Add comments to the generated header file

5 files changed, 116 insertions, 3 deletions

diff --git a/src/compiler/config.h b/src/compiler/config.h
index fea976c318..a826dd9744 100644
--- a/src/compiler/config.h
+++ b/src/compiler/config.h
@@ -44,6 +44,7 @@
 #define GRPC_CUSTOM_FILEDESCRIPTOR ::google::protobuf::FileDescriptor
 #define GRPC_CUSTOM_METHODDESCRIPTOR ::google::protobuf::MethodDescriptor
 #define GRPC_CUSTOM_SERVICEDESCRIPTOR ::google::protobuf::ServiceDescriptor
+#define GRPC_CUSTOM_SOURCELOCATION ::google::protobuf::SourceLocation
 #endif
 
 #ifndef GRPC_CUSTOM_CODEGENERATOR
@@ -74,6 +75,7 @@ typedef GRPC_CUSTOM_DESCRIPTOR Descriptor;
 typedef GRPC_CUSTOM_FILEDESCRIPTOR FileDescriptor;
 typedef GRPC_CUSTOM_METHODDESCRIPTOR MethodDescriptor;
 typedef GRPC_CUSTOM_SERVICEDESCRIPTOR ServiceDescriptor;
+typedef GRPC_CUSTOM_SOURCELOCATION SourceLocation;
 namespace compiler {
 typedef GRPC_CUSTOM_CODEGENERATOR CodeGenerator;
 typedef GRPC_CUSTOM_GENERATORCONTEXT GeneratorContext;
diff --git a/src/compiler/cpp_generator.cc b/src/compiler/cpp_generator.cc
index b133699306..97455cdbfd 100644
--- a/src/compiler/cpp_generator.cc
+++ b/src/compiler/cpp_generator.cc
@@ -101,6 +101,7 @@ grpc::string GetHeaderPrologue(File *file, const Parameters &params) {
     printer->Print(vars,
                   "// If you make any local change, they will be lost.\n");
     printer->Print(vars, "// source: $filename$\n");
+    printer->Print(file->GetLeadingComments().c_str());
     printer->Print(vars, "#ifndef GRPC_$filename_identifier$__INCLUDED\n");
     printer->Print(vars, "#define GRPC_$filename_identifier$__INCLUDED\n");
     printer->Print(vars, "\n");
@@ -455,6 +456,7 @@ void PrintHeaderServerMethodSync(Printer *printer, const Method *method,
   (*vars)["Method"] = method->name();
   (*vars)["Request"] = method->input_type_name();
   (*vars)["Response"] = method->output_type_name();
+  printer->Print(method->GetLeadingComments().c_str());
   if (method->NoStreaming()) {
     printer->Print(*vars,
                    "virtual ::grpc::Status $Method$("
@@ -479,6 +481,7 @@ void PrintHeaderServerMethodSync(Printer *printer, const Method *method,
         "::grpc::ServerReaderWriter< $Response$, $Request$>* stream);"
         "\n");
   }
+  printer->Print(method->GetTrailingComments().c_str());
 }
 
 void PrintHeaderServerMethodAsync(
@@ -673,6 +676,7 @@ void PrintHeaderService(Printer *printer,
                         std::map<grpc::string, grpc::string> *vars) {
   (*vars)["Service"] = service->name();
 
+  printer->Print(service->GetLeadingComments().c_str());
   printer->Print(*vars,
                  "class $Service$ GRPC_FINAL {\n"
                  " public:\n");
@@ -685,7 +689,9 @@ void PrintHeaderService(Printer *printer,
   printer->Indent();
   printer->Print("virtual ~StubInterface() {}\n");
   for (int i = 0; i < service->method_count(); ++i) {
+    printer->Print(service->method(i)->GetLeadingComments().c_str());
     PrintHeaderClientMethodInterfaces(printer, service->method(i).get(), vars, true);
+    printer->Print(service->method(i)->GetTrailingComments().c_str());
   }
   printer->Outdent();
   printer->Print("private:\n");
@@ -761,6 +767,7 @@ void PrintHeaderService(Printer *printer,
 
   printer->Outdent();
   printer->Print("};\n");
+  printer->Print(service->GetTrailingComments().c_str());
 }
 
 grpc::string GetHeaderServices(File *file,
@@ -817,6 +824,8 @@ grpc::string GetHeaderEpilogue(File *file,
 
     printer->Print(vars, "\n");
     printer->Print(vars, "#endif  // GRPC_$filename_identifier$__INCLUDED\n");
+
+    printer->Print(file->GetTrailingComments().c_str());
   }
   return output;
 }
@@ -836,6 +845,7 @@ grpc::string GetSourcePrologue(File *file,
     printer->Print(vars,
                   "// If you make any local change, they will be lost.\n");
     printer->Print(vars, "// source: $filename$\n\n");
+
     printer->Print(vars, "#include \"$filename_base$.pb.h\"\n");
     printer->Print(vars, "#include \"$filename_base$.grpc.pb.h\"\n");
     printer->Print(vars, "\n");
diff --git a/src/compiler/cpp_generator.h b/src/compiler/cpp_generator.h
index 99a60a2eae..1e68dfe3df 100644
--- a/src/compiler/cpp_generator.h
+++ b/src/compiler/cpp_generator.h
@@ -64,8 +64,15 @@ struct Parameters {
   grpc::string grpc_search_path;
 };
 
+// A common interface for objects having comments in the source.
+struct CommentHolder {
+  virtual ~CommentHolder() {}
+  virtual grpc::string GetLeadingComments() const = 0;
+  virtual grpc::string GetTrailingComments() const = 0;
+};
+
 // An abstract interface representing a method.
-struct Method {
+struct Method : public CommentHolder {
   virtual ~Method() {}
 
   virtual grpc::string name() const = 0;
@@ -80,7 +87,7 @@ struct Method {
 };
 
 // An abstract interface representing a service.
-struct Service {
+struct Service : public CommentHolder {
   virtual ~Service() {}
 
   virtual grpc::string name() const = 0;
@@ -101,7 +108,7 @@ struct Printer {
 
 // An interface that allows the source generated to be output using various
 // libraries/idls/serializers.
-struct File {
+struct File : public CommentHolder {
   virtual ~File() {}
 
   virtual grpc::string filename() const = 0;
diff --git a/src/compiler/cpp_plugin.cc b/src/compiler/cpp_plugin.cc
index f703c6453d..6128b816a4 100644
--- a/src/compiler/cpp_plugin.cc
+++ b/src/compiler/cpp_plugin.cc
@@ -35,11 +35,46 @@
 //
 
 #include <memory>
+#include <sstream>
 
 #include "src/compiler/config.h"
 
 #include "src/compiler/cpp_generator.h"
 #include "src/compiler/cpp_generator_helpers.h"
+#include "src/compiler/generator_helpers.h"
+
+grpc::string GenerateComments(const std::vector<grpc::string> &in) {
+  std::ostringstream oss;
+  for (const grpc::string &elem : in) {
+    if (elem.empty()) {
+      oss << "//\n";
+    } else if (elem[0] == ' ') {
+      oss << "//" << elem << "\n";
+    } else {
+      oss << "// " << elem << "\n";
+    }
+  }
+  return oss.str();
+}
+
+// Get leading or trailing comments in a string. Comment lines start with "// ".
+// Leading detached comments are put in in front of leading comments.
+template <typename DescriptorType>
+grpc::string GetComments(const DescriptorType *desc, bool leading) {
+  std::vector<grpc::string> out;
+  if (leading) {
+    grpc_generator::GetComment(
+        desc, grpc_generator::COMMENTTYPE_LEADING_DETACHED, &out);
+    std::vector<grpc::string> leading;
+    grpc_generator::GetComment(desc, grpc_generator::COMMENTTYPE_LEADING,
+                               &leading);
+    out.insert(out.end(), leading.begin(), leading.end());
+  } else {
+    grpc_generator::GetComment(desc, grpc_generator::COMMENTTYPE_TRAILING,
+                               &out);
+  }
+  return GenerateComments(out);
+}
 
 class ProtoBufMethod : public grpc_cpp_generator::Method {
  public:
@@ -71,6 +106,12 @@ class ProtoBufMethod : public grpc_cpp_generator::Method {
     return method_->client_streaming() && method_->server_streaming();
   }
 
+  grpc::string GetLeadingComments() const { return GetComments(method_, true); }
+
+  grpc::string GetTrailingComments() const {
+    return GetComments(method_, false);
+  }
+
  private:
   const grpc::protobuf::MethodDescriptor *method_;
 };
@@ -88,6 +129,14 @@ class ProtoBufService : public grpc_cpp_generator::Service {
           new ProtoBufMethod(service_->method(i)));
   };
 
+  grpc::string GetLeadingComments() const {
+    return GetComments(service_, true);
+  }
+
+  grpc::string GetTrailingComments() const {
+    return GetComments(service_, false);
+  }
+
  private:
   const grpc::protobuf::ServiceDescriptor *service_;
 };
@@ -136,6 +185,10 @@ class ProtoBufFile : public grpc_cpp_generator::File {
           new ProtoBufPrinter(str));
   }
 
+  grpc::string GetLeadingComments() const { return GetComments(file_, true); }
+
+  grpc::string GetTrailingComments() const { return GetComments(file_, false); }
+
  private:
   const grpc::protobuf::FileDescriptor *file_;
 };
diff --git a/src/compiler/generator_helpers.h b/src/compiler/generator_helpers.h
index e1bb66a875..7cfea9d96d 100644
--- a/src/compiler/generator_helpers.h
+++ b/src/compiler/generator_helpers.h
@@ -35,6 +35,9 @@
 #define GRPC_INTERNAL_COMPILER_GENERATOR_HELPERS_H
 
 #include <map>
+#include <sstream>
+#include <string>
+#include <vector>
 
 #include "src/compiler/config.h"
 
@@ -165,6 +168,44 @@ inline MethodType GetMethodType(const grpc::protobuf::MethodDescriptor *method)
   }
 }
 
+inline void Split(const grpc::string &s, char delim,
+                  std::vector<grpc::string> *append_to) {
+  std::istringstream iss(s);
+  grpc::string piece;
+  while (std::getline(iss, piece)) {
+    append_to->push_back(piece);
+  }
+}
+
+enum CommentType {
+  COMMENTTYPE_LEADING,
+  COMMENTTYPE_TRAILING,
+  COMMENTTYPE_LEADING_DETACHED
+};
+
+// Get all the comments and append each line to out.
+template <typename DescriptorType>
+inline void GetComment(const DescriptorType *desc, CommentType type,
+                       std::vector<grpc::string> *out) {
+  grpc::protobuf::SourceLocation location;
+  if (!desc->GetSourceLocation(&location)) {
+    return;
+  }
+  if (type == COMMENTTYPE_LEADING || type == COMMENTTYPE_TRAILING) {
+    const grpc::string &comments = type == COMMENTTYPE_LEADING
+                                       ? location.leading_comments
+                                       : location.trailing_comments;
+    Split(comments, '\n', out);
+  } else if (type == COMMENTTYPE_LEADING_DETACHED) {
+    for (int i = 0; i < location.leading_detached_comments.size(); i++) {
+      Split(location.leading_detached_comments[i], '\n', out);
+      out->push_back("");
+    }
+  } else {
+    abort();
+  }
+}
+
 }  // namespace grpc_generator
 
 #endif  // GRPC_INTERNAL_COMPILER_GENERATOR_HELPERS_H