SE-0466: Add support for -default-isolation flag

Author: xedin

Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift

@@ -311,6 +311,9 @@ extension Driver {
     if isFrontendArgSupported(.strictConcurrency) {
       try commandLine.appendLast(.strictConcurrency, from: &parsedOptions)
     }
+    if isFrontendArgSupported(.defaultIsolation) {
+      try commandLine.appendLast(.defaultIsolation, from: &parsedOptions)
+    }
     if kind == .scanDependencies,
         isFrontendArgSupported(.experimentalClangImporterDirectCc1Scan) {
       try commandLine.appendAll(

Sources/SwiftOptions/Options.swift

@@ -134,6 +134,8 @@ extension Option {
   public static let debugTimeFunctionBodies: Option = Option("-debug-time-function-bodies", .flag, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Dumps the time it takes to type-check each function body")
   public static let debuggerSupport: Option = Option("-debugger-support", .flag, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Process swift code as if running in the debugger")
   public static let debuggerTestingTransform: Option = Option("-debugger-testing-transform", .flag, attributes: [.helpHidden, .frontend, .noDriver], helpText: "Instrument the code with calls to an intrinsic that record the expected values of local variables so they can be compared against the results from the debugger.")
+  public static let defaultIsolationEQ: Option = Option("-default-isolation=", .joined, alias: Option.defaultIsolation, attributes: [.frontend])
+  public static let defaultIsolation: Option = Option("-default-isolation", .separate, attributes: [.frontend], metaVar: "MainActor|nonisolated", helpText: "Specify the default actor isolation: MainActor or nonisolated. Defaults to nonisolated.")
   public static let defineAvailability: Option = Option("-define-availability", .separate, attributes: [.frontend, .noInteractive], metaVar: "<macro>", helpText: "Define an availability macro in the format 'macroName : iOS 13.0, macOS 10.15'")
   public static let defineDisabledAvailabilityDomain: Option = Option("-define-disabled-availability-domain", .separate, attributes: [.helpHidden, .frontend, .noInteractive], metaVar: "<domain>", helpText: "Defines a custom availability domain that is unavailable at compile time")
   public static let defineDynamicAvailabilityDomain: Option = Option("-define-dynamic-availability-domain", .separate, attributes: [.helpHidden, .frontend, .noInteractive], metaVar: "<domain>", helpText: "Defines a custom availability domain that can be enabled or disabled at runtime")
@@ -1079,6 +1081,8 @@ extension Option {
       Option.debugTimeFunctionBodies,
       Option.debuggerSupport,
       Option.debuggerTestingTransform,
+      Option.defaultIsolationEQ,
+      Option.defaultIsolation,
       Option.defineAvailability,
       Option.defineDisabledAvailabilityDomain,
       Option.defineDynamicAvailabilityDomain,

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -3935,6 +3935,18 @@ final class SwiftDriverTests: XCTestCase {
     XCTAssertTrue(plannedJobs[0].commandLine.contains(.flag("-disable-dynamic-actor-isolation")))
   }
 
+  func testDefaultIsolation() throws {
+      var driver = try Driver(args: ["swiftc", "test.swift", "-default-isolation", "MainActor"])
+      guard driver.isFrontendArgSupported(.defaultIsolation) else {
+        throw XCTSkip("Skipping: compiler does not support '-default-isolation'")
+      }
+      let plannedJobs = try driver.planBuild().removingAutolinkExtractJobs()
+      XCTAssertEqual(plannedJobs.count, 2)
+      XCTAssertEqual(plannedJobs[0].kind, .compile)
+      XCTAssertEqual(plannedJobs[1].kind, .link)
+      try XCTAssertJobInvocationMatches(plannedJobs[0], .flag("-default-isolation"), "MainActor")
+  }
+
   func testImmediateMode() throws {
     do {
       var driver = try Driver(args: ["swift", "foo.swift"])