feat: add HTTP transcoding support and update tests

Signed-off-by: Yordis Prieto <yordis.prieto@gmail.com>

Author: yordis

cmd/protoc-gen-elixir-grpc/README.md

@@ -35,6 +35,66 @@ plugins:
 
 Server modules are generated into the same directory structure as the protobuf definitions, with `.server.pb.ex` suffix.
 
+### Configuration Options
+
+You can configure the plugin using parameters:
+
+#### HTTP Transcoding
+
+Enable HTTP/JSON transcoding support for your gRPC services:
+
+```yaml
+version: v2
+plugins:
+  - local: protoc-gen-elixir
+    out: lib
+  - local: protoc-gen-elixir-grpc
+    out: lib
+    opt:
+      - http_transcode=true
+```
+
+This generates:
+
+```elixir
+defmodule Greeter.Server do
+  use GRPC.Server, service: Greeter.Service, http_transcode: true
+  
+  # ... method delegates
+end
+```
+
+#### Custom Handler Module Prefix
+
+Organize handlers under a custom module prefix instead of using the protobuf package:
+
+```yaml
+version: v2
+plugins:
+  - local: protoc-gen-elixir
+    out: lib
+  - local: protoc-gen-elixir-grpc
+    out: lib
+    opt:
+      - handler_module_prefix=MyApp.Handlers
+```
+
+#### Combining Options
+
+You can combine multiple options:
+
+```yaml
+version: v2
+plugins:
+  - local: protoc-gen-elixir
+    out: lib
+  - local: protoc-gen-elixir-grpc
+    out: lib
+    opt:
+      - http_transcode=true
+      - handler_module_prefix=MyApp.Handlers
+```
+
 ### Basic Service Implementation
 
 For more realistic applications that require dependencies like database connections, implement handlers 

cmd/protoc-gen-elixir-grpc/main.go

@@ -53,8 +53,9 @@ const (
 	defaultPackagePrefix    = ""
 	packagePrefixFlag       = "package_prefix"
 	handlerModulePrefixFlag = "handler_module_prefix"
+	httpTranscodeFlag       = "http_transcode"
 
-	usage = "\n\nFlags:\n  -h, --help\tPrint this help and exit.\n      --version\tPrint the version and exit.\n      --handler_module_prefix\tCustom Elixir module prefix for handler modules instead of protobuf package."
+	usage = "\n\nFlags:\n  -h, --help\tPrint this help and exit.\n      --version\tPrint the version and exit.\n      --handler_module_prefix\tCustom Elixir module prefix for handler modules instead of protobuf package.\n      --http_transcode\tEnable HTTP transcoding support (adds http_transcode: true to use GRPC.Server)."
 )
 
 func parsePluginParameters(paramStr string, flagSet *flag.FlagSet) error {
@@ -111,6 +112,11 @@ func main() {
 		"",
 		"Custom Elixir module prefix for handler modules instead of protobuf package (e.g., 'MyApp.Handlers').",
 	)
+	httpTranscode := flagSet.Bool(
+		httpTranscodeFlag,
+		false,
+		"Enable HTTP transcoding support (adds http_transcode: true to use GRPC.Server).",
+	)
 
 	input, err := io.ReadAll(os.Stdin)
 	if err != nil {
@@ -162,7 +168,7 @@ func main() {
 			continue
 		}
 
-		generateElixirFile(resp, protoFile, *packagePrefix, *handlerModulePrefix)
+		generateElixirFile(resp, protoFile, *packagePrefix, *handlerModulePrefix, *httpTranscode)
 	}
 
 	output, err := proto.Marshal(resp)
@@ -177,7 +183,7 @@ func main() {
 	}
 }
 
-func generateElixirFile(resp *pluginpb.CodeGeneratorResponse, file *descriptorpb.FileDescriptorProto, packagePrefix, handlerModulePrefix string) {
+func generateElixirFile(resp *pluginpb.CodeGeneratorResponse, file *descriptorpb.FileDescriptorProto, packagePrefix, handlerModulePrefix string, httpTranscode bool) {
 	if len(file.Service) == 0 {
 		return
 	}
@@ -191,7 +197,7 @@ func generateElixirFile(resp *pluginpb.CodeGeneratorResponse, file *descriptorpb
 	content.WriteString("\n")
 
 	for _, service := range file.Service {
-		generateServiceModule(&content, file, service, handlerModulePrefix)
+		generateServiceModule(&content, file, service, handlerModulePrefix, httpTranscode)
 		content.WriteString("\n")
 	}
 
@@ -201,13 +207,16 @@ func generateElixirFile(resp *pluginpb.CodeGeneratorResponse, file *descriptorpb
 	})
 }
 
-func generateServiceModule(content *strings.Builder, file *descriptorpb.FileDescriptorProto, service *descriptorpb.ServiceDescriptorProto, handlerModulePrefix string) {
+func generateServiceModule(content *strings.Builder, file *descriptorpb.FileDescriptorProto, service *descriptorpb.ServiceDescriptorProto, handlerModulePrefix string, httpTranscode bool) {
 	serverModuleName := generateServerModuleName(file, service)
 	serviceModuleName := generateServiceModuleName(file, service)
 
 	content.WriteString("defmodule " + serverModuleName + " do\n")
-	content.WriteString("  use GRPC.Server, service: " + serviceModuleName + "\n")
-	content.WriteString("\n")
+	content.WriteString("  use GRPC.Server, service: " + serviceModuleName)
+	if httpTranscode {
+		content.WriteString(", http_transcode: true")
+	}
+	content.WriteString("\n\n")
 
 	for _, method := range service.Method {
 		generateMethodDelegate(content, file, service, method, handlerModulePrefix)

cmd/protoc-gen-elixir-grpc/main_test.go

@@ -151,15 +151,15 @@ end
 				Parameter:             ptr("handler_module_prefix=MyApp.Handlers"),
 			}
 
-		rsp := testGenerate(t, req)
-		assert.Nil(t, rsp.Error)
-		assert.Equal(t, 1, len(rsp.File))
+			rsp := testGenerate(t, req)
+			assert.Nil(t, rsp.Error)
+			assert.Equal(t, 1, len(rsp.File))
 
-		file := rsp.File[0]
-		assert.Equal(t, "auth/v1/auth.server.pb.ex", file.GetName())
+			file := rsp.File[0]
+			assert.Equal(t, "auth/v1/auth.server.pb.ex", file.GetName())
 
-		content := file.GetContent()
-		expected := `# Code generated by protoc-gen-elixir-grpc. DO NOT EDIT.
+			content := file.GetContent()
+			expected := `# Code generated by protoc-gen-elixir-grpc. DO NOT EDIT.
 #
 # Source: auth/v1/auth.proto
 
@@ -169,7 +169,58 @@ defmodule Auth.V1.AuthService.Server do
   defdelegate login(request, stream), to: MyApp.Handlers.Auth.V1.AuthService.Server.LoginHandler, as: :handle_message
 end
 `
-		assert.Equal(t, expected, content)
+			assert.Equal(t, expected, content)
+		})
+
+		t.Run("with http_transcode option", func(t *testing.T) {
+			fileDesc := &descriptorpb.FileDescriptorProto{
+				Name:    ptr("api/v1/api.proto"),
+				Package: ptr("api.v1"),
+				MessageType: []*descriptorpb.DescriptorProto{
+					{Name: ptr("GetRequest")},
+					{Name: ptr("GetResponse")},
+				},
+				Service: []*descriptorpb.ServiceDescriptorProto{
+					{
+						Name: ptr("ApiService"),
+						Method: []*descriptorpb.MethodDescriptorProto{
+							{
+								Name:       ptr("Get"),
+								InputType:  ptr(".api.v1.GetRequest"),
+								OutputType: ptr(".api.v1.GetResponse"),
+							},
+						},
+					},
+				},
+			}
+
+			req := &pluginpb.CodeGeneratorRequest{
+				FileToGenerate:        []string{"api/v1/api.proto"},
+				ProtoFile:             []*descriptorpb.FileDescriptorProto{fileDesc},
+				SourceFileDescriptors: []*descriptorpb.FileDescriptorProto{fileDesc},
+				CompilerVersion:       compilerVersion,
+				Parameter:             ptr("http_transcode=true"),
+			}
+
+			rsp := testGenerate(t, req)
+			assert.Nil(t, rsp.Error)
+			assert.Equal(t, 1, len(rsp.File))
+
+			file := rsp.File[0]
+			assert.Equal(t, "api/v1/api.server.pb.ex", file.GetName())
+
+			content := file.GetContent()
+			expected := `# Code generated by protoc-gen-elixir-grpc. DO NOT EDIT.
+#
+# Source: api/v1/api.proto
+
+defmodule Api.V1.ApiService.Server do
+  use GRPC.Server, service: Api.V1.ApiService.Service, http_transcode: true
+
+  defdelegate get(request, stream), to: Api.V1.ApiService.Server.GetHandler, as: :handle_message
+end
+`
+			assert.Equal(t, expected, content)
 		})
 
 		t.Run("with package prefix", func(t *testing.T) {
@@ -202,15 +253,15 @@ end
 				Parameter:             ptr("package_prefix=lib/proto"),
 			}
 
-		rsp := testGenerate(t, req)
-		assert.Nil(t, rsp.Error)
-		assert.Equal(t, 1, len(rsp.File))
+			rsp := testGenerate(t, req)
+			assert.Nil(t, rsp.Error)
+			assert.Equal(t, 1, len(rsp.File))
 
-		file := rsp.File[0]
-		assert.Equal(t, "lib/proto/user/v1/user.server.pb.ex", file.GetName())
+			file := rsp.File[0]
+			assert.Equal(t, "lib/proto/user/v1/user.server.pb.ex", file.GetName())
 
-		content := file.GetContent()
-		expected := `# Code generated by protoc-gen-elixir-grpc. DO NOT EDIT.
+			content := file.GetContent()
+			expected := `# Code generated by protoc-gen-elixir-grpc. DO NOT EDIT.
 #
 # Source: user.proto
 
@@ -220,8 +271,8 @@ defmodule User.V1.UserService.Server do
   defdelegate get_user(request, stream), to: User.V1.UserService.Server.GetUserHandler, as: :handle_message
 end
 `
-		assert.Equal(t, expected, content)
-	})
+			assert.Equal(t, expected, content)
+		})
 
 		t.Run("with multiple parameters", func(t *testing.T) {
 			fileDesc := &descriptorpb.FileDescriptorProto{
@@ -270,6 +321,57 @@ defmodule Billing.V1.BillingService.Server do
 
   defdelegate create_invoice(request, stream), to: MyApp.BusinessLogic.Billing.V1.BillingService.Server.CreateInvoiceHandler, as: :handle_message
 end
+`
+			assert.Equal(t, expected, content)
+		})
+
+		t.Run("with http_transcode and handler_module_prefix", func(t *testing.T) {
+			fileDesc := &descriptorpb.FileDescriptorProto{
+				Name:    ptr("payment/v1/payment.proto"),
+				Package: ptr("payment.v1"),
+				MessageType: []*descriptorpb.DescriptorProto{
+					{Name: ptr("ProcessRequest")},
+					{Name: ptr("ProcessResponse")},
+				},
+				Service: []*descriptorpb.ServiceDescriptorProto{
+					{
+						Name: ptr("PaymentService"),
+						Method: []*descriptorpb.MethodDescriptorProto{
+							{
+								Name:       ptr("ProcessPayment"),
+								InputType:  ptr(".payment.v1.ProcessRequest"),
+								OutputType: ptr(".payment.v1.ProcessResponse"),
+							},
+						},
+					},
+				},
+			}
+
+			req := &pluginpb.CodeGeneratorRequest{
+				FileToGenerate:        []string{"payment/v1/payment.proto"},
+				ProtoFile:             []*descriptorpb.FileDescriptorProto{fileDesc},
+				SourceFileDescriptors: []*descriptorpb.FileDescriptorProto{fileDesc},
+				CompilerVersion:       compilerVersion,
+				Parameter:             ptr("http_transcode=true,handler_module_prefix=MyApp.Core"),
+			}
+
+			rsp := testGenerate(t, req)
+			assert.Nil(t, rsp.Error)
+			assert.Equal(t, 1, len(rsp.File))
+
+			file := rsp.File[0]
+			assert.Equal(t, "payment/v1/payment.server.pb.ex", file.GetName())
+
+			content := file.GetContent()
+			expected := `# Code generated by protoc-gen-elixir-grpc. DO NOT EDIT.
+#
+# Source: payment/v1/payment.proto
+
+defmodule Payment.V1.PaymentService.Server do
+  use GRPC.Server, service: Payment.V1.PaymentService.Service, http_transcode: true
+
+  defdelegate process_payment(request, stream), to: MyApp.Core.Payment.V1.PaymentService.Server.ProcessPaymentHandler, as: :handle_message
+end
 `
 			assert.Equal(t, expected, content)
 		})