Simplify and update code gen tests

Motivation:

The protobuf code generator doesn't actually do a lot: it parses a
protobuf file descriptor and turns that into a request for the code
generator provided by the GRPCCodeGen module. This means that the tests
should focus on the conversion rather than the generated code (although
this is still useful to test at a high level).

As it stands all tests are done on the generated code rather than the
conversion to a code generator request. The existing tests also hand
roll a protobuf file descriptor which is tedious and error prone.

The upstream code generator also has changes which aren't yet reflected
here.

Modifications:

- Define some test proto files for which we generate serialized
  protobuf file descriptor sets.
- Add a suite of code gen parser tests which check the request created
  from the file descriptor proto.
- Add a single code generator test.
- Downgrade an access level from public to package as public wasn't
  necessary.

Result:

Better tests

Author: glbrntt

Package.swift

@@ -94,6 +94,9 @@ let targets: [Target] = [
       .product(name: "SwiftProtobuf", package: "swift-protobuf"),
       .product(name: "SwiftProtobufPluginLibrary", package: "swift-protobuf"),
     ],
+    resources: [
+      .copy("Generated")
+    ],
     swiftSettings: defaultSwiftSettings
   ),
 ]

Sources/GRPCProtobufCodeGen/ProtobufCodeGenParser.swift

@@ -15,45 +15,50 @@
  */
 
 internal import Foundation
-internal import GRPCCodeGen
-internal import SwiftProtobufPluginLibrary
+internal import SwiftProtobuf
+package import SwiftProtobufPluginLibrary
+
+package import struct GRPCCodeGen.CodeGenerationRequest
+package import struct GRPCCodeGen.Dependency
+package import struct GRPCCodeGen.MethodDescriptor
+package import struct GRPCCodeGen.Name
+package import struct GRPCCodeGen.ServiceDescriptor
+package import struct GRPCCodeGen.SourceGenerator
 
 /// Parses a ``FileDescriptor`` object into a ``CodeGenerationRequest`` object.
-internal struct ProtobufCodeGenParser {
-  let input: FileDescriptor
-  let namer: SwiftProtobufNamer
+package struct ProtobufCodeGenParser {
   let extraModuleImports: [String]
   let protoToModuleMappings: ProtoFileToModuleMappings
   let accessLevel: SourceGenerator.Config.AccessLevel
 
-  internal init(
-    input: FileDescriptor,
+  package init(
     protoFileModuleMappings: ProtoFileToModuleMappings,
     extraModuleImports: [String],
     accessLevel: SourceGenerator.Config.AccessLevel
   ) {
-    self.input = input
     self.extraModuleImports = extraModuleImports
     self.protoToModuleMappings = protoFileModuleMappings
-    self.namer = SwiftProtobufNamer(
-      currentFile: input,
-      protoFileToModuleMappings: protoFileModuleMappings
-    )
     self.accessLevel = accessLevel
   }
 
-  internal func parse() throws -> CodeGenerationRequest {
-    var header = self.input.header
+  package func parse(descriptor: FileDescriptor) throws -> CodeGenerationRequest {
+    let namer = SwiftProtobufNamer(
+      currentFile: descriptor,
+      protoFileToModuleMappings: self.protoToModuleMappings
+    )
+
+    var header = descriptor.header
     // Ensuring there is a blank line after the header.
     if !header.isEmpty && !header.hasSuffix("\n\n") {
       header.append("\n")
     }
+
     let leadingTrivia = """
       // DO NOT EDIT.
       // swift-format-ignore-file
       //
       // Generated by the gRPC Swift generator plugin for the protocol buffer compiler.
-      // Source: \(self.input.name)
+      // Source: \(descriptor.name)
       //
       // For information on using the generated types, please see the documentation:
       //   https://github.com/grpc/grpc-swift
@@ -65,19 +70,20 @@ internal struct ProtobufCodeGenParser {
     let lookupDeserializer: (String) -> String = { messageType in
       "GRPCProtobuf.ProtobufDeserializer<\(messageType)>()"
     }
-    let services = self.input.services.map {
-      ServiceDescriptor(
+
+    let services = descriptor.services.map {
+      GRPCCodeGen.ServiceDescriptor(
         descriptor: $0,
-        package: input.package,
-        protobufNamer: self.namer,
-        file: self.input
+        package: descriptor.package,
+        protobufNamer: namer,
+        file: descriptor
       )
     }
 
     return CodeGenerationRequest(
-      fileName: self.input.name,
+      fileName: descriptor.name,
       leadingTrivia: header + leadingTrivia,
-      dependencies: self.codeDependencies,
+      dependencies: self.codeDependencies(file: descriptor),
       services: services,
       lookupSerializer: lookupSerializer,
       lookupDeserializer: lookupDeserializer
@@ -86,14 +92,16 @@ internal struct ProtobufCodeGenParser {
 }
 
 extension ProtobufCodeGenParser {
-  fileprivate var codeDependencies: [Dependency] {
+  fileprivate func codeDependencies(
+    file: FileDescriptor
+  ) -> [Dependency] {
     var codeDependencies: [Dependency] = [
       .init(module: "GRPCProtobuf", accessLevel: .internal)
     ]
     // Adding as dependencies the modules containing generated code or types for
     // '.proto' files imported in the '.proto' file we are parsing.
     codeDependencies.append(
-      contentsOf: (self.protoToModuleMappings.neededModules(forFile: self.input) ?? []).map {
+      contentsOf: (self.protoToModuleMappings.neededModules(forFile: file) ?? []).map {
         Dependency(module: $0, accessLevel: self.accessLevel)
       }
     )

Sources/GRPCProtobufCodeGen/ProtobufCodeGenerator.swift

@@ -14,32 +14,31 @@
  * limitations under the License.
  */
 
-public import GRPCCodeGen
-public import SwiftProtobufPluginLibrary
+package import GRPCCodeGen
+package import SwiftProtobufPluginLibrary
 
-public struct ProtobufCodeGenerator {
-  internal var configuration: SourceGenerator.Config
+package struct ProtobufCodeGenerator {
+  internal var config: SourceGenerator.Config
 
-  public init(
-    configuration: SourceGenerator.Config
+  package init(
+    config: SourceGenerator.Config
   ) {
-    self.configuration = configuration
+    self.config = config
   }
 
-  public func generateCode(
-    from fileDescriptor: FileDescriptor,
+  package func generateCode(
+    fileDescriptor: FileDescriptor,
     protoFileModuleMappings: ProtoFileToModuleMappings,
     extraModuleImports: [String]
   ) throws -> String {
     let parser = ProtobufCodeGenParser(
-      input: fileDescriptor,
       protoFileModuleMappings: protoFileModuleMappings,
       extraModuleImports: extraModuleImports,
-      accessLevel: self.configuration.accessLevel
+      accessLevel: self.config.accessLevel
     )
-    let sourceGenerator = SourceGenerator(config: self.configuration)
+    let sourceGenerator = SourceGenerator(config: self.config)
 
-    let codeGenerationRequest = try parser.parse()
+    let codeGenerationRequest = try parser.parse(descriptor: fileDescriptor)
     let sourceFile = try sourceGenerator.generate(codeGenerationRequest)
     return sourceFile.contents
   }

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

@@ -96,9 +96,9 @@ final class GenerateGRPC: CodeGenerator {
     )
 
     let config = SourceGenerator.Config(options: options)
-    let fileGenerator = ProtobufCodeGenerator(configuration: config)
+    let fileGenerator = ProtobufCodeGenerator(config: config)
     let contents = try fileGenerator.generateCode(
-      from: descriptor,
+      fileDescriptor: descriptor,
       protoFileModuleMappings: options.protoToModuleMappings,
       extraModuleImports: options.extraModuleImports
     )