Introduce generate option to customize output

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## [Unreleased]
 
+- Add `generate=<service|client|both>` option to customize generated output - [#23](https://github.com/collectiveidea/protoc-gen-twirp_ruby/pull/23)
 - Add `skip-empty` option to prevent generating empty scaffolding for proto files without services - [#21](https://github.com/collectiveidea/protoc-gen-twirp_ruby/pull/21) 
 - Refactor code generator to improve internal readability - [#12](https://github.com/collectiveidea/protoc-gen-twirp_ruby/pull/12), [#13](https://github.com/collectiveidea/protoc-gen-twirp_ruby/pull/13), [#22](https://github.com/collectiveidea/protoc-gen-twirp_ruby/pull/22)
 - Remove unnecessary extra files from packaged gem - [#11](https://github.com/collectiveidea/protoc-gen-twirp_ruby/pull/11)

README.md

@@ -55,7 +55,7 @@ that might affect migration include:
 
  * Generated output code is in [standardrb style](https://github.com/standardrb/standard).
  * Generated service and client class names are improved for well-named protobuf services. See [#6](https://github.com/collectiveidea/protoc-gen-twirp_ruby/pull/6).
- * Supports options: `skip-empty`
+ * Supports various protoc command line [configuration options](https://github.com/collectiveidea/protoc-gen-twirp_ruby?tab=readme-ov-file#options).
 
 ## Usage
 
@@ -70,7 +70,13 @@ protoc --proto_path=. --ruby_out=. --twirp_ruby_out=. ./path/to/service.proto
 The plugin supports the following options to configure code generation. Pass options by
 specifying `--twirp_ruby_opt=<option>` on the `protoc` command line.
 
- * `skip-empty`: Avoid generating a `_twirp.rb` for a `.proto` with no service definitions. 
+ * `skip-empty`: Avoid generating a `_twirp.rb` for a `.proto` with no service definitions. By default, a `_twirp.rb`
+   file is generated for every proto file listed on the command line, even if the file is empty scaffolding. 
+ * `generate=<service|client|both>`: Customize generated output to include generated services, clients, or both.
+   * `generate=service` - only generate `::Twirp::Service` subclass(es).
+   * `generate=client` - only generate `::Twirp::Client` subclass(es).
+   * `generate=both` - generate both services and clients. This is the default option to preserve
+     backwards compatibility.
 
 ## Development
 

lib/twirp/protoc_plugin/code_generator.rb

@@ -11,9 +11,10 @@ module ProtocPlugin
     class CodeGenerator
       # @param proto_file [Google::Protobuf::FileDescriptorProto]
       # @param relative_ruby_protobuf [String] e.g. "example_rb.pb"
-      # @param options [Hash{Symbol => Boolean}]
+      # @param options [Hash{Symbol => Boolean, Symbol}]
       #   * :skip_empty [Boolean] indicating whether generation should skip creating a twirp file
-      #       for proto files that contain no services. Default false.
+      #       for proto files that contain no services.
+      #   * :generate [Symbol] one of: :service, :client, or :both.
       def initialize(proto_file, relative_ruby_protobuf, options)
         @proto_file = proto_file
         @relative_ruby_protobuf = relative_ruby_protobuf
@@ -49,33 +50,22 @@ def generate
         end
 
         @proto_file.service.each_with_index do |service, index| # service: <Google::Protobuf::ServiceDescriptorProto>
-          # Add newline between service definitions when multiple are generated
+          # Add newline between definitions when multiple are generated
           output << "\n" if index > 0
 
-          service_name = service.name
-          service_class_name = service.service_class_name
-
-          # Generate service class
-          output << line("class #{service_class_name} < ::Twirp::Service", indent_level)
-          output << line("  package \"#{@proto_file.package}\"", indent_level) unless @proto_file.package.to_s.empty?
-          output << line("  service \"#{service_name}\"", indent_level)
-          service["method"].each do |method| # method: <Google::Protobuf::MethodDescriptorProto>
-            input_type = convert_to_ruby_type(method.input_type, current_module)
-            output_type = convert_to_ruby_type(method.output_type, current_module)
-            ruby_method_name = method.name.snake_case
-
-            output << line("  rpc :#{method.name}, #{input_type}, #{output_type}, ruby_method: :#{ruby_method_name}", indent_level)
+          if %i[service both].include?(@options[:generate])
+            generate_service_class(output, indent_level, service, @proto_file.package, current_module)
           end
-          output << line("end", indent_level)
 
-          # Generate client class
+          if @options[:generate] == :both
+            # Space between generated service and client when generating both
+            output << "\n"
 
-          client_class_name = service.client_class_name
-
-          output << "\n"
-          output << line("class #{client_class_name} < ::Twirp::Client", indent_level)
-          output << line("  client_for #{service_class_name}", indent_level)
-          output << line("end", indent_level)
+            generate_client_class_for_service(output, indent_level, service)
+          elsif @options[:generate] == :client
+            # When generating only the client, we can't use the `client_for` DSL.
+            generate_client_class_standalone(output, indent_level, service, @proto_file.package, current_module)
+          end
         end
 
         modules.each do |_|
@@ -98,6 +88,73 @@ def line(input, indent_level = 0)
         "#{"  " * indent_level}#{input}\n"
       end
 
+      # Generates a Twirp::Service subclass for the given service class, adding the
+      # string to the output.
+      #
+      # @param output [#<<] the output to append the generated service code to
+      # @param indent_level [Integer] the number of double spaces to indent the generated code by
+      # @param service [Google::Protobuf::ServiceDescriptorProto]
+      # @param package [String, nil] the optional package of the proto file that contains the service, e.g. "example.hello_world"
+      # @param current_module [String, nil] the optional name of the containing module, e.g. "::Example::HelloWorld"
+      # @return [void]
+      def generate_service_class(output, indent_level, service, package, current_module)
+        service_name = service.name
+        service_class_name = service.service_class_name
+
+        # Generate service class
+        output << line("class #{service_class_name} < ::Twirp::Service", indent_level)
+        output << line("  package \"#{package}\"", indent_level) unless package.to_s.empty?
+        output << line("  service \"#{service_name}\"", indent_level)
+        service["method"].each do |method| # method: <Google::Protobuf::MethodDescriptorProto>
+          input_type = convert_to_ruby_type(method.input_type, current_module)
+          output_type = convert_to_ruby_type(method.output_type, current_module)
+          ruby_method_name = method.name.snake_case
+
+          output << line("  rpc :#{method.name}, #{input_type}, #{output_type}, ruby_method: :#{ruby_method_name}", indent_level)
+        end
+        output << line("end", indent_level)
+      end
+
+      # Generates a Twirp::Client subclass for the given service class, adding the
+      # string to the output.
+      #
+      # @param output [#<<] the output to append the generated service code to
+      # @param indent_level [Integer] the number of double spaces to indent the generated code by
+      # @param service [Google::Protobuf::ServiceDescriptorProto]
+      # @return [void]
+      def generate_client_class_for_service(output, indent_level, service)
+        output << line("class #{service.client_class_name} < ::Twirp::Client", indent_level)
+        output << line("  client_for #{service.service_class_name}", indent_level)
+        output << line("end", indent_level)
+      end
+
+      # Generates a Twirp::Client subclass standalone, without using the `client_for` DSL because
+      # there is no corresponding service to reference.
+      #
+      # This essentially in-lines the `client_for` logic from
+      # https://github.com/arthurnn/twirp-ruby/blob/v1.11.0/lib/twirp/client.rb#L31
+      #
+      # @param output [#<<] the output to append the generated service code to
+      # @param indent_level [Integer] the number of double spaces to indent the generated code by
+      # @param service [Google::Protobuf::ServiceDescriptorProto]
+      # @param package [String, nil] the optional package of the proto file that contains the service, e.g. "example.hello_world"
+      # @param current_module [String, nil] the optional name of the containing module, e.g. "::Example::HelloWorld"
+      # @return [void]
+      def generate_client_class_standalone(output, indent_level, service, package, current_module)
+        output << line("class #{service.client_class_name} < ::Twirp::Client", indent_level)
+        output << line("  package \"#{package}\"", indent_level) unless package.to_s.empty?
+        output << line("  service \"#{service.name}\"", indent_level)
+        service["method"].each do |method| # method: <Google::Protobuf::MethodDescriptorProto>
+          input_type = convert_to_ruby_type(method.input_type, current_module)
+          output_type = convert_to_ruby_type(method.output_type, current_module)
+          ruby_method_name = method.name.snake_case
+
+          # TRICKY: The service `rpc` DSL accepts a method symbol, but the client `rpc` DSL expects a string.
+          output << line("  rpc \"#{method.name}\", #{input_type}, #{output_type}, ruby_method: :#{ruby_method_name}", indent_level)
+        end
+        output << line("end", indent_level)
+      end
+
       # Converts either a package string like ".some.example.api" or a namespaced
       # message like "google.protobuf.Empty" to an Array of Strings that can be
       # used as Ruby constants (when joined with "::").

lib/twirp/protoc_plugin/process.rb

@@ -42,14 +42,16 @@ def process(input)
       #   array format, e.g. "some-flag,key1=value1".
       #
       #   The only valid parameter is currently the optional "skip-empty" flag.
-      # @return [Hash{Symbol => Boolean}]
+      # @return [Hash{Symbol => Boolean, Symbol}]
       #   * :skip_empty [Boolean] indicating whether generation should skip creating a twirp file
       #       for proto files that contain no services. Default false.
+      #   * :generate [Symbol] one of: :service, :client, or :both. Default :both.
       # @raise [ArgumentError] when a required parameter is missing, a parameter value is invalid, or
       #   an unrecognized parameter is present on the command line
       def extract_options(params)
         opts = {
-          skip_empty: false
+          skip_empty: false,
+          generate: :both
         }
 
         # Process the options passed to the plugin from `protoc`.
@@ -62,6 +64,17 @@ def extract_options(params)
               raise ArgumentError, "Unexpected value passed to skip-empty flag: #{value}"
             end
             opts[:skip_empty] = true
+          elsif key == "generate"
+            if value.nil? || value.empty?
+              raise ArgumentError, "Unexpected missing value for generate option. Please supply one of: service, client, both."
+            end
+
+            value_as_symbol = value&.to_sym
+            unless %i[service client both].include?(value_as_symbol)
+              raise ArgumentError, "The generate value must be one of: service, client, both. Unexpectedly received: #{value}"
+            end
+
+            opts[:generate] = value_as_symbol
           else
             raise ArgumentError, "Invalid option: #{key}"
           end

spec/fixtures/complex_example/api.proto

@@ -0,0 +1,49 @@
+syntax = "proto3";
+
+// This is a contrived example that demonstrates:
+//
+// 1. Code generation for multiple services, each with multiple rpcs
+// 2. Using imported types for request and response types
+// 3. Services proto in a completely different package
+//
+// This file does _not_ demonstrate best practices.
+
+package api;
+
+import "common/rpc/status.proto";
+import "common/type/color.proto";
+import "common/type/time_of_day.proto";
+
+service GreetService {
+  rpc SayHello(HelloRequest) returns (HelloResponse);
+  rpc SayGoodbye(GoodbyeRequest) returns (GoodbyeResponse);
+  rpc ChangeColor(.common.type.Color) returns (ChangeColorResponse);
+}
+
+service StatusService {
+  rpc GetStatus(StatusRequest) returns (.common.rpc.Status);
+  rpc GetTimeOfDay(TimeOfDayRequest) returns (common.type.TimeOfDay);
+}
+
+message HelloRequest {
+  string name = 1;
+}
+
+message HelloResponse {
+  string response = 1;
+  .common.type.Color favorite_color = 2;
+}
+
+message GoodbyeRequest {
+  string name = 1;
+}
+
+message GoodbyeResponse {
+  string response = 1;
+}
+
+message ChangeColorResponse {}
+
+message StatusRequest {}
+
+message TimeOfDayRequest {}

spec/fixtures/complex_example/common/rpc/status.proto

@@ -0,0 +1,11 @@
+syntax = "proto3";
+
+package common.rpc;
+
+import "google/protobuf/any.proto";
+
+message Status {
+  int32 code = 1;
+  string message = 2;
+  repeated google.protobuf.Any details = 3;
+}

spec/fixtures/complex_example/common/type/color.proto

@@ -0,0 +1,10 @@
+syntax = "proto3";
+
+package common.type;
+
+message Color {
+  float red = 1;
+  float green = 2;
+  float blue = 3;
+  float alpha = 4;
+}

spec/fixtures/complex_example/common/type/time_of_day.proto

@@ -0,0 +1,13 @@
+syntax = "proto3";
+
+package common.type;
+
+message TimeOfDay {
+  enum Meridiem {
+    UNKNOWN = 0;
+    ANTE = 1;
+    POST = 2;
+  }
+
+  Meridiem am_or_pm = 1;
+}

spec/twirp/protoc_plugin/code_generator_spec.rb

@@ -5,7 +5,7 @@
   # the `process_spec.rb`. But, in order to get to the private helper methods
   # to test, we have to stand up an instance that we can send messages to.
   let(:proto_file_descriptor) { Google::Protobuf::FileDescriptorProto.new }
-  let(:options) { {skip_empty: false} }
+  let(:options) { {skip_empty: false, generate: :both} }
   let(:code_generator) { Twirp::ProtocPlugin::CodeGenerator.new(proto_file_descriptor, "example_rb.pb", options) }
 
   describe "#split_to_constants" do