Updates the ruby generator RubyAsType to correctly account for underscores in packages

Prior to this change, when the ruby generator tried to reference an entity that was not part of the same package
(or a direct parent package) and the package contains underscores,
the result would simply uppercase the first character.
It should however uppercase each letter that proceeds an underscore and remove underscores.

i.e.

```
package my_package.service;

import "my_package/data.proto";

service MyService {
  rpc Test (data.Request) returns data.Response {}
}
```

Was

```ruby
   # ...
   rpc :Test, My_package::Data::REquest, My_package::Data::Response
   # ...
```

Should be:

```ruby
   # ...
   rpc :Test, MyPackage::Data::REquest, My_package::Data::Response
   # ...
```

src/compiler/ruby_generator.cc

@@ -73,7 +73,7 @@ void PrintService(const ServiceDescriptor* service, const grpc::string& package,
   // Begin the service module
   std::map<grpc::string, grpc::string> module_vars = ListToDict({
       "module.name",
-      CapitalizeFirst(service->name()),
+      Modularize(service->name()),
   });
   out->Print(module_vars, "module $module.name$\n");
   out->Indent();

src/compiler/ruby_generator_string-inl.h

@@ -81,13 +81,23 @@ inline bool ReplacePrefix(grpc::string* s, const grpc::string& from,
   return true;
 }
 
-// CapitalizeFirst capitalizes the first char in a string.
-inline grpc::string CapitalizeFirst(grpc::string s) {
+// Modularize converts a string into a ruby module compatible name
+inline grpc::string Modularize(grpc::string s) {
   if (s.empty()) {
     return s;
   }
-  s[0] = ::toupper(s[0]);
-  return s;
+  grpc::string new_string = "";
+  bool was_last_underscore = false;
+  new_string.append(1, ::toupper(s[0]));
+  for (grpc::string::size_type i = 1; i < s.size(); ++i) {
+    if (was_last_underscore && s[i] != '_') {
+      new_string.append(1, ::toupper(s[i]));
+    } else if (s[i] != '_') {
+      new_string.append(1, s[i]);
+    }
+    was_last_underscore = s[i] == '_';
+  }
+  return new_string;
 }
 
 // RubyTypeOf updates a proto type to the required ruby equivalent.
@@ -106,7 +116,7 @@ inline grpc::string RubyTypeOf(const grpc::string& a_type,
         res += "::";  // switch '.' to the ruby module delim
       }
       if (i < prefixes_and_type.size() - 1) {
-        res += CapitalizeFirst(prefixes_and_type[i]);  // capitalize pkgs
+        res += Modularize(prefixes_and_type[i]);  // capitalize pkgs
       } else {
         res += prefixes_and_type[i];
       }

src/ruby/spec/pb/package_with_underscore/checker_spec.rb

@@ -0,0 +1,54 @@
+# Copyright 2016 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.
+
+require 'open3'
+require 'tmpdir'
+
+def debug_mode?
+  !ENV['CONFIG'].nil? && ENV['CONFIG'] == 'dbg'
+end
+
+describe 'Package with underscore protobuf code generation' do
+  it 'should have the same content as created by code generation' do
+    root_dir = File.join(File.dirname(__FILE__), '..', '..', '..', '..', '..')
+    pb_dir = File.join(root_dir, 'src', 'ruby', 'spec', 'pb')
+
+    bins_sub_dir = debug_mode? ? 'dbg' : 'opt'
+    bins_dir = File.join(root_dir, 'bins', bins_sub_dir)
+
+    plugin = File.join(bins_dir, 'grpc_ruby_plugin')
+    protoc = File.join(bins_dir, 'protobuf', 'protoc')
+
+    got = nil
+
+    Dir.mktmpdir do |tmp_dir|
+      gen_out = File.join(tmp_dir, 'package_with_underscore', 'service_services_pb.rb')
+
+      pid = spawn(
+        protoc,
+        '-I.',
+        'package_with_underscore/service.proto',
+        "--grpc_out=#{tmp_dir}",
+        "--plugin=protoc-gen-grpc=#{plugin}",
+        chdir: pb_dir)
+      Process.waitpid2(pid)
+      File.open(gen_out) { |f| got = f.read }
+    end
+
+    correct_modularized_rpc = 'rpc :TestOne, '                \
+      'Grpc::Testing::PackageWithUnderscore::Data::Request, ' \
+      'Grpc::Testing::PackageWithUnderscore::Data::Response'
+    expect(got).to include(correct_modularized_rpc)
+  end
+end

src/ruby/spec/pb/package_with_underscore/data.proto

@@ -0,0 +1,23 @@
+// Copyright 2018 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 grpc.testing.package_with_underscore.data;
+
+message Request {
+}
+
+message Response {
+}

src/ruby/spec/pb/package_with_underscore/service.proto

@@ -0,0 +1,23 @@
+// Copyright 2018 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 grpc.testing.package_with_underscore.service;
+
+import "package_with_underscore/data.proto";
+
+service MyService {
+  rpc TestOne(data.Request) returns (data.Response) {}
+}

tools/run_tests/helper_scripts/run_ruby.sh

@@ -18,4 +18,7 @@ set -ex
 # change to grpc repo root
 cd $(dirname $0)/../../..
 
+# build grpc_ruby_plugin
+make grpc_ruby_plugin -j8
+
 rake