Add help intro

Add an "intro" topic to swift-help, printing the version, welcome message, and
available subcommands.

When running `swift` by itself, show the intro before entering the REPL.

When running `swift-help` directly or via `swift --help`, show all of the
available flags as previously.

rdar://78280423

Author: bitjammer

Sources/SwiftDriver/CMakeLists.txt

@@ -75,6 +75,7 @@ add_library(SwiftDriver
   Jobs/Planning.swift
   Jobs/PrintTargetInfoJob.swift
   Jobs/ReplJob.swift
+  Jobs/SwiftHelpIntroJob.swift
   Jobs/Toolchain+InterpreterSupport.swift
   Jobs/Toolchain+LinkerSupport.swift
   Jobs/VerifyDebugInfoJob.swift

Sources/SwiftDriver/Driver/CompilerMode.swift

@@ -32,6 +32,9 @@
 
   /// Dump information about a precompiled Clang module
   case dumpPCM
+
+  /// Introduce the user to Swift concepts depending on context.
+  case intro
 }
 
 /// Information about batch mode, which is used to determine how to form
@@ -46,7 +49,7 @@ extension CompilerMode {
   /// Whether this compilation mode uses -primary-file to specify its inputs.
   public var usesPrimaryFileInputs: Bool {
     switch self {
-    case .immediate, .repl, .singleCompile, .compilePCM, .dumpPCM:
+    case .immediate, .repl, .singleCompile, .compilePCM, .dumpPCM, .intro:
       return false
 
     case .standardCompile, .batchCompile:
@@ -57,7 +60,7 @@ extension CompilerMode {
   /// Whether this compilation mode compiles the whole target in one job.
   public var isSingleCompilation: Bool {
     switch self {
-    case .immediate, .repl, .standardCompile, .batchCompile:
+    case .immediate, .repl, .standardCompile, .batchCompile, .intro:
       return false
 
     case .singleCompile, .compilePCM, .dumpPCM:
@@ -67,7 +70,7 @@ extension CompilerMode {
 
   public var isStandardCompilationForPlanning: Bool {
     switch self {
-      case .immediate, .repl, .compilePCM, .dumpPCM:
+    case .immediate, .repl, .compilePCM, .dumpPCM, .intro:
         return false
       case .batchCompile, .standardCompile, .singleCompile:
         return true
@@ -93,7 +96,7 @@ extension CompilerMode {
     switch self {
     case .batchCompile, .singleCompile, .standardCompile, .compilePCM, .dumpPCM:
       return true
-    case .immediate, .repl:
+    case .immediate, .repl, .intro:
       return false
     }
   }
@@ -116,6 +119,8 @@ extension CompilerMode: CustomStringConvertible {
         return "compile Clang module (.pcm)"
       case .dumpPCM:
         return "dump Clang module (.pcm)"
+      case .intro:
+        return "introduction to Swift and packages"
       }
   }
 }

Sources/SwiftDriver/Driver/Driver.swift

@@ -804,6 +804,7 @@ extension Driver {
     // If it is the "built-in" 'repl', then use the normal driver.
     if firstArg == "repl" {
         updatedArgs.remove(at: 1)
+        updatedArgs.append("-repl")
         return (.normal(isRepl: true), updatedArgs)
     }
 
@@ -1401,7 +1402,15 @@ extension Driver {
     }
 
     if driverKind == .interactive {
-      return parsedOptions.hasAnyInput ? .immediate : .repl
+      if parsedOptions.hasAnyInput {
+        return .immediate
+      } else {
+        if parsedOptions.contains(Option.repl) {
+          return .repl
+        } else {
+          return .intro
+        }
+      }
     }
 
     let useWMO = parsedOptions.hasFlag(positive: .wholeModuleOptimization, negative: .noWholeModuleOptimization, default: false)
@@ -1996,7 +2005,7 @@ extension Driver {
     }
 
     // The REPL and immediate mode do not support module output
-    if moduleOutputKind != nil && (compilerMode == .repl || compilerMode == .immediate) {
+    if moduleOutputKind != nil && (compilerMode == .repl || compilerMode == .immediate || compilerMode == .intro) {
       diagnosticsEngine.emit(.error_mode_cannot_emit_module)
       moduleOutputKind = nil
     }
@@ -2006,7 +2015,9 @@ extension Driver {
     var moduleNameIsFallback = false
     if let arg = parsedOptions.getLastArgument(.moduleName) {
       moduleName = arg.asSingle
-    } else if compilerMode == .repl {
+    } else if compilerMode == .repl || compilerMode == .intro {
+      // TODO: Remove the `.intro` check once the REPL no longer launches
+      // by default.
       // REPL mode should always use the REPL module.
       moduleName = "REPL"
     } else if let outputArg = parsedOptions.getLastArgument(.o) {

Sources/SwiftDriver/IncrementalCompilation/IncrementalCompilationState.swift

@@ -180,7 +180,7 @@ fileprivate extension CompilerMode {
   var supportsIncrementalCompilation: Bool {
     switch self {
     case .standardCompile, .immediate, .repl, .batchCompile: return true
-    case .singleCompile, .compilePCM, .dumpPCM: return false
+    case .singleCompile, .compilePCM, .dumpPCM, .intro: return false
     }
   }
 }

Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift

@@ -64,6 +64,8 @@ extension Driver {
         commandLine.appendFlag(.target)
         commandLine.appendFlag(targetTriple.triple)
       }
+    case .intro:
+      break
     }
 
     // Pass down -clang-target.
@@ -269,7 +271,7 @@ extension Driver {
     }
 
     // Repl Jobs shouldn't include -module-name.
-    if compilerMode != .repl {
+    if compilerMode != .repl && compilerMode != .intro {
       commandLine.appendFlags("-module-name", moduleOutputInfo.name)
     }
 

Sources/SwiftDriver/Jobs/Planning.swift

@@ -668,7 +668,7 @@ extension Driver {
     }
 
     // The REPL doesn't require input files, but all other modes do.
-    guard !inputFiles.isEmpty || compilerMode == .repl else {
+    guard !inputFiles.isEmpty || compilerMode == .repl || compilerMode == .intro else {
       if parsedOptions.hasArgument(.v) {
         // `swiftc -v` is allowed and prints version information.
         return ([], nil)
@@ -704,6 +704,20 @@ extension Driver {
         throw PlanningError.dumpPCMWrongInputFiles
       }
       return ([try generateDumpPCMJob(input: inputFiles.first!)], nil)
+    case .intro:
+      // TODO: Remove this check once the REPL no longer launches
+      // by default.
+      if !inputFiles.isEmpty {
+        throw PlanningError.replReceivedInput
+      }
+      // end TODO.
+
+      var introJobs = try helpIntroJobs()
+
+      // TODO: Remove this to stop launching the REPL by default.
+      introJobs.append(try replJob())
+
+      return (introJobs, nil)
     }
   }
 }

Sources/SwiftDriver/Jobs/SwiftHelpIntroJob.swift

@@ -0,0 +1,38 @@
+//===--------------- SwiftHelpIntroJob.swift - Swift REPL -----------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+import SwiftOptions
+
+extension Driver {
+  mutating func helpIntroJobs() throws -> [Job] {
+    return [
+      Job(
+        moduleName: moduleOutputInfo.name,
+        kind: .versionRequest,
+        tool: .absolute(try toolchain.getToolPath(.swiftCompiler)),
+        commandLine: [.flag("--version")],
+        inputs: [],
+        primaryInputs: [],
+        outputs: [],
+        requiresInPlaceExecution: false),
+      Job(
+        moduleName: moduleOutputInfo.name,
+        kind: .help,
+        tool: .absolute(try toolchain.getToolPath(.swiftHelp)),
+        commandLine: [.flag("intro")],
+        inputs: [],
+        primaryInputs: [],
+        outputs: [],
+        requiresInPlaceExecution: false
+      ),
+    ]
+  }
+}

Sources/swift-help/main.swift

@@ -16,12 +16,15 @@ import ArgumentParser
 enum HelpTopic: ExpressibleByArgument, CustomStringConvertible {
   case driver(DriverKind)
   case subcommand(Subcommand)
+  case intro
 
   init?(argument topicName: String) {
     if let kind = DriverKind(rawValue: topicName) {
       self = .driver(kind)
     } else if let subcommand = Subcommand(rawValue: topicName) {
       self = .subcommand(subcommand)
+    } else if topicName == "intro" {
+      self = .intro
     } else {
       return nil
     }
@@ -33,6 +36,8 @@ enum HelpTopic: ExpressibleByArgument, CustomStringConvertible {
       return kind.rawValue
     case .subcommand(let command):
       return command.rawValue
+    case .intro:
+      return "intro"
     }
   }
 }
@@ -43,13 +48,13 @@ enum Subcommand: String, CaseIterable {
   var description: String {
     switch self {
     case .build:
-      return "SwiftPM - Build sources into binary products"
+      return "Build Swift packages"
     case .package:
-      return "SwiftPM - Perform operations on Swift packages"
+      return "Create and work on packages"
     case .run:
-      return "SwiftPM - Build and run an executable product"
+      return "Run a program from a package"
     case .test:
-      return "SwiftPM - Build and run tests"
+      return "Run package tests"
     }
   }
 }
@@ -65,19 +70,60 @@ struct SwiftHelp: ParsableCommand {
         help: "List hidden (unsupported) options")
   var showHidden: Bool = false
 
+  enum Color256: CustomStringConvertible {
+    case reset
+    case color(foreground: UInt8?, background: UInt8?)
+
+    var description: String {
+      switch self {
+      case .reset:
+        return "\u{001B}[0m"
+      case let .color(foreground, background):
+        let foreground = foreground.map { "\u{001B}[38;5;\($0)m" } ?? ""
+        let background = background.map { "\u{001B}[48;5;\($0)m" } ?? ""
+        return foreground + background
+      }
+    }
+  }
+
+  func printIntro() {
+    let is256Color = ProcessEnv.vars["TERM"] == "xterm-256color"
+    let orangeRed = is256Color ? "\u{001b}[1;38;5;196m" : ""
+    let plain = is256Color ? "\u{001b}[0m" : ""
+    let plainBold = is256Color ? "\u{001b}[1m" : ""
+
+    print("""
+
+    \(orangeRed)Welcome to Swift!\(plain)
+
+    \(plainBold)Subcommands:\(plain)
+
+    """)
+
+    let maxSubcommandNameLength = Subcommand.allCases.map { $0.rawValue.count }.max()!
+
+    for command in Subcommand.allCases {
+      let padding = String(repeating: " ", count: maxSubcommandNameLength - command.rawValue.count)
+      print("  \(plainBold)swift \(command.rawValue)\(plain)\(padding)    \(command.description)")
+    }
+
+    // `repl` not included in `Subcommand`, also print it here.
+    do {
+      let padding = String(repeating: " ", count: maxSubcommandNameLength - "repl".count)
+      print("  \(plainBold)swift repl\(plain)\(padding)    Experiment with Swift code interactively (default)")
+    }
+
+    print("\n  Use \(plainBold)`swift --help`\(plain) for descriptions of available options and flags.")
+    print("\n  Use \(plainBold)`swift help <subcommand>`\(plain) for more information about a subcommand.")
+    print()
+  }
+
   func run() throws {
     let driverOptionTable = OptionTable()
     switch topic {
     case .driver(let kind):
       driverOptionTable.printHelp(driverKind: kind, includeHidden: showHidden)
-      print("\nSUBCOMMANDS (swift <subcommand> [arguments]):")
-      let maxSubcommandNameLength = Subcommand.allCases.map(\.rawValue.count).max()!
-      for subcommand in Subcommand.allCases {
-        let padding = String(repeating: " ", count: maxSubcommandNameLength - subcommand.rawValue.count)
-        print("  \(subcommand.rawValue):\(padding) \(subcommand.description)")
-      }
-      print("\n  Use \"swift help <subcommand>\" for more information about a subcommand")
-
+      printIntro()
     case .subcommand(let subcommand):
       // Try to find the subcommand adjacent to the help tool.
       // If we didn't find the tool there, let the OS search for it.
@@ -98,6 +144,8 @@ struct SwiftHelp: ParsableCommand {
       } else {
         try exec(path: path.pathString, args: [execName, "help"] + subtopics)
       }
+    case .intro:
+      printIntro()
     }
   }
 }

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -60,7 +60,7 @@ final class SwiftDriverTests: XCTestCase {
 
     let driver5 = try Driver.invocationRunMode(forArgs: ["swift", "repl"])
     XCTAssertEqual(driver5.mode, .normal(isRepl: true))
-    XCTAssertEqual(driver5.args, ["swift"])
+    XCTAssertEqual(driver5.args, ["swift", "-repl"])
 
     let driver6 = try Driver.invocationRunMode(forArgs: ["swift", "foo", "bar"])
     XCTAssertEqual(driver6.mode, .subcommand("swift-foo"))
@@ -125,7 +125,7 @@ final class SwiftDriverTests: XCTestCase {
       XCTAssertEqual(driver1.compilerMode, .immediate)
 
       let driver2 = try Driver(args: ["swift"])
-      XCTAssertEqual(driver2.compilerMode, .repl)
+      XCTAssertEqual(driver2.compilerMode, .intro)
     }
 
     do {
@@ -2295,8 +2295,17 @@ final class SwiftDriverTests: XCTestCase {
     do {
       var driver = try Driver(args: ["swift"])
       let plannedJobs = try driver.planBuild()
-      XCTAssertEqual(plannedJobs.count, 1)
-      let replJob = plannedJobs.first!
+      XCTAssertEqual(plannedJobs.count, 3)
+
+      let versionJob = plannedJobs[0]
+      XCTAssertTrue(versionJob.tool.name.contains("swift"))
+      XCTAssertTrue(versionJob.commandLine.contains(.flag("--version")))
+
+      let helpJob = plannedJobs[1]
+      XCTAssertTrue(helpJob.tool.name.contains("swift-help"))
+      XCTAssertTrue(helpJob.commandLine.contains(.flag("intro")))
+
+      let replJob = plannedJobs[2]
       XCTAssertTrue(replJob.tool.name.contains("lldb"))
       XCTAssertTrue(replJob.requiresInPlaceExecution)
       XCTAssert(replJob.commandLine.contains(where: { isExpectedLLDBREPLFlag($0) }))