[gRPC] Add new options to control the gRPC code generation. (#8298)

The new options are:

-  `--grpc-filename-suffix` controls the suffix of the generated files;
-  `--grpc-use-system-headers` controls the type of C++ includes generated;
-  `--grpc-search-path` controls the directory that contains gRPC runtime;
-  `--grpc-additional-header` allows to provide additional dependencies for the generated code.

grpc/src/compiler/cpp_generator.cc

@@ -8,8 +8,6 @@
 namespace grpc_cpp_generator {
 namespace {
 
-static grpc::string service_header_ext() { return ".grpc.fb.h"; }
-
 template<class T>
 static grpc::string as_string(T x) {
   std::ostringstream out;
@@ -1137,7 +1135,7 @@ grpc::string GetSourcePrologue(grpc_generator::File *file,
     vars["filename"] = file->filename();
     vars["filename_base"] = file->filename_without_ext();
     vars["message_header_ext"] = params.message_header_extension;
-    vars["service_header_ext"] = service_header_ext();
+    vars["service_header_ext"] = params.service_header_extension;
 
     printer->Print(vars, "// Generated by the gRPC C++ plugin.\n");
     printer->Print(vars,
@@ -1557,7 +1555,7 @@ grpc::string GetMockPrologue(grpc_generator::File *file,
     vars["filename"] = file->filename();
     vars["filename_base"] = file->filename_without_ext();
     vars["message_header_ext"] = params.message_header_extension;
-    vars["service_header_ext"] = service_header_ext();
+    vars["service_header_ext"] = params.service_header_extension;
 
     printer->Print(vars, "// Generated by the gRPC C++ plugin.\n");
     printer->Print(vars,

grpc/src/compiler/cpp_generator.h

@@ -35,6 +35,8 @@ struct Parameters {
   bool generate_mock_code;
   // By default, use "_generated.h"
   std::string message_header_extension;
+  // Default: ".grpc.fb.h"
+  std::string service_header_extension;
 };
 
 // Return the prologue of the generated header file.

include/flatbuffers/idl.h

@@ -22,6 +22,7 @@
 #include <map>
 #include <memory>
 #include <stack>
+#include <vector>
 
 #include "flatbuffers/base.h"
 #include "flatbuffers/flatbuffers.h"
@@ -759,6 +760,12 @@ struct IDLOptions {
   // make the flatbuffer more compact.
   bool set_empty_vectors_to_null;
 
+  /*********************************** gRPC ***********************************/
+  std::string grpc_filename_suffix;
+  bool grpc_use_system_headers;
+  std::string grpc_search_path;
+  std::vector<std::string> grpc_additional_headers;
+
   IDLOptions()
       : gen_jvmstatic(false),
         use_flexbuffers(false),
@@ -829,7 +836,9 @@ struct IDLOptions {
         rust_module_root_file(false),
         lang_to_generate(0),
         set_empty_strings_to_null(true),
-        set_empty_vectors_to_null(true) {}
+        set_empty_vectors_to_null(true),
+        grpc_filename_suffix(".fb"),
+        grpc_use_system_headers(true) {}
 };
 
 // This encapsulates where the parser is in the current source file.

src/flatc.cpp

@@ -258,6 +258,13 @@ const static FlatCOption flatc_options[] = {
     "Omit emission of namespace entrypoint file" },
   { "", "file-names-only", "",
     "Print out generated file names without writing to the files" },
+  { "", "grpc-filename-suffix", "SUFFIX",
+    "The suffix for the generated file names (Default is '.fb')." },
+  { "", "grpc-additional-header", "",
+    "Additional headers to prepend to the generated files." },
+  { "", "grpc-use-system-headers", "",
+    "Use <> for headers included from the generated code." },
+  { "", "grpc-search-path", "PATH", "Prefix to any gRPC includes." },
 };
 
 auto cmp = [](FlatCOption a, FlatCOption b) { return a.long_opt < b.long_opt; };
@@ -674,6 +681,30 @@ FlatCOptions FlatCompiler::ParseFromCommandLineArguments(int argc,
       } else if (arg == "--file-names-only") {
         // TODO (khhn): Provide 2 implementation
         options.file_names_only = true;
+      } else if (arg == "--grpc-filename-suffix") {
+        if (++argi >= argc) Error("missing gRPC filename suffix: " + arg, true);
+        opts.grpc_filename_suffix = argv[argi];
+      } else if (arg.rfind("--grpc-filename-suffix=", 0) == 0) {
+        opts.grpc_filename_suffix =
+            arg.substr(std::string("--grpc-filename-suffix=").size());
+      } else if (arg == "--grpc-additional-header") {
+        if (++argi >= argc) Error("missing include following: " + arg, true);
+        opts.grpc_additional_headers.push_back(argv[argi]);
+      } else if (arg.rfind("--grpc-additional-header=", 0) == 0) {
+        opts.grpc_additional_headers.push_back(
+            arg.substr(std::string("--grpc-additional-header=").size()));
+      } else if (arg == "--grpc-search-path") {
+        if (++argi >= argc) Error("missing gRPC search path: " + arg, true);
+        opts.grpc_search_path = argv[argi];
+      } else if (arg.rfind("--grpc-search-path=", 0) == 0) {
+        opts.grpc_search_path =
+            arg.substr(std::string("--grpc-search-path=").size());
+      } else if (arg == "--grpc-use-system-headers" ||
+                 arg == "--grpc-use-system-headers=true") {
+        opts.grpc_use_system_headers = true;
+      } else if (arg == "--no-grpc-use-system-headers" ||
+                 arg == "--grpc-use-system-headers=false") {
+        opts.grpc_use_system_headers = false;
       } else {
         if (arg == "--proto") { opts.proto_mode = true; }
 

src/idl_gen_grpc.cpp

@@ -16,6 +16,8 @@
 
 // independent from idl_parser, since this code is not needed for most clients
 
+#include <cstdio>
+
 #include "flatbuffers/code_generators.h"
 #include "flatbuffers/flatbuffers.h"
 #include "flatbuffers/idl.h"
@@ -253,6 +255,15 @@ class FlatBufFile : public grpc_generator::File {
   std::string additional_headers() const {
     switch (language_) {
       case kLanguageCpp: {
+        if (!parser_.opts.grpc_additional_headers.empty()) {
+          std::string result = "";
+          for (const std::string &header :
+               parser_.opts.grpc_additional_headers) {
+            if (!result.empty()) result += "\n";
+            result += "#include \"" + header + "\"";
+          }
+          return result;
+        }
         return "#include \"flatbuffers/grpc.h\"\n";
       }
       case kLanguageGo: {
@@ -356,10 +367,16 @@ bool GenerateCppGRPC(const Parser &parser, const std::string &path,
 
   grpc_cpp_generator::Parameters generator_parameters;
   // TODO(wvo): make the other parameters in this struct configurable.
-  generator_parameters.use_system_headers = true;
+  generator_parameters.use_system_headers = opts.grpc_use_system_headers;
   generator_parameters.message_header_extension = suffix;
-
-  FlatBufFile fbfile(parser, file_name, FlatBufFile::kLanguageCpp);
+  generator_parameters.service_header_extension =
+      ".grpc" + opts.grpc_filename_suffix + ".h";
+  generator_parameters.grpc_search_path = opts.grpc_search_path;
+  std::string filename = flatbuffers::StripExtension(parser.file_being_parsed_);
+  if (!opts.keep_prefix) {
+    filename = flatbuffers::StripPath(filename);
+  }
+  FlatBufFile fbfile(parser, filename, FlatBufFile::kLanguageCpp);
 
   std::string header_code =
       grpc_cpp_generator::GetHeaderPrologue(&fbfile, generator_parameters) +
@@ -373,10 +390,14 @@ bool GenerateCppGRPC(const Parser &parser, const std::string &path,
       grpc_cpp_generator::GetSourceServices(&fbfile, generator_parameters) +
       grpc_cpp_generator::GetSourceEpilogue(&fbfile, generator_parameters);
 
-  return flatbuffers::SaveFile((path + file_name + ".grpc.fb.h").c_str(),
-                               header_code, false) &&
-         flatbuffers::SaveFile((path + file_name + ".grpc.fb.cc").c_str(),
-                               source_code, false);
+  return flatbuffers::SaveFile(
+             (path + file_name + ".grpc" + opts.grpc_filename_suffix + ".h")
+                 .c_str(),
+             header_code, false) &&
+         flatbuffers::SaveFile(
+             (path + file_name + ".grpc" + opts.grpc_filename_suffix + ".cc")
+                 .c_str(),
+             source_code, false);
 }
 
 class JavaGRPCGenerator : public flatbuffers::BaseGenerator {