 +1,10 @@
+syntax = "proto2";
+package example.msgs;
+
+import "google/protobuf/descriptor.proto";
+
+message ExampleDesc {
+  required int32 data = 1;
+
+  optional google.protobuf.FileDescriptorSet desc = 2;
+}