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Code generation for async-await (#1259)
Motivation: Manually constructing clients and servers is an error prone nightmare. We should generate them instead! Modifications: - Add async-await code-generation for server and client. - The client code generation is missing "simple-safe" wrappers for now, this can be added later. - Naming represents the current state of the branch rather than anything final - Add options for "ExperimentalAsyncClient" and "ExperimentalAsyncServer" -- these may be used in conjunction with the 'regular' "Client" and "Server" options. Result: We can generate async-await style grpc clients and servers.
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‎Sources/protoc-gen-grpc-swift/Generator-Client+AsyncAwait.swift

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/*
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* Copyright 2021, gRPC Authors All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import SwiftProtobuf
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import SwiftProtobufPluginLibrary
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// MARK: - Client protocol
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extension Generator {
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internal func printAsyncServiceClientProtocol() {
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let comments = self.service.protoSourceComments()
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if !comments.isEmpty {
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// Source comments already have the leading '///'
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self.println(comments, newline: false)
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}
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self.printAvailabilityForAsyncAwait()
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self.println("\(self.access) protocol \(self.asyncClientProtocolName): GRPCClient {")
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self.withIndentation {
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self.println("var serviceName: String { get }")
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self.println("var interceptors: \(self.clientInterceptorProtocolName)? { get }")
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for method in service.methods {
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self.println()
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self.method = method
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let rpcType = streamingType(self.method)
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let callType = Types.call(for: rpcType)
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let arguments: [String]
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switch rpcType {
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case .unary, .serverStreaming:
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arguments = [
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"_ request: \(self.methodInputName)",
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"callOptions: \(Types.clientCallOptions)?",
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]
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case .clientStreaming, .bidirectionalStreaming:
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arguments = [
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"callOptions: \(Types.clientCallOptions)?",
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]
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}
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self.printFunction(
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name: "make\(self.method.name)Call",
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arguments: arguments,
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returnType: "\(callType)<\(self.methodInputName), \(self.methodOutputName)>",
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bodyBuilder: nil
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)
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}
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}
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self.println("}") // protocol
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}
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}
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// MARK: - Client protocol default implementation: Calls
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extension Generator {
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internal func printAsyncClientProtocolExtension() {
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self.printAvailabilityForAsyncAwait()
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self.withIndentation("extension \(self.asyncClientProtocolName)", braces: .curly) {
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// Service name. TODO: use static metadata.
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self.withIndentation("\(self.access) var serviceName: String", braces: .curly) {
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self.println("return \"\(self.servicePath)\"")
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}
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self.println()
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// Interceptor factory.
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self.withIndentation(
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"\(self.access) var interceptors: \(self.clientInterceptorProtocolName)?",
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braces: .curly
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) {
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self.println("return nil")
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}
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// 'Unsafe' calls.
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for method in self.service.methods {
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self.println()
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self.method = method
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let rpcType = streamingType(self.method)
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let callType = Types.call(for: rpcType)
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let callTypeWithoutPrefix = Types.call(for: rpcType, withGRPCPrefix: false)
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switch rpcType {
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case .unary, .serverStreaming:
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self.printFunction(
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name: "make\(self.method.name)Call",
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arguments: [
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"_ request: \(self.methodInputName)",
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"callOptions: \(Types.clientCallOptions)? = nil",
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],
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returnType: "\(callType)<\(self.methodInputName), \(self.methodOutputName)>",
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access: self.access
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) {
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self.withIndentation("return self.make\(callTypeWithoutPrefix)", braces: .round) {
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self.println("path: \(self.methodPath),")
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self.println("request: request,")
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self.println("callOptions: callOptions ?? self.defaultCallOptions")
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}
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}
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case .clientStreaming, .bidirectionalStreaming:
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self.printFunction(
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name: "make\(self.method.name)Call",
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arguments: ["callOptions: \(Types.clientCallOptions)? = nil"],
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returnType: "\(callType)<\(self.methodInputName), \(self.methodOutputName)>",
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access: self.access
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) {
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self.withIndentation("return self.make\(callTypeWithoutPrefix)", braces: .round) {
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self.println("path: \(self.methodPath),")
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self.println("callOptions: callOptions ?? self.defaultCallOptions")
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}
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}
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}
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}
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}
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}
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}
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// MARK: - Client protocol implementation
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extension Generator {
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internal func printAsyncServiceClientImplementation() {
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self.printAvailabilityForAsyncAwait()
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self.withIndentation(
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"\(self.access) struct \(self.asyncClientClassName): \(self.asyncClientProtocolName)",
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braces: .curly
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) {
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self.println("\(self.access) var channel: GRPCChannel")
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self.println("\(self.access) var defaultCallOptions: CallOptions")
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self.println("\(self.access) var interceptors: \(self.clientInterceptorProtocolName)?")
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self.println()
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self.println("\(self.access) init(")
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self.withIndentation {
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self.println("channel: GRPCChannel,")
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self.println("defaultCallOptions: CallOptions = CallOptions(),")
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self.println("interceptors: \(self.clientInterceptorProtocolName)? = nil")
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}
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self.println(") {")
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self.withIndentation {
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self.println("self.channel = channel")
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self.println("self.defaultCallOptions = defaultCallOptions")
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self.println("self.interceptors = interceptors")
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}
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self.println("}")
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}
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}
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}

‎Sources/protoc-gen-grpc-swift/Generator-Client.swift

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Original file line numberDiff line numberDiff line change
@@ -30,6 +30,18 @@ extension Generator {
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self.printServiceClientImplementation()
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}
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if self.options.generateAsyncClient {
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self.println()
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self.printIfCompilerGuardForAsyncAwait()
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self.printAsyncServiceClientProtocol()
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self.println()
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self.printAsyncClientProtocolExtension()
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self.println()
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self.printAsyncServiceClientImplementation()
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self.println()
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self.printEndCompilerGuardForAsyncAwait()
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}
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if self.options.generateTestClient {
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self.println()
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self.printTestClient()
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arguments: [String],
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returnType: String?,
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access: String? = nil,
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sendable: Bool = false,
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async: Bool = false,
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throws: Bool = false,
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genericWhereClause: String? = nil,
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bodyBuilder: (() -> Void)?
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) {
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// Add a space after access, if it exists.
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let accessOrEmpty = access.map { $0 + " " } ?? ""
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let `return` = returnType.map { "-> " + $0 } ?? ""
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let functionHead = (access.map { $0 + " " } ?? "") + (sendable ? "@Sendable " : "")
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let `return` = returnType.map { " -> " + $0 } ?? ""
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let genericWhere = genericWhereClause.map { " " + $0 } ?? ""
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let asyncThrows: String
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switch (async, `throws`) {
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case (true, true):
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asyncThrows = " async throws"
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case (true, false):
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asyncThrows = " async"
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case (false, true):
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asyncThrows = " throws"
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case (false, false):
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asyncThrows = ""
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}
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let hasBody = bodyBuilder != nil
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if arguments.isEmpty {
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// Don't bother splitting across multiple lines if there are no arguments.
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self.println("\(accessOrEmpty)func \(name)() \(`return`)", newline: !hasBody)
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self.println(
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"\(functionHead)func \(name)()\(asyncThrows)\(`return`)\(genericWhere)",
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newline: !hasBody
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)
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} else {
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self.println("\(accessOrEmpty)func \(name)(")
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self.println("\(functionHead)func \(name)(")
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self.withIndentation {
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// Add a comma after each argument except the last.
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arguments.forEach(beforeLast: {
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self.println($0)
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})
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}
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self.println(") \(`return`)", newline: !hasBody)
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self.println(")\(asyncThrows)\(`return`)\(genericWhere)", newline: !hasBody)
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}
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if let bodyBuilder = bodyBuilder {

‎Sources/protoc-gen-grpc-swift/Generator-Names.swift

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@@ -74,10 +74,18 @@ extension Generator {
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return nameForPackageService(file, service) + "Provider"
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}
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internal var asyncProviderName: String {
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return nameForPackageService(file, service) + "AsyncProvider"
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}
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internal var clientClassName: String {
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return nameForPackageService(file, service) + "Client"
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}
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internal var asyncClientClassName: String {
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return nameForPackageService(file, service) + "AsyncClient"
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}
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internal var testClientClassName: String {
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return nameForPackageService(self.file, self.service) + "TestClient"
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}
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return nameForPackageService(file, service) + "ClientProtocol"
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}
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internal var asyncClientProtocolName: String {
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return nameForPackageService(file, service) + "AsyncClientProtocol"
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}
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internal var clientInterceptorProtocolName: String {
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return nameForPackageService(file, service) + "ClientInterceptorFactoryProtocol"
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}

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