[CodeGen Protobuf support] protoc-gen-grpc-swift v2 (#1778)

Motivation:

We want to have a protoc plugin for grpc-swift v2 which builds on top of the code generator pipeline.

Modifications:

- Created the ProtobufCodeGenerator struct that encapsulates all setps needed to generate code for a given file descriptor
- Created tests for the ProtobufCodeGenerator
- added a new option for selecting v2 for the plugin
- modified main() accordingly

Result:

The protoc plugin for grpc-swift will support v2 and will use the CodeGen library.

Author: stefanadranca

Package.swift

@@ -236,7 +236,8 @@ extension Target {
     dependencies: [
       .protobuf,
       .protobufPluginLibrary,
-      .grpcCodeGen
+      .grpcCodeGen,
+      .grpcProtobufCodeGen
     ],
     exclude: [
       "README.md",

Sources/GRPCCodeGen/SourceGenerator.swift

@@ -35,6 +35,13 @@ public struct SourceGenerator: Sendable {
     /// Whether or not server code should be generated.
     public var server: Bool
 
+    public init(accessLevel: AccessLevel, client: Bool, server: Bool, indentation: Int = 4) {
+      self.accessLevel = accessLevel
+      self.indentation = indentation
+      self.client = client
+      self.server = server
+    }
+
     /// The possible access levels for the generated code.
     public struct AccessLevel: Sendable, Hashable {
       internal var level: Level

Sources/GRPCProtobufCodeGen/ProtobufCodeGenerator.swift

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2024, gRPC Authors All rights reserved.
+ *
+ * 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.
+ */
+
+import GRPCCodeGen
+import SwiftProtobufPluginLibrary
+
+public struct ProtobufCodeGenerator {
+  internal var configuration: SourceGenerator.Configuration
+
+  public init(configuration: SourceGenerator.Configuration) {
+    self.configuration = configuration
+  }
+
+  public func generateCode(from fileDescriptor: FileDescriptor) throws -> String {
+    let parser = ProtobufCodeGenParser()
+    let sourceGenerator = SourceGenerator(configuration: self.configuration)
+
+    let codeGenerationRequest = try parser.parse(input: fileDescriptor)
+    let sourceFile = try sourceGenerator.generate(codeGenerationRequest)
+    return sourceFile.contents
+  }
+}

Sources/protoc-gen-grpc-swift/main.swift

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 import Foundation
+import GRPCCodeGen
+import GRPCProtobufCodeGen
 import SwiftProtobuf
 import SwiftProtobufPluginLibrary
 
@@ -166,9 +168,16 @@ func main(args: [String]) throws {
           fileNamingOption: options.fileNaming,
           generatedFiles: &generatedFiles
         )
-        let grpcGenerator = Generator(fileDescriptor, options: options)
+        if options.v2 {
+          let grpcGenerator = ProtobufCodeGenerator(
+            configuration: SourceGenerator.Configuration(options: options)
+          )
+          grpcFile.content = try grpcGenerator.generateCode(from: fileDescriptor)
+        } else {
+          let grpcGenerator = Generator(fileDescriptor, options: options)
+          grpcFile.content = grpcGenerator.code
+        }
         grpcFile.name = grpcFileName
-        grpcFile.content = grpcGenerator.code
         response.file.append(grpcFile)
       }
     }
@@ -184,3 +193,22 @@ do {
 } catch {
   Log("ERROR: \(error)")
 }
+
+extension SourceGenerator.Configuration {
+  init(options: GeneratorOptions) {
+    let accessLevel: SourceGenerator.Configuration.AccessLevel
+    switch options.visibility {
+    case .internal:
+      accessLevel = .internal
+    case .package:
+      accessLevel = .package
+    case .public:
+      accessLevel = .public
+    }
+    self.init(
+      accessLevel: accessLevel,
+      client: options.generateClient,
+      server: options.generateServer
+    )
+  }
+}

Sources/protoc-gen-grpc-swift/options.swift

@@ -68,6 +68,7 @@ final class GeneratorOptions {
   private(set) var gRPCModuleName = "GRPC"
   private(set) var swiftProtobufModuleName = "SwiftProtobuf"
   private(set) var generateReflectionData = false
+  private(set) var v2 = false
 
   init(parameter: String?) throws {
     for pair in GeneratorOptions.parseParameter(string: parameter) {
@@ -154,6 +155,13 @@ final class GeneratorOptions {
           throw GenerationError.invalidParameterValue(name: pair.key, value: pair.value)
         }
 
+      case "_V2":
+        if let value = Bool(pair.value) {
+          self.v2 = value
+        } else {
+          throw GenerationError.invalidParameterValue(name: pair.key, value: pair.value)
+        }
+
       default:
         throw GenerationError.unknownParameter(name: pair.key)
       }

Tests/GRPCProtobufCodeGenTests/ProtobufCodeGenParserTests.swift

@@ -23,8 +23,16 @@ import XCTest
 
 final class ProtobufCodeGenParserTests: XCTestCase {
   func testParser() throws {
+    let descriptorSet = DescriptorSet(protos: [Google_Protobuf_FileDescriptorProto.helloWorld])
+    guard let fileDescriptor = descriptorSet.fileDescriptor(named: "helloworld.proto") else {
+      return XCTFail(
+        """
+        Could not find the file descriptor of "helloworld.proto".
+        """
+      )
+    }
     let parsedCodeGenRequest = try ProtobufCodeGenParser().parse(
-      input: self.helloWorldFileDescriptor
+      input: fileDescriptor
     )
     XCTAssertEqual(parsedCodeGenRequest.fileName, "helloworld.proto")
     XCTAssertEqual(
@@ -105,8 +113,10 @@ final class ProtobufCodeGenParserTests: XCTestCase {
       CodeGenerationRequest.Dependency(module: "GRPCProtobuf")
     )
   }
+}
 
-  var helloWorldFileDescriptor: FileDescriptor {
+extension Google_Protobuf_FileDescriptorProto {
+  static var helloWorld: Google_Protobuf_FileDescriptorProto {
     let requestType = Google_Protobuf_DescriptorProto.with {
       $0.name = "HelloRequest"
       $0.field = [
@@ -144,7 +154,7 @@ final class ProtobufCodeGenParserTests: XCTestCase {
         }
       ]
     }
-    let protoDescriptor = Google_Protobuf_FileDescriptorProto.with {
+    return Google_Protobuf_FileDescriptorProto.with {
       $0.name = "helloworld.proto"
       $0.package = "helloworld"
       $0.messageType = [requestType, responseType]
@@ -187,7 +197,5 @@ final class ProtobufCodeGenParserTests: XCTestCase {
       }
       $0.syntax = "proto3"
     }
-    let descriptorSet = DescriptorSet(protos: [protoDescriptor])
-    return descriptorSet.fileDescriptor(named: "helloworld.proto")!
   }
 }