Allow configuring workspace type via flag

Sources/LanguageServerProtocol/SupportTypes/WorkspaceFolder.swift

@@ -18,13 +18,23 @@ public enum BuildConfiguration: Hashable, Codable {
   case release
 }
 
+/// The type of workspace; default workspace type selection logic can be overridden.
+///
+/// **(LSP Extension)**
+public enum WorkspaceType: Hashable, Codable {
+  case buildServer, compilationDatabase, swiftPM
+}
+
 /// Build settings that should be used for a workspace.
 ///
 /// **(LSP Extension)**
 public struct WorkspaceBuildSetup: Hashable, Codable {
   /// The configuration that the workspace should be built in.
   public let buildConfiguration: BuildConfiguration?
 
+  /// The default workspace type to use for this workspace.
+  public let defaultWorkspaceType: WorkspaceType?
+
   /// The build directory for the workspace.
   public let scratchPath: DocumentURI?
 
@@ -42,13 +52,15 @@ public struct WorkspaceBuildSetup: Hashable, Codable {
 
   public init(
     buildConfiguration: BuildConfiguration? = nil,
+    defaultWorkspaceType: WorkspaceType? = nil,
     scratchPath: DocumentURI? = nil,
     cFlags: [String]? = nil,
     cxxFlags: [String]? = nil,
     linkerFlags: [String]? = nil,
     swiftFlags: [String]? = nil
   ) {
     self.buildConfiguration = buildConfiguration
+    self.defaultWorkspaceType = defaultWorkspaceType
     self.scratchPath = scratchPath
     self.cFlags = cFlags
     self.cxxFlags = cxxFlags

Sources/SKCore/BuildSetup.swift

@@ -21,21 +21,31 @@ public struct BuildSetup {
   /// Default configuration
   public static let `default` = BuildSetup(
     configuration: nil,
+    defaultWorkspaceType: nil,
     path: nil,
     flags: BuildFlags()
   )
 
   /// Build configuration (debug|release).
   public var configuration: BuildConfiguration?
 
+  /// Default workspace type (buildserver|compdb|swiftpm). Overrides workspace type selection logic.
+  public var defaultWorkspaceType: WorkspaceType?
+
   /// Build artifacts directory path. If nil, the build system may choose a default value.
   public var path: AbsolutePath?
 
   /// Additional build flags
   public var flags: BuildFlags
 
-  public init(configuration: BuildConfiguration?, path: AbsolutePath?, flags: BuildFlags) {
+  public init(
+    configuration: BuildConfiguration?,
+    defaultWorkspaceType: WorkspaceType?,
+    path: AbsolutePath?,
+    flags: BuildFlags
+  ) {
     self.configuration = configuration
+    self.defaultWorkspaceType = defaultWorkspaceType
     self.path = path
     self.flags = flags
   }
@@ -49,6 +59,7 @@ public struct BuildSetup {
     flags = flags.merging(other.flags)
     return BuildSetup(
       configuration: other.configuration ?? self.configuration,
+      defaultWorkspaceType: other.defaultWorkspaceType ?? self.defaultWorkspaceType,
       path: other.path ?? self.path,
       flags: flags
     )

Sources/SKSupport/CMakeLists.txt

@@ -12,6 +12,7 @@ add_library(SKSupport STATIC
   Random.swift
   Result.swift
   ThreadSafeBox.swift
+  WorkspaceType.swift
 )
 set_target_properties(SKSupport PROPERTIES
   INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_Swift_MODULE_DIRECTORY})

Sources/SKSupport/WorkspaceType.swift

@@ -0,0 +1,17 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+public enum WorkspaceType: String {
+  case buildServer
+  case compilationDatabase
+  case swiftPM
+}

Sources/SourceKitLSP/SourceKitServer.swift

@@ -974,6 +974,17 @@ extension LanguageServerProtocol.BuildConfiguration {
   }
 }
 
+private extension LanguageServerProtocol.WorkspaceType {
+  /// Convert `LanguageServerProtocol.WorkspaceType` to `SkSupport.WorkspaceType`.
+  var workspaceType: SKSupport.WorkspaceType {
+    switch self {
+    case .buildServer: return .buildServer
+    case .compilationDatabase: return .compilationDatabase
+    case .swiftPM: return .swiftPM
+    }
+  }
+}
+
 // MARK: - Request and notification handling
 
 extension SourceKitServer {
@@ -991,6 +1002,7 @@ extension SourceKitServer {
     }
     return SKCore.BuildSetup(
       configuration: buildParams?.buildConfiguration?.configuration,
+      defaultWorkspaceType: buildParams?.defaultWorkspaceType?.workspaceType,
       path: scratchPath,
       flags: BuildFlags(
         cCompilerFlags: buildParams?.cFlags ?? [],

Sources/SourceKitLSP/Workspace.swift

@@ -108,20 +108,42 @@ public final class Workspace {
     reloadPackageStatusCallback: @escaping (ReloadPackageStatus) async -> Void
   ) async throws {
     var buildSystem: BuildSystem? = nil
-    if let rootUrl = rootUri.fileURL, let rootPath = try? AbsolutePath(validating: rootUrl.path) {
-      if let buildServer = await BuildServerBuildSystem(projectRoot: rootPath, buildSetup: buildSetup) {
-        buildSystem = buildServer
-      } else if let swiftpm = await SwiftPMWorkspace(
+
+    func buildSwiftPMWorkspace(rootUrl: URL) async -> SwiftPMWorkspace? {
+      return await SwiftPMWorkspace(
         url: rootUrl,
         toolchainRegistry: toolchainRegistry,
         buildSetup: buildSetup,
         reloadPackageStatusCallback: reloadPackageStatusCallback
-      ) {
-        buildSystem = swiftpm
-      } else if let compdb = CompilationDatabaseBuildSystem(
+      )
+    }
+
+    func buildCompDBWorkspace(rootPath: AbsolutePath) -> CompilationDatabaseBuildSystem? {
+      return CompilationDatabaseBuildSystem(
         projectRoot: rootPath,
         searchPaths: compilationDatabaseSearchPaths
-      ) {
+      )
+    }
+
+    func buildBuildServerWorkspace(rootPath: AbsolutePath) async -> BuildServerBuildSystem? {
+      return await BuildServerBuildSystem(projectRoot: rootPath, buildSetup: buildSetup)
+    }
+
+    if let rootUrl = rootUri.fileURL, let rootPath = try? AbsolutePath(validating: rootUrl.path) {
+      let defaultBuildSystem: BuildSystem? =
+        switch buildSetup.defaultWorkspaceType {
+        case .buildServer: await buildBuildServerWorkspace(rootPath: rootPath)
+        case .compilationDatabase: buildCompDBWorkspace(rootPath: rootPath)
+        case .swiftPM: await buildSwiftPMWorkspace(rootUrl: rootUrl)
+        case nil: nil
+        }
+      if let defaultBuildSystem {
+        buildSystem = defaultBuildSystem
+      } else if let buildServer = await buildBuildServerWorkspace(rootPath: rootPath) {
+        buildSystem = buildServer
+      } else if let swiftpm = await buildSwiftPMWorkspace(rootUrl: rootUrl) {
+        buildSystem = swiftpm
+      } else if let compdb = buildCompDBWorkspace(rootPath: rootPath) {
         buildSystem = compdb
       } else {
         logger.error(

Sources/sourcekit-lsp/SourceKitLSP.swift

@@ -92,6 +92,12 @@ extension SKSupport.BuildConfiguration: ExpressibleByArgument {}
 extension SKSupport.BuildConfiguration: @retroactive ExpressibleByArgument {}
 #endif
 
+#if swift(<5.10)
+extension SKSupport.WorkspaceType: ExpressibleByArgument {}
+#else
+extension SKSupport.WorkspaceType: @retroactive ExpressibleByArgument {}
+#endif
+
 @main
 struct SourceKitLSP: ParsableCommand {
   static let configuration = CommandConfiguration(
@@ -169,6 +175,11 @@ struct SourceKitLSP: ParsableCommand {
   )
   var indexPrefixMappings = [PathPrefixMapping]()
 
+  @Option(
+    help: "Override default workspace type selection; one of 'swiftPM', 'compilationDatabase', or 'buildServer'"
+  )
+  var defaultWorkspaceType: SKSupport.WorkspaceType?
+
   @Option(
     name: .customLong("compilation-db-search-path"),
     parsing: .singleValue,
@@ -191,6 +202,7 @@ struct SourceKitLSP: ParsableCommand {
     var serverOptions = SourceKitServer.Options()
 
     serverOptions.buildSetup.configuration = buildConfiguration
+    serverOptions.buildSetup.defaultWorkspaceType = defaultWorkspaceType
     serverOptions.buildSetup.path = scratchPath
     serverOptions.buildSetup.flags.cCompilerFlags = buildFlagsCc
     serverOptions.buildSetup.flags.cxxCompilerFlags = buildFlagsCxx

Tests/SKCoreTests/FallbackBuildSystemTests.swift

@@ -58,6 +58,7 @@ final class FallbackBuildSystemTests: XCTestCase {
 
     let buildSetup = BuildSetup(
       configuration: .debug,
+      defaultWorkspaceType: nil,
       path: nil,
       flags: BuildFlags(swiftCompilerFlags: [
         "-Xfrontend",
@@ -97,6 +98,7 @@ final class FallbackBuildSystemTests: XCTestCase {
 
     let buildSetup = BuildSetup(
       configuration: .debug,
+      defaultWorkspaceType: nil,
       path: nil,
       flags: BuildFlags(swiftCompilerFlags: [
         "-sdk",
@@ -169,6 +171,7 @@ final class FallbackBuildSystemTests: XCTestCase {
 
     let buildSetup = BuildSetup(
       configuration: .debug,
+      defaultWorkspaceType: nil,
       path: nil,
       flags: BuildFlags(cxxCompilerFlags: [
         "-v"
@@ -204,6 +207,7 @@ final class FallbackBuildSystemTests: XCTestCase {
 
     let buildSetup = BuildSetup(
       configuration: .debug,
+      defaultWorkspaceType: nil,
       path: nil,
       flags: BuildFlags(cxxCompilerFlags: [
         "-isysroot",
@@ -254,6 +258,7 @@ final class FallbackBuildSystemTests: XCTestCase {
 
     let buildSetup = BuildSetup(
       configuration: .debug,
+      defaultWorkspaceType: nil,
       path: nil,
       flags: BuildFlags(cCompilerFlags: [
         "-v"

Tests/SKSwiftPMWorkspaceTests/SwiftPMWorkspaceTests.swift

@@ -186,6 +186,7 @@ final class SwiftPMWorkspaceTests: XCTestCase {
 
       let config = BuildSetup(
         configuration: .release,
+        defaultWorkspaceType: nil,
         path: packageRoot.appending(component: "non_default_build_path"),
         flags: BuildFlags(cCompilerFlags: ["-m32"], swiftCompilerFlags: ["-typecheck"])
       )