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Code generation command plugin
Motivation: To make it simpler to generate gRPC stubs with `protoc-gen-grpc-swift` and `protoc-gen-swift`. Modifications: * Add a new command plugin `swift package generate-grpc-code-from-protos/path/to/Protos/HelloWorld.proto --import-path /path/to/Protos` * Refactor some errors Result: More convenient code generation
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‎Package.swift‎

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@@ -115,6 +115,27 @@ let targets: [Target] = [
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.product(name: "protoc-gen-swift", package: "swift-protobuf"),
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]
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),
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// Code generator SwiftPM command
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.plugin(
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name: "GRPCGeneratorCommand",
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capability: .command(
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intent: .custom(
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verb: "generate-grpc-code-from-protos",
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description: "Generate Swift code for gRPC services from protobuf definitions."
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),
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permissions: [
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.writeToPackageDirectory(
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reason:
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"To write the generated Swift files back into the source directory of the package."
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)
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]
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),
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dependencies: [
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"protoc-gen-grpc-swift",
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.product(name: "protoc-gen-swift", package: "swift-protobuf"),
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]
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),
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]
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let package = Package(

‎Plugins/GRPCGeneratorCommand/CommandConfig.swift‎

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/*
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* Copyright 2024, 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 Foundation
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import PackagePlugin
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struct CommandConfig {
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var common: GenerationConfig
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var dryRun: Bool
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static let defaults = Self(
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common: .init(
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accessLevel: .internal,
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servers: true,
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clients: true,
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messages: true,
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fileNaming: .fullPath,
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accessLevelOnImports: false,
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importPaths: [],
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outputPath: ""
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),
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dryRun: false
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)
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}
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extension CommandConfig {
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static func parse(
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arguments: [String],
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pluginWorkDirectory: URL
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) throws -> (CommandConfig, [String]) {
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var config = CommandConfig.defaults
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var argExtractor = ArgumentExtractor(arguments)
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for flag in Flag.allCases {
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switch flag {
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case .accessLevel:
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let accessLevel = argExtractor.extractOption(named: flag.rawValue)
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if let value = accessLevel.first {
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switch value.lowercased() {
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case "internal":
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config.common.accessLevel = .`internal`
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case "public":
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config.common.accessLevel = .`public`
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case "package":
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config.common.accessLevel = .`package`
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default:
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Diagnostics.error("Unknown accessLevel \(value)")
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}
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}
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case .servers:
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let servers = argExtractor.extractOption(named: flag.rawValue)
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if let value = servers.first {
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guard let servers = Bool(value) else {
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throw CommandPluginError.invalidArgumentValue(value)
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}
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config.common.servers = servers
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}
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case .clients:
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let clients = argExtractor.extractOption(named: flag.rawValue)
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if let value = clients.first {
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guard let clients = Bool(value) else {
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throw CommandPluginError.invalidArgumentValue(value)
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}
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config.common.clients = clients
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}
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case .messages:
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let messages = argExtractor.extractOption(named: flag.rawValue)
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if let value = messages.first {
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guard let messages = Bool(value) else {
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throw CommandPluginError.invalidArgumentValue(value)
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}
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config.common.messages = messages
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}
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case .fileNaming:
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let fileNaming = argExtractor.extractOption(named: flag.rawValue)
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if let value = fileNaming.first {
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switch value.lowercased() {
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case "fullPath":
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config.common.fileNaming = .fullPath
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case "pathToUnderscores":
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config.common.fileNaming = .pathToUnderscores
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case "dropPath":
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config.common.fileNaming = .dropPath
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default:
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Diagnostics.error("Unknown file naming strategy \(value)")
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}
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}
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case .accessLevelOnImports:
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let accessLevelOnImports = argExtractor.extractOption(named: flag.rawValue)
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if let value = accessLevelOnImports.first {
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guard let accessLevelOnImports = Bool(value) else {
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throw CommandPluginError.invalidArgumentValue(value)
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}
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config.common.accessLevelOnImports = accessLevelOnImports
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}
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case .importPath:
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config.common.importPaths = argExtractor.extractOption(named: flag.rawValue)
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case .protocPath:
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let protocPath = argExtractor.extractOption(named: flag.rawValue)
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config.common.protocPath = protocPath.first
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case .output:
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let output = argExtractor.extractOption(named: flag.rawValue)
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config.common.outputPath = output.first ?? pluginWorkDirectory.absoluteStringNoScheme
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case .dryRun:
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let dryRun = argExtractor.extractFlag(named: flag.rawValue)
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config.dryRun = dryRun != 0
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case .help:
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let help = argExtractor.extractFlag(named: flag.rawValue)
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if help != 0 {
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throw CommandPluginError.helpRequested
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}
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}
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}
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if argExtractor.remainingArguments.isEmpty {
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throw CommandPluginError.missingInputFile
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}
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for argument in argExtractor.remainingArguments {
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if argument.hasPrefix("--") {
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throw CommandPluginError.unknownOption(argument)
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}
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}
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return (config, argExtractor.remainingArguments)
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}
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}
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/// All valid input options/flags
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enum Flag: CaseIterable, RawRepresentable {
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typealias RawValue = String
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case servers
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case clients
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case messages
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case fileNaming
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case accessLevel
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case accessLevelOnImports
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case importPath
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case protocPath
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case output
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case dryRun
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case help
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init?(rawValue: String) {
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switch rawValue {
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case "servers":
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self = .servers
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case "clients":
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self = .clients
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case "messages":
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self = .messages
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case "file-naming":
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self = .fileNaming
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case "access-level":
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self = .accessLevel
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case "use-access-level-on-imports":
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self = .accessLevelOnImports
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case "import-path":
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self = .importPath
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case "protoc-path":
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self = .protocPath
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case "output":
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self = .output
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case "dry-run":
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self = .dryRun
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case "help":
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self = .help
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default:
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return nil
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}
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return nil
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}
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var rawValue: String {
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switch self {
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case .servers:
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"servers"
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case .clients:
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"clients"
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case .messages:
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"messages"
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case .fileNaming:
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"file-naming"
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case .accessLevel:
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"access-level"
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case .accessLevelOnImports:
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"access-level-on-imports"
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case .importPath:
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"import-path"
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case .protocPath:
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"protoc-path"
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case .output:
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"output"
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case .dryRun:
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"dry-run"
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case .help:
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"help"
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}
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}
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}
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extension Flag {
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func usageDescription() -> String {
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switch self {
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case .servers:
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return "Whether server code is generated. Defaults to true."
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case .clients:
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return "Whether client code is generated. Defaults to true."
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case .messages:
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return "Whether message code is generated. Defaults to true."
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case .fileNaming:
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return
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"The naming scheme for output files [fullPath/pathToUnderscores/dropPath]. Defaults to fullPath."
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case .accessLevel:
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return
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"The access level of the generated source [internal/public/package]. Defaults to internal."
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case .accessLevelOnImports:
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return "Whether imports should have explicit access levels. Defaults to false."
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case .importPath:
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return "The directory in which to search for imports."
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case .protocPath:
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return "The path to the `protoc` binary."
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case .dryRun:
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return "Print but do not execute the protoc commands."
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case .output:
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return "The path into which the generated source files are created."
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case .help:
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return "Print this help."
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}
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}
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static func printHelp() {
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print("Usage: swift package generate-grpc-code-from-protos [flags] [input files]")
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print("")
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print("Flags:")
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print("")
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let spacing = 3
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let maxLength =
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(Flag.allCases.map(\.rawValue).max(by: { $0.count < $1.count })?.count ?? 0) + spacing
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for flag in Flag.allCases {
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print(
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" --\(flag.rawValue.padding(toLength: maxLength, withPad: " ", startingAt: 0))\(flag.usageDescription())"
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)
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}
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}
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}

‎Plugins/GRPCGeneratorCommand/CommandPluginError.swift‎

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/*
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* Copyright 2025, 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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enum CommandPluginError: Error {
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case helpRequested
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case missingArgumentValue
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case invalidArgumentValue(String)
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case missingInputFile
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case unknownOption(String)
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}
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extension CommandPluginError: CustomStringConvertible {
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var description: String {
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switch self {
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case .helpRequested:
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"User requested help."
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case .missingArgumentValue:
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"Provided option does not have a value."
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case .invalidArgumentValue:
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"Invalid option value."
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case .missingInputFile:
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"No input file(s) specified."
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case .unknownOption(let value):
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"Provided option is unknown: \(value)."
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}
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}
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}

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