Handle nested packages better

example/hello_world/service_twirp.rb

@@ -1,7 +1,8 @@
 # Code generated by protoc-gen-twirp_ruby, DO NOT EDIT.
 require 'twirp'
 
-module Example.helloWorld
+module Example
+  module HelloWorld
     class HelloWorldService < Twirp::Service
       package "example.hello_world"
       service "HelloWorld"
@@ -12,3 +13,4 @@ module Example.helloWorld
       client_for HelloWorldService
     end
   end
+end

protoc-gen-twirp_ruby/main.go

@@ -80,16 +80,28 @@ func (g *generator) Generate(in *plugin.CodeGeneratorRequest) *plugin.CodeGenera
 	return resp
 }
 
+// indentation represents the level of Ruby indentation for a block of code. It
+// implements the fmt.Stringer interface to output the correct number of spaces
+// for the given level of indentation
+type indentation int
+
+func (i indentation) String() string {
+	return strings.Repeat("  ", int(i))
+}
+
 func (g *generator) generateFile(file *descriptor.FileDescriptorProto) *plugin.CodeGeneratorResponse_File {
-	indent := ""
+	indent := indentation(0)
 	pkgName := pkgName(file)
 	g.P(`# Code generated by protoc-gen-twirp_ruby, DO NOT EDIT.`)
 	g.P(`require 'twirp'`)
 	g.P(``)
-	if pkgName != "" {
-		g.P(fmt.Sprintf("module %s", CamelCase(pkgName)))
-		indent = indent + "  "
+
+	modules := PackageToModules(pkgName)
+	for _, m := range modules {
+		g.P(fmt.Sprintf("%smodule %s", indent, m))
+		indent += 1
 	}
+
 	for i, service := range file.Service {
 		serviceName := serviceName(service)
 		g.P(fmt.Sprintf("%sclass %sService < Twirp::Service", indent, CamelCase(serviceName)))
@@ -113,8 +125,9 @@ func (g *generator) generateFile(file *descriptor.FileDescriptorProto) *plugin.C
 			g.P(``)
 		}
 	}
-	if pkgName != "" {
-		g.P(`end`)
+	for range modules {
+		indent -= 1
+		g.P(fmt.Sprintf("%send", indent))
 	}
 
 	resp := new(plugin.CodeGeneratorResponse_File)
@@ -217,6 +230,24 @@ func writeResponse(w io.Writer, resp *plugin.CodeGeneratorResponse) {
 	}
 }
 
+// Modules converts protobuf package name to a list of Ruby module names to
+// represent it.
+//
+// Example
+//
+//	PackageToModules("twitch.twirp.example.helloworld") => ["Twitch", "Twirp", "Example", "Helloworld]
+func PackageToModules(pkgName string) []string {
+	if pkgName == "" {
+		return nil
+	}
+
+	var parts []string
+	for _, p := range strings.Split(pkgName, ".") {
+		parts = append(parts, CamelCase(p))
+	}
+	return parts
+}
+
 // CamelCase converts a string from snake_case to CamelCased.
 //
 // If there is an interior underscore followed by a lower case letter, drop the

protoc-gen-twirp_ruby/main_test.go

@@ -0,0 +1,26 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestPackageToModules(t *testing.T) {
+	tests := []struct {
+		pkgName string
+		modules []string
+	}{
+		{"", nil},
+		{"example", []string{"Example"}},
+		{"twitch.twirp.example.helloworld", []string{"Twitch", "Twirp", "Example", "Helloworld"}},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.pkgName, func(t *testing.T) {
+			modules := PackageToModules(tt.pkgName)
+			if got, want := modules, tt.modules; !reflect.DeepEqual(got, want) {
+				t.Errorf("expected %v; got %v", want, got)
+			}
+		})
+	}
+}