Support running tests that require building with a Swift 5.10 toolchain

When we detect that we’re running using a 5.10 toolchain, adjust the compiler arguments that we received from SwiftPM to drop any `/Modules` suffixes in the build directory, to account for the fact that 5.10 stores the modules one directory higher up (swiftlang/swift-package-manager#7103).

Author: ahoppen

Sources/SKSwiftPMWorkspace/SwiftPMBuildSystem.swift

@@ -357,11 +357,30 @@ extension SwiftPMBuildSystem: SKCore.BuildSystem {
 
   public var indexPrefixMappings: [PathPrefixMapping] { return [] }
 
+  /// Return the compiler arguments for the given source file within a target, making any necessary adjustments to
+  /// account for differences in the SwiftPM versions being linked into SwiftPM and being installed in the toolchain.
+  private func compilerArguments(for file: URL, in buildTarget: any SwiftBuildTarget) async throws -> [String] {
+    let compileArguments = try buildTarget.compileArguments(for: file)
+
+    // Fix up compiler arguments that point to a `/Modules` subdirectory if the Swift version in the toolchain is less
+    // than 6.0 because it places the modules one level higher up.
+    let toolchainVersion = await orLog("Getting Swift version") { try await toolchainRegistry.default?.swiftVersion }
+    guard let toolchainVersion, toolchainVersion < SwiftVersion(6, 0) else {
+      return compileArguments
+    }
+    return compileArguments.map { argument in
+      if argument.hasSuffix("/Modules"), argument.contains(self.workspace.location.scratchDirectory.pathString) {
+        return String(argument.dropLast(8))
+      }
+      return argument
+    }
+  }
+
   public func buildSettings(
     for uri: DocumentURI,
     in configuredTarget: ConfiguredTarget,
     language: Language
-  ) throws -> FileBuildSettings? {
+  ) async throws -> FileBuildSettings? {
     guard let url = uri.fileURL, let path = try? AbsolutePath(validating: url.path) else {
       // We can't determine build settings for non-file URIs.
       return nil
@@ -387,13 +406,13 @@ extension SwiftPMBuildSystem: SKCore.BuildSystem {
       // getting its compiler arguments and then patching up the compiler arguments by replacing the substitute file
       // with the `.cpp` file.
       return FileBuildSettings(
-        compilerArguments: try buildTarget.compileArguments(for: substituteFile),
+        compilerArguments: try await compilerArguments(for: substituteFile, in: buildTarget),
         workingDirectory: workspacePath.pathString
       ).patching(newFile: try resolveSymlinks(path).pathString, originalFile: substituteFile.absoluteString)
     }
 
     return FileBuildSettings(
-      compilerArguments: try buildTarget.compileArguments(for: url),
+      compilerArguments: try await compilerArguments(for: url, in: buildTarget),
       workingDirectory: workspacePath.pathString
     )
   }

Sources/SKTestSupport/SkipUnless.swift

@@ -170,10 +170,6 @@ public actor SkipUnless {
 
   /// SwiftPM moved the location where it stores Swift modules to a subdirectory in
   /// https://github.com/apple/swift-package-manager/pull/7103.
-  ///
-  /// sourcekit-lsp uses the built-in SwiftPM to synthesize compiler arguments and cross-module tests fail if the host
-  /// toolchain’s SwiftPM stores the Swift modules on the top level but we synthesize compiler arguments expecting the
-  /// modules to be in a `Modules` subdirectory.
   public static func swiftpmStoresModulesInSubdirectory(
     file: StaticString = #filePath,
     line: UInt = #line

Tests/SKSwiftPMWorkspaceTests/SwiftPMBuildSystemTests.swift

@@ -28,11 +28,11 @@ import struct PackageModel.BuildFlags
 #endif
 
 fileprivate extension SwiftPMBuildSystem {
-  func buildSettings(for uri: DocumentURI, language: Language) throws -> FileBuildSettings? {
+  func buildSettings(for uri: DocumentURI, language: Language) async throws -> FileBuildSettings? {
     guard let target = self.configuredTargets(for: uri).only else {
       return nil
     }
-    return try buildSettings(for: uri, in: target, language: language)
+    return try await buildSettings(for: uri, in: target, language: language)
   }
 }
 
@@ -116,6 +116,7 @@ final class SwiftPMBuildSystemTests: XCTestCase {
   }
 
   func testBasicSwiftArgs() async throws {
+    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
     let fs = localFileSystem
     try await withTestScratchDir { tempDir in
       try fs.createFiles(

Tests/SourceKitLSPTests/BackgroundIndexingTests.swift

@@ -104,7 +104,6 @@ final class BackgroundIndexingTests: XCTestCase {
   }
 
   func testBackgroundIndexingOfMultiModuleProject() async throws {
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
     let project = try await SwiftPMTestProject(
       files: [
         "LibA/MyFile.swift": """
@@ -212,7 +211,6 @@ final class BackgroundIndexingTests: XCTestCase {
   }
 
   func testBackgroundIndexingOfPackageDependency() async throws {
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
     let dependencyContents = """
       public func 1️⃣doSomething() {}
       """
@@ -541,7 +539,6 @@ final class BackgroundIndexingTests: XCTestCase {
   }
 
   func testPrepareTargetAfterEditToDependency() async throws {
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
     var serverOptions = SourceKitLSPServer.Options.testDefault
     let expectedPreparationTracker = ExpectedIndexTaskTracker(expectedPreparations: [
       [
@@ -651,7 +648,6 @@ final class BackgroundIndexingTests: XCTestCase {
     let libBStartedPreparation = self.expectation(description: "LibB started preparing")
     let libDPreparedForEditing = self.expectation(description: "LibD prepared for editing")
 
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
     var serverOptions = SourceKitLSPServer.Options.testDefault
     let expectedPreparationTracker = ExpectedIndexTaskTracker(expectedPreparations: [
       // Preparation of targets during the initial of the target
@@ -749,8 +745,6 @@ final class BackgroundIndexingTests: XCTestCase {
   }
 
   func testIndexingHappensInParallel() async throws {
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
-
     let fileAIndexingStarted = self.expectation(description: "FileA indexing started")
     let fileBIndexingStarted = self.expectation(description: "FileB indexing started")
 

Tests/SourceKitLSPTests/DefinitionTests.swift

@@ -440,7 +440,6 @@ class DefinitionTests: XCTestCase {
 
   func testDependentModuleGotBuilt() async throws {
     try SkipUnless.longTestsEnabled()
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
     let project = try await SwiftPMTestProject(
       files: [
         "LibA/LibA.swift": """

Tests/SourceKitLSPTests/DependencyTrackingTests.swift

@@ -16,7 +16,6 @@ import XCTest
 
 final class DependencyTrackingTests: XCTestCase {
   func testDependenciesUpdatedSwift() async throws {
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
     let project = try await SwiftPMTestProject(
       files: [
         "LibA/LibA.swift": """

Tests/SourceKitLSPTests/IndexTests.swift

@@ -16,7 +16,6 @@ import XCTest
 
 final class IndexTests: XCTestCase {
   func testIndexSwiftModules() async throws {
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
     let project = try await SwiftPMTestProject(
       files: [
         "LibA/LibA.swift": """

Tests/SourceKitLSPTests/PublishDiagnosticsTests.swift

@@ -154,7 +154,6 @@ final class PublishDiagnosticsTests: XCTestCase {
 
   func testDiagnosticUpdatedAfterDependentModuleIsBuilt() async throws {
     try SkipUnless.longTestsEnabled()
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
 
     let project = try await SwiftPMTestProject(
       files: [

Tests/SourceKitLSPTests/PullDiagnosticsTests.swift

@@ -185,7 +185,6 @@ final class PullDiagnosticsTests: XCTestCase {
 
   func testDiagnosticUpdatedAfterDependentModuleIsBuilt() async throws {
     try SkipUnless.longTestsEnabled()
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
 
     let project = try await SwiftPMTestProject(
       files: [
@@ -251,8 +250,6 @@ final class PullDiagnosticsTests: XCTestCase {
   }
 
   func testDiagnosticsWaitForDocumentToBePrepared() async throws {
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
-
     nonisolated(unsafe) var diagnosticRequestSent = AtomicBool(initialValue: false)
     var serverOptions = SourceKitLSPServer.Options.testDefault
     serverOptions.indexTestHooks.preparationTaskDidStart = { @Sendable taskDescription in

Tests/SourceKitLSPTests/SwiftInterfaceTests.swift

@@ -55,7 +55,6 @@ final class SwiftInterfaceTests: XCTestCase {
   }
 
   func testOpenInterface() async throws {
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
     let project = try await SwiftPMTestProject(
       files: [
         "MyLibrary/MyLibrary.swift": """
@@ -152,7 +151,6 @@ final class SwiftInterfaceTests: XCTestCase {
   }
 
   func testSwiftInterfaceAcrossModules() async throws {
-    try await SkipUnless.swiftpmStoresModulesInSubdirectory()
     let project = try await SwiftPMTestProject(
       files: [
         "MyLibrary/MyLibrary.swift": """