Add WebAssembly SDK recipe and make-wasm-sdk subcommand (#74)

* Add WebAssembly SDK recipe and `make-wasm-sdk` subcommand

This patch introduces an experimental WebAssembly SDK recipe and `make-wasm-sdk`
subcommand. The make command takes host Swift toolchain package, target
Swift stdlib (`lib/swift{,_static}`), and WASI sysroot like follows:

```console
swift run swift-sdk-generator make-wasm-sdk \
  --target wasm32-unknown-wasi \
  --host-swift-package-path Downloads/swift-DEVELOPMENT-SNAPSHOT-2024-01-12-a \
  --target-swift-package-path Downloads/swift-wasm-DEVELOPMENT-SNAPSHOT-2024-01-12-a \
  --wasi-sysroot Downloads/wasi-sysroot
```

* Use `GeneratorOptions`'s common fields

* rsync `lib/clang` into the SDK bundle

The directory was missed to be taken from target toolchain but it wasn't
revealed on local testing since the host toolchain unintentionally
contained the directory.

---------

Co-authored-by: Max Desiatov <[email protected]>

Sources/GeneratorCLI/GeneratorCLI.swift

@@ -14,12 +14,13 @@ import ArgumentParser
 import Logging
 import ServiceLifecycle
 import SwiftSDKGenerator
+import struct SystemPackage.FilePath
 
 @main
 struct GeneratorCLI: AsyncParsableCommand {
   static let configuration = CommandConfiguration(
     commandName: "swift-sdk-generator",
-    subcommands: [MakeLinuxSDK.self],
+    subcommands: [MakeLinuxSDK.self, MakeWasmSDK.self],
     defaultSubcommand: MakeLinuxSDK.self
   )
 
@@ -238,6 +239,46 @@ extension GeneratorCLI {
       return false
     }
   }
+
+  struct MakeWasmSDK: AsyncParsableCommand {
+    static let configuration = CommandConfiguration(
+      commandName: "make-wasm-sdk",
+      abstract: "Experimental: Generate a Swift SDK bundle for WebAssembly.",
+      discussion: """
+      The default `--target` triple is wasm32-unknown-wasi
+      """
+    )
+
+    @OptionGroup
+    var generatorOptions: GeneratorOptions
+
+    @Option(
+      help: """
+      Path to the WASI sysroot directory containing the WASI libc headers and libraries.
+      """
+    )
+    var wasiSysroot: String
+
+    func deriveTargetTriple(hostTriple: Triple) -> Triple {
+      self.generatorOptions.target ?? Triple("wasm32-unknown-wasi")
+    }
+
+    func run() async throws {
+      guard let hostSwiftPackagePath = generatorOptions.hostSwiftPackagePath,
+            let targetSwiftPackagePath = generatorOptions.targetSwiftPackagePath else {
+        throw StringError("Missing expected argument '--host-swift-package-path' or '--target-swift-package-path'")
+      }
+      let recipe = WebAssemblyRecipe(
+        hostSwiftPackagePath: FilePath(hostSwiftPackagePath),
+        targetSwiftPackagePath: FilePath(targetSwiftPackagePath),
+        wasiSysroot: FilePath(wasiSysroot),
+        swiftVersion: generatorOptions.swiftVersion
+      )
+      let hostTriple = try self.generatorOptions.deriveHostTriple()
+      let targetTriple = self.deriveTargetTriple(hostTriple: hostTriple)
+      try await GeneratorCLI.run(recipe: recipe, hostTriple: hostTriple, targetTriple: targetTriple, options: generatorOptions)
+    }
+  }
 }
 
 // FIXME: replace this with a call on `.formatted()` on `Duration` when it's available in swift-foundation.
@@ -269,3 +310,10 @@ struct SwiftSDKGeneratorService: Service {
         try await generator.run(recipe: recipe)
     }
 }
+
+struct StringError: Error, CustomStringConvertible {
+  let description: String
+  init(_ description: String) {
+    self.description = description
+  }
+}

Sources/SwiftSDKGenerator/Generator/SwiftSDKGenerator.swift

@@ -167,6 +167,11 @@ public actor SwiftSDKGenerator {
     try await Shell.run("rsync -a \(source) \(destination)", shouldLogCommands: self.isVerbose)
   }
 
+  func rsyncContents(from source: FilePath, to destination: FilePath) async throws {
+    try self.createDirectoryIfNeeded(at: destination)
+    try await Shell.run("rsync -a \(source)/ \(destination)", shouldLogCommands: self.isVerbose)
+  }
+
   func createSymlink(at source: FilePath, pointingTo destination: FilePath) throws {
     try self.fileManager.createSymbolicLink(
       atPath: source.string,

Sources/SwiftSDKGenerator/SwiftSDKRecipes/WebAssemblyRecipe.swift

@@ -0,0 +1,82 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2022-2024 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 AsyncHTTPClient
+import GeneratorEngine
+import struct SystemPackage.FilePath
+
+public struct WebAssemblyRecipe: SwiftSDKRecipe {
+  let hostSwiftPackagePath: FilePath
+  let targetSwiftPackagePath: FilePath
+  let wasiSysroot: FilePath
+  let swiftVersion: String
+
+  public init(
+    hostSwiftPackagePath: FilePath,
+    targetSwiftPackagePath: FilePath,
+    wasiSysroot: FilePath,
+    swiftVersion: String
+  ) {
+    self.hostSwiftPackagePath = hostSwiftPackagePath
+    self.targetSwiftPackagePath = targetSwiftPackagePath
+    self.wasiSysroot = wasiSysroot
+    self.swiftVersion = swiftVersion
+  }
+
+  public var defaultArtifactID: String {
+    "\(self.swiftVersion)_wasm"
+  }
+
+  public func applyPlatformOptions(toolset: inout Toolset) {
+    // We only support static linking for WebAssembly for now, so make it the default.
+    toolset.swiftCompiler = Toolset.ToolProperties(extraCLIOptions: ["-static-stdlib"])
+  }
+
+  public func makeSwiftSDK(
+    generator: SwiftSDKGenerator,
+    engine: Engine,
+    httpClient: HTTPClient
+  ) async throws -> SwiftSDKProduct {
+    let pathsConfiguration = generator.pathsConfiguration
+    logGenerationStep("Copying Swift binaries for the host triple...")
+    try await generator.rsync(from: self.hostSwiftPackagePath.appending("usr"), to: pathsConfiguration.toolchainDirPath)
+    try await self.copyTargetSwift(from: self.targetSwiftPackagePath.appending("usr/lib"), generator: generator)
+
+    let autolinkExtractPath = generator.pathsConfiguration.toolchainBinDirPath.appending("swift-autolink-extract")
+
+    // WebAssembly object file requires `swift-autolink-extract`
+    if await !generator.doesFileExist(at: autolinkExtractPath) {
+      logGenerationStep("Fixing `swift-autolink-extract` symlink...")
+      try await generator.createSymlink(at: autolinkExtractPath, pointingTo: "swift")
+    }
+
+    // Copy the WASI sysroot into the SDK bundle.
+    let sdkDirPath = pathsConfiguration.swiftSDKRootPath.appending("WASI.sdk")
+    try await generator.rsyncContents(from: self.wasiSysroot, to: sdkDirPath)
+
+    return SwiftSDKProduct(sdkDirPath: sdkDirPath)
+  }
+
+  func copyTargetSwift(from distributionPath: FilePath, generator: SwiftSDKGenerator) async throws {
+    let pathsConfiguration = generator.pathsConfiguration
+    logGenerationStep("Copying Swift core libraries for the target triple into Swift SDK bundle...")
+    for (pathWithinPackage, pathWithinSwiftSDK) in [
+      ("clang", pathsConfiguration.toolchainDirPath.appending("usr/lib")),
+      ("swift/wasi", pathsConfiguration.toolchainDirPath.appending("usr/lib/swift")),
+      ("swift_static/wasi", pathsConfiguration.toolchainDirPath.appending("usr/lib/swift_static")),
+      ("swift_static/shims", pathsConfiguration.toolchainDirPath.appending("usr/lib/swift_static")),
+      ("swift_static/CoreFoundation", pathsConfiguration.toolchainDirPath.appending("usr/lib/swift_static")),
+    ] {
+      try await generator.rsync(from: distributionPath.appending(pathWithinPackage), to: pathWithinSwiftSDK)
+    }
+  }
+}