[CSHARP] Add base_namespace experimental option to C# plugin (#32636)

Added `base_namespace` experimental option to `grpc_csharp_plugin` as
this has been requested several times by
people not using `Grpc.Tools` to generate their code - see
#28663

Notes:
- it should not be used with `Grpc.Tools`. That has a different way of
handling duplicate proto file names in different directories. Using this
option will break those builds. It can only be used on the `protoc`
command line.
- it uses common code with the `base_namespace` option for C# in
`protoc`, which unfortunately has a slightly different name mangling
algorithm for converting proto file names to C# camel case names. This
only affects files with punctation or numbers in the name. This should
not matter unless you are expecting specific file names
- See
https://protobuf.dev/reference/csharp/csharp-generated/#compiler_options
for an explanation of this option

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 behavior 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

@@ -173,12 +173,33 @@ 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](https://protobuf.dev/reference/csharp/csharp-generated/#compiler_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.
+
+Notes:
+- `file_suffix` and `base_namespace` should not be used with `Grpc.Tools`. Using them will break the build.
+
+- using `base_namespace` changes the algorithm for the generated file names to align it with the algorithm used by `protoc`.
+
+  This only affects files with punctuation or numbers in the name. E.g. `hello.world2d.proto` now generates file `HelloWorld2DGrpc.cs` instead of `Hello.world2dGrpc.cs`
+
+To use these options on the command line specify them with the `--grpc_opt`
+option.
+
+Code generated by `protoc` is independent of the plugin and you may also need to specify C# options for this with `--csharp_opt`.
+These are [documented here](https://protobuf.dev/reference/csharp/csharp-generated/#compiler_options).
+
+ e.g.:
+
+```bash
+protoc --plugin=protoc-gen-grpc=grpc_csharp_plugin \
+    --csharp_out=OUT_DIR \
+    --csharp_opt=base_namespace=Example \
+    --grpc_out=OUT_DIR \
+    --grpc_opt=no_server,base_namespace=Example \
     -I INCLUDE_DIR foo.proto
 ```
 ## Environment Variables

test/csharp/codegen/BUILD

@@ -56,3 +56,22 @@ grpc_sh_test(
     ],
     uses_polling = False,
 )
+
+grpc_sh_test(
+    name = "csharp_codegen_base_namespace_test",
+    size = "small",
+    srcs = ["csharp_codegen_base_namespace_test.sh"],
+    data = [
+        "basenamespace/proto/namespacetest.proto",
+        "//src/compiler:grpc_csharp_plugin",
+        "@com_google_protobuf//:protoc",
+    ],
+    tags = [
+        "no_windows",
+        "noasan",
+        "nomsan",
+        "notsan",
+        "noubsan",
+    ],
+    uses_polling = False,
+)

test/csharp/codegen/basenamespace/proto/namespacetest.proto

@@ -0,0 +1,37 @@
+// Copyright 2023 gRPC authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package test.csharp.codegen.basenamespace.test;
+
+option csharp_namespace = "Example.V1.CodegenTest";
+
+// The greeting service definition.
+service Greeter {
+  // Sends a greeting
+  rpc SayHello (HelloRequest) returns (HelloReply) {}
+
+  rpc SayHelloStreamReply (HelloRequest) returns (stream HelloReply) {}
+}
+
+// The request message containing the user's name.
+message HelloRequest {
+  string name = 1;
+}
+
+// The response message containing the greetings
+message HelloReply {
+  string message = 1;
+}

test/csharp/codegen/csharp_codegen_base_namespace_test.sh

@@ -0,0 +1,97 @@
+#!/bin/bash
+# Copyright 2023 gRPC authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Run this script via bazel test
+# It expects that protoc and grpc_csharp_plugin have already been built.
+
+# Simple test - compare generated output to expected files
+
+set -x
+
+TESTNAME=basenamespace
+
+# protoc and grpc_csharp_plugin binaries are supplied as "data" in bazel
+PROTOC=./external/com_google_protobuf/protoc
+PLUGIN=./src/compiler/grpc_csharp_plugin
+
+# where to find the test data
+DATA_DIR=./test/csharp/codegen/${TESTNAME}
+
+# output directory for the generated files
+PROTO_OUT=./proto_out
+rm -rf ${PROTO_OUT}
+mkdir -p ${PROTO_OUT}
+
+# run protoc and the plugin specifying the base_namespace options
+$PROTOC \
+    --plugin=protoc-gen-grpc-csharp=$PLUGIN \
+    --csharp_out=${PROTO_OUT} \
+    --grpc-csharp_out=${PROTO_OUT} \
+    --csharp_opt=base_namespace=Example \
+    --grpc-csharp_opt=base_namespace=Example \
+    -I ${DATA_DIR}/proto \
+    ${DATA_DIR}/proto/namespacetest.proto
+
+# log the files generated
+ls -lR ./proto_out
+
+# Verify the output files exist in the right location.
+# The base_namespace option does not change the generated code just
+# the location of the files. Contents are not checked in this test.
+
+# The C# namespace option in the proto file of "Example.V1.CodegenTest"
+# combined with the command line options above should mean the generated files
+# are created in the output directory "V1/CodegenTest"
+
+# First file is generated by protoc.
+[ -e ${PROTO_OUT}/V1/CodegenTest/Namespacetest.cs ] || {
+    echo >&2 "missing generated output, expecting V1/CodegenTest/Namespacetest.cs"
+    exit 1
+}
+
+# Second file is generated by the plugin.
+[ -e ${PROTO_OUT}/V1/CodegenTest/NamespacetestGrpc.cs ] || {
+    echo >&2 "missing generated output, expecting V1/CodegenTest/NamespacetestGrpc.cs"
+    exit 1
+}
+
+# Run again without the base_namespace options to check the files are created
+# in the root of the output directory
+
+rm -rf ${PROTO_OUT}
+mkdir -p ${PROTO_OUT}
+
+$PROTOC \
+    --plugin=protoc-gen-grpc-csharp=$PLUGIN \
+    --csharp_out=${PROTO_OUT} \
+    --grpc-csharp_out=${PROTO_OUT} \
+    -I ${DATA_DIR}/proto \
+    ${DATA_DIR}/proto/namespacetest.proto
+
+ls -lR ./proto_out
+
+[ -e ${PROTO_OUT}/Namespacetest.cs ] || {
+    echo >&2 "missing generated output, expecting Namespacetest.cs"
+    exit 1
+}
+
+[ -e ${PROTO_OUT}/NamespacetestGrpc.cs ] || {
+    echo >&2 "missing generated output, expecting NamespacetestGrpc.cs"
+    exit 1
+}
+
+# Run one extra command to clear $? before exiting the script to prevent
+# failing even when tests pass.
+echo "Plugin test: ${TESTNAME}: passed."