[CSHARP] Add base_namespace experimental option to C# plugin

src/compiler/csharp_generator_helpers.h

@@ -22,13 +22,30 @@
 #include "src/compiler/config.h"
 #include "src/compiler/generator_helpers.h"
 
+using google::protobuf::compiler::csharp::GetOutputFile;
+
 namespace grpc_csharp_generator {
 
 inline bool ServicesFilename(const grpc::protobuf::FileDescriptor* file,
                              const std::string& file_suffix,
-                             std::string& out_file_name_or_error) {
-  out_file_name_or_error =
-      grpc_generator::FileNameInUpperCamel(file, false) + file_suffix;
+                             const std::string& base_namespace,
+                             std::string& out_file, std::string* error) {
+  // Support for base_namespace option is **experimental**.
+  //
+  // If base_namespace is provided then slightly different name mangling
+  // is used to generate the service file name. This is because this
+  // uses common code with protoc. For most file names this will not
+  // make a difference (only files with punctuation or numbers in the
+  // name.)
+  // Otherwise the behavor remains the same as before.
+  if (base_namespace.empty()) {
+    out_file = grpc_generator::FileNameInUpperCamel(file, false) + file_suffix;
+  } else {
+    out_file = GetOutputFile(file, file_suffix, true, base_namespace, error);
+    if (out_file.empty()) {
+      return false;
+    }
+  }
   return true;
 }
 

src/compiler/csharp_plugin.cc

@@ -43,6 +43,8 @@ class CSharpGrpcGenerator : public grpc::protobuf::compiler::CodeGenerator {
     bool generate_client = true;
     bool generate_server = true;
     bool internal_access = false;
+    std::string base_namespace = "";
+
     // the suffix that will get appended to the name generated from the name
     // of the original .proto file
     std::string file_suffix = "Grpc.cs";
@@ -55,6 +57,11 @@ class CSharpGrpcGenerator : public grpc::protobuf::compiler::CodeGenerator {
         internal_access = true;
       } else if (options[i].first == "file_suffix") {
         file_suffix = options[i].second;
+      } else if (options[i].first == "base_namespace") {
+        // Support for base_namespace option in this plugin is experimental.
+        // The option may be removed or file names generated may change
+        // in the future.
+        base_namespace = options[i].second;
       } else {
         *error = "Unknown generator option: " + options[i].first;
         return false;
@@ -69,8 +76,8 @@ class CSharpGrpcGenerator : public grpc::protobuf::compiler::CodeGenerator {
 
     // Get output file name.
     std::string file_name;
-    if (!grpc_csharp_generator::ServicesFilename(file, file_suffix,
-                                                 file_name)) {
+    if (!grpc_csharp_generator::ServicesFilename(
+            file, file_suffix, base_namespace, file_name, error)) {
       return false;
     }
     std::unique_ptr<grpc::protobuf::io::ZeroCopyOutputStream> output(

src/csharp/BUILD-INTEGRATION.md

@@ -170,12 +170,21 @@ to perform code generation. Here is an overview of the available `grpc_csharp_pl
 | no_client       | off       | Don't generate the client stub                           |
 | no_server       | off       | Don't generate the server-side stub                      |
 | internal_access | off       | Generate classes with "internal" visibility              |
+| file_suffix     | Grpc.cs   | The suffix that will get appended to the name of the generated file. **Can only be used on the command line.** |
+| base_namespace | none       | *Experimental - may change or be removed.* Same as `base_namespace` for `protoc` C# options.  **Can only be used on the command line.** |
 
-Note that the protocol buffer compiler has a special commandline syntax for plugin options.
-Example:
-```
-protoc --plugin=protoc-gen-grpc=grpc_csharp_plugin --csharp_out=OUT_DIR \
-    --grpc_out=OUT_DIR --grpc_opt=lite_client,no_server \
+To use these options with `Grpc.Tools` specify them in the __GrpcOutputOptions__
+metadata in the `<Protobuf>` item.
+- Note: `file_suffix` and `base_namespace` should not be used with `Grpc.Tools`. Using them will break the build.
+
+To use these options on the command line specify them using the `--grpc_opt`
+command line option, e.g.:
+
+```bash
+protoc --plugin=protoc-gen-grpc=grpc_csharp_plugin \
+    --csharp_out=OUT_DIR \
+    --grpc_out=OUT_DIR \
+    --grpc_opt=no_server,base_namespace=Example \
     -I INCLUDE_DIR foo.proto
 ```
 ## Environment Variables