[CodeGenLib] Translator for enums containing type aliases and static properties (grpc#1733)

Motivation:

In the generated code we want to have:

- enums for each namespace containing enums for all their services
- enums for each service (inside the corresponding namespace enum) containing
enums for all their methods, an array of all corresponding MethodDescriptors and type aliases for streaming and non-streaming protocols
- enums for each method (inside the corresponding service enum) containing
type aliases for the input and output types and a method descriptor (GRPCCore)

Modifications:

- Created the Translator protocol defining the 'translate()' function.
- Implemented the IDLToStructuredSwiftTranslator struct which conforms to the Translator protocol and creates the StructuredSwiftRepresentation for a CodeGenerationRequest calling the Specialized translators' functions.
- Created the SpecializedTranslator protocol.
- Implemented the TypeAliasTranslator, the first of the 3 SpecializedTranslators that takes in a CodeGenerationRequest object and creates all the enums, type aliases and properties mentioned in the Motivation, in StructuredSwiftRepresentation format.
- Created CodeGenError.
- Wrote SnippetTests.

Result:

The generated code will contain useful type aliases for message types and
protocol names, organized in namespace, service and method specific enums.

Author: stefanadranca

NOTICES.txt

@@ -62,7 +62,7 @@ This product uses derivations of swift-extras/swift-extras-base64 'Base64.swift'
 
 This product uses derivations of apple/swift-openapi-generator 'StructuredSwiftRepresentation.swift',
 'TypeName.swift', 'TypeUsage.swift', 'Builtins.swift', 'RendererProtocol.swift', 'TextBasedProtocol',
-and 'Test_TextBasedRenderer'.
+'Test_TextBasedRenderer', and 'SnippetBasedReferenceTests.swift'.
 
     * LICENSE (Apache License 2.0):
       * https://github.com/apple/swift-openapi-generator/blob/main/LICENSE.txt

Sources/GRPCCodeGen/CodeGenError.swift

@@ -0,0 +1,64 @@
+/*
+ * Copyright 2023, 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.
+ */
+
+/// A error thrown by the ``SourceGenerator`` to signal errors in the ``CodeGenerationRequest`` object.
+public struct CodeGenError: Error, Hashable, Sendable {
+  /// The code indicating the domain of the error.
+  public var code: Code
+  /// A message providing more details about the error which may include details specific to this
+  /// instance of the error.
+  public var message: String
+
+  /// Creates a new error.
+  ///
+  /// - Parameters:
+  ///   - code: The error code.
+  ///   - message: A description of the error.
+  public init(code: Code, message: String) {
+    self.code = code
+    self.message = message
+  }
+}
+
+extension CodeGenError {
+  public struct Code: Hashable, Sendable {
+    private enum Value {
+      case nonUniqueServiceName
+      case nonUniqueMethodName
+    }
+
+    private var value: Value
+    private init(_ value: Value) {
+      self.value = value
+    }
+
+    /// The same name is used for two services that are either in the same namespace or don't have a namespace.
+    public static var nonUniqueServiceName: Self {
+      Self(.nonUniqueServiceName)
+    }
+
+    /// The same name is used for two methods of the same service.
+    public static var nonUniqueMethodName: Self {
+      Self(.nonUniqueMethodName)
+    }
+  }
+}
+
+extension CodeGenError: CustomStringConvertible {
+  public var description: String {
+    return "\(self.code): \"\(self.message)\""
+  }
+}

Sources/GRPCCodeGen/CodeGenerationRequest.swift

@@ -36,7 +36,7 @@ public struct CodeGenerationRequest {
   public var services: [ServiceDescriptor]
 
   /// Closure that receives a message type as a `String` and returns a code snippet to
-  /// initialize a `MessageSerializer` for that type as a `String`.
+  /// initialise a `MessageSerializer` for that type as a `String`.
   ///
   /// The result is inserted in the generated code, where clients serialize RPC inputs and
   /// servers serialize RPC outputs.
@@ -217,22 +217,22 @@ public struct CodeGenerationRequest {
       public var inputType: String
 
       /// The generated output type for the described method.
-      public var ouputType: String
+      public var outputType: String
 
       public init(
         documentation: String,
         name: String,
         isInputStreaming: Bool,
         isOutputStreaming: Bool,
         inputType: String,
-        ouputType: String
+        outputType: String
       ) {
         self.documentation = documentation
         self.name = name
         self.isInputStreaming = isInputStreaming
         self.isOutputStreaming = isOutputStreaming
         self.inputType = inputType
-        self.ouputType = ouputType
+        self.outputType = outputType
       }
     }
   }

Sources/GRPCCodeGen/Internal/StructuredSwiftRepresentation.swift

@@ -66,7 +66,6 @@ struct ImportDescription: Equatable, Codable {
 ///
 /// For example: `public`.
 internal enum AccessModifier: String, Sendable, Equatable, Codable {
-
   /// A declaration accessible outside of the module.
   case `public`
 

Sources/GRPCCodeGen/Internal/Translator/IDLToStructuredSwiftTranslator.swift

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2023, 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.
+ */
+
+struct IDLToStructuredSwiftTranslator: Translator {
+  private let typealiasTranslator = TypealiasTranslator()
+
+  func translate(
+    codeGenerationRequest: CodeGenerationRequest,
+    client: Bool,
+    server: Bool
+  ) throws -> StructuredSwiftRepresentation {
+    let topComment = Comment.doc(codeGenerationRequest.leadingTrivia)
+    let imports: [ImportDescription] = [
+      ImportDescription(moduleName: "GRPCCore")
+    ]
+    var codeBlocks: [CodeBlock] = []
+    codeBlocks.append(
+      contentsOf: try self.typealiasTranslator.translate(from: codeGenerationRequest)
+    )
+
+    let fileDescription = FileDescription(
+      topComment: topComment,
+      imports: imports,
+      codeBlocks: codeBlocks
+    )
+    let fileName = String(codeGenerationRequest.fileName.split(separator: ".")[0])
+    let file = NamedFileDescription(name: fileName, contents: fileDescription)
+    return StructuredSwiftRepresentation(file: file)
+  }
+}

Sources/GRPCCodeGen/Internal/Translator/SpecializedTranslator.swift

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2023, 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.
+ */
+
+/// Represents one responsibility of the ``Translator``: either the type aliases translation,
+/// the server code translation or the client code translation.
+protocol SpecializedTranslator {
+  /// Generates an array of ``CodeBlock`` elements that will be part of the ``StructuredSwiftRepresentation`` object
+  /// created by the ``Translator``.
+  ///
+  /// - Parameters:
+  ///   - codeGenerationRequest: The ``CodeGenerationRequest`` object used to represent a Source IDL description of RPCs.
+  /// - Returns: An array of ``CodeBlock`` elements.
+  ///
+  /// - SeeAlso: ``CodeGenerationRequest``, ``Translator``,  ``CodeBlock``.
+  func translate(from codeGenerationRequest: CodeGenerationRequest) throws -> [CodeBlock]
+}

Sources/GRPCCodeGen/Internal/Translator/Translator.swift

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2023, 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.
+ */
+
+/// Transforms ``CodeGenerationRequest`` objects into ``StructuredSwiftRepresentation`` objects.
+///
+/// It represents the first step of the code generation process for IDL described RPCs.
+protocol Translator {
+  /// Translates the provided ``CodeGenerationRequest`` object, into Swift code representation.
+  /// - Parameters:
+  ///   - codeGenerationRequest: The IDL described RPCs representation.
+  ///   - client: Whether or not client code should be generated from the IDL described RPCs representation.
+  ///   - server: Whether or not server code should be generated from the IDL described RPCs representation.
+  /// - Returns: A structured Swift representation of the generated code.
+  /// - Throws: An error if there are issues translating the codeGenerationRequest.
+  func translate(
+    codeGenerationRequest: CodeGenerationRequest,
+    client: Bool,
+    server: Bool
+  ) throws -> StructuredSwiftRepresentation
+}