Add a new test project type that uses a custom build server

This allows us to more easily test behavior for build servers that have different behavior than SwiftPM and compile commands without having to implement the build server in Python.

Author: ahoppen

Sources/BuildSystemIntegration/BuildSystemManager.swift

@@ -179,9 +179,9 @@ private extension BuildSystemSpec {
     _ createBuildSystem: @Sendable (_ connectionToSourceKitLSP: any Connection) async throws -> BuiltInBuildSystem?
   ) async -> BuildSystemAdapter? {
     let connectionToSourceKitLSP = LocalConnection(
-      receiverName: "BuildSystemManager for \(projectRoot.lastPathComponent)"
+      receiverName: "BuildSystemManager for \(projectRoot.lastPathComponent)",
+      handler: messagesToSourceKitLSPHandler
     )
-    connectionToSourceKitLSP.start(handler: messagesToSourceKitLSPHandler)
 
     let buildSystem = await orLog("Creating build system") {
       try await createBuildSystem(connectionToSourceKitLSP)
@@ -197,9 +197,9 @@ private extension BuildSystemSpec {
       buildSystemHooks: buildSystemHooks
     )
     let connectionToBuildSystem = LocalConnection(
-      receiverName: "\(type(of: buildSystem)) for \(projectRoot.lastPathComponent)"
+      receiverName: "\(type(of: buildSystem)) for \(projectRoot.lastPathComponent)",
+      handler: buildSystemAdapter
     )
-    connectionToBuildSystem.start(handler: buildSystemAdapter)
     return .builtIn(buildSystemAdapter, connectionToBuildSystem: connectionToBuildSystem)
   }
 
@@ -266,9 +266,9 @@ private extension BuildSystemSpec {
       #endif
     case .injected(let injector):
       let connectionToSourceKitLSP = LocalConnection(
-        receiverName: "BuildSystemManager for \(projectRoot.lastPathComponent)"
+        receiverName: "BuildSystemManager for \(projectRoot.lastPathComponent)",
+        handler: messagesToSourceKitLSPHandler
       )
-      connectionToSourceKitLSP.start(handler: messagesToSourceKitLSPHandler)
       return .injected(
         await injector(projectRoot, connectionToSourceKitLSP)
       )
@@ -510,8 +510,7 @@ package actor BuildSystemManager: QueueBasedMessageHandler {
           connectionToSourceKitLSP: legacyBuildServer.connectionToSourceKitLSP,
           buildSystemHooks: buildSystemHooks
         )
-        let connectionToBuildSystem = LocalConnection(receiverName: "Legacy BSP server")
-        connectionToBuildSystem.start(handler: adapter)
+        let connectionToBuildSystem = LocalConnection(receiverName: "Legacy BSP server", handler: adapter)
         self.buildSystemAdapter = .builtIn(adapter, connectionToBuildSystem: connectionToBuildSystem)
       }
       Task {

Sources/BuildSystemIntegration/CMakeLists.txt

@@ -19,8 +19,7 @@ add_library(BuildSystemIntegration STATIC
   LegacyBuildServerBuildSystem.swift
   MainFilesProvider.swift
   SplitShellCommand.swift
-  SwiftPMBuildSystem.swift
-  TestBuildSystem.swift)
+  SwiftPMBuildSystem.swift)
 set_target_properties(BuildSystemIntegration PROPERTIES
   INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_Swift_MODULE_DIRECTORY})
 target_link_libraries(BuildSystemIntegration PUBLIC

Sources/BuildSystemIntegration/LegacyBuildServerBuildSystem.swift

@@ -73,8 +73,10 @@ actor LegacyBuildServerBuildSystem: MessageHandler, BuiltInBuildSystem {
     self.configPath = configPath
     self.indexDatabasePath = nil
     self.indexStorePath = nil
-    self.connectionToSourceKitLSP = LocalConnection(receiverName: "BuildSystemManager")
-    await self.connectionToSourceKitLSP.start(handler: externalBuildSystemAdapter.messagesToSourceKitLSPHandler)
+    self.connectionToSourceKitLSP = LocalConnection(
+      receiverName: "BuildSystemManager",
+      handler: await externalBuildSystemAdapter.messagesToSourceKitLSPHandler
+    )
     await externalBuildSystemAdapter.changeMessageToSourceKitLSPHandler(to: self)
     self.buildServer = await externalBuildSystemAdapter.connectionToBuildServer
   }

Sources/LanguageServerProtocolExtensions/LocalConnection.swift

@@ -56,6 +56,11 @@ package final class LocalConnection: Connection, Sendable {
     self.name = receiverName
   }
 
+  package convenience init(receiverName: String, handler: MessageHandler) {
+    self.init(receiverName: receiverName)
+    self.start(handler: handler)
+  }
+
   deinit {
     queue.sync {
       if state != .closed {

Sources/BuildSystemIntegration/TestBuildSystem.swift renamed to Sources/SKTestSupport/CustomBuildServerTestProject.swift

@@ -2,53 +2,61 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 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 Foundation
+import BuildSystemIntegration
 import LanguageServerProtocolExtensions
 import SKLogging
-import SKOptions
+import SourceKitLSP
+import SwiftExtensions
 import ToolchainRegistry
+import XCTest
 
 #if compiler(>=6)
 package import BuildServerProtocol
+package import Foundation
 package import LanguageServerProtocol
+package import SKOptions
 #else
 import BuildServerProtocol
+import Foundation
 import LanguageServerProtocol
+import SKOptions
 #endif
 
-/// Build system to be used for testing BuildSystem and BuildSystemDelegate functionality with SourceKitLSPServer
-/// and other components.
-package actor TestBuildSystem: MessageHandler {
-  private let connectionToSourceKitLSP: any Connection
-
-  /// Build settings by file.
-  private var buildSettingsByFile: [DocumentURI: TextDocumentSourceKitOptionsResponse] = [:]
-
-  package func setBuildSettings(for uri: DocumentURI, to buildSettings: TextDocumentSourceKitOptionsResponse?) {
-    buildSettingsByFile[uri] = buildSettings
-    connectionToSourceKitLSP.send(OnBuildTargetDidChangeNotification(changes: nil))
-  }
+// MARK: - CustomBuildServer
 
-  private let initializeData: SourceKitInitializeBuildResponseData
+/// A build server that can be injected into `CustomBuildServerTestProject`.
+package protocol CustomBuildServer: MessageHandler {
+  init(projectRoot: URL, connectionToSourceKitLSP: any Connection)
 
-  package init(
-    initializeData: SourceKitInitializeBuildResponseData = SourceKitInitializeBuildResponseData(
-      sourceKitOptionsProvider: true
-    ),
-    connectionToSourceKitLSP: any Connection
-  ) {
-    self.initializeData = initializeData
-    self.connectionToSourceKitLSP = connectionToSourceKitLSP
-  }
+  func initializeBuildRequest(_ request: InitializeBuildRequest) async throws -> InitializeBuildResponse
+  func onBuildInitialized(_ notification: OnBuildInitializedNotification) throws
+  func buildShutdown(_ request: BuildShutdownRequest) async throws -> VoidResponse
+  func onBuildExit(_ notification: OnBuildExitNotification) throws
+  func workspaceBuildTargetsRequest(
+    _ request: WorkspaceBuildTargetsRequest
+  ) async throws -> WorkspaceBuildTargetsResponse
+  func buildTargetSourcesRequest(_ request: BuildTargetSourcesRequest) async throws -> BuildTargetSourcesResponse
+  func textDocumentSourceKitOptionsRequest(
+    _ request: TextDocumentSourceKitOptionsRequest
+  ) async throws -> TextDocumentSourceKitOptionsResponse?
+  func prepareTarget(_ request: BuildTargetPrepareRequest) async throws -> VoidResponse
+  func waitForBuildSystemUpdates(request: WorkspaceWaitForBuildSystemUpdatesRequest) async -> VoidResponse
+  nonisolated func onWatchedFilesDidChange(_ notification: OnWatchedFilesDidChangeNotification) throws
+  func workspaceWaitForBuildSystemUpdatesRequest(
+    _ request: WorkspaceWaitForBuildSystemUpdatesRequest
+  ) async throws -> VoidResponse
+  nonisolated func cancelRequest(_ notification: CancelRequestNotification) throws
+}
 
+extension CustomBuildServer {
   package nonisolated func handle(_ notification: some NotificationType) {
     do {
       switch notification {
@@ -64,7 +72,7 @@ package actor TestBuildSystem: MessageHandler {
         throw ResponseError.methodNotFound(type(of: notification).method)
       }
     } catch {
-      logger.error("Error while handling BSP notification")
+      logger.error("Error while handling BSP notification: \(error.forLogging)")
     }
   }
 
@@ -102,10 +110,18 @@ package actor TestBuildSystem: MessageHandler {
       reply(.failure(ResponseError.methodNotFound(type(of: request).method)))
     }
   }
+}
 
-  func initializeBuildRequest(_ request: InitializeBuildRequest) async throws -> InitializeBuildResponse {
-    return InitializeBuildResponse(
-      displayName: "TestBuildSystem",
+package extension CustomBuildServer {
+  // MARK: Helper functions for the implementation of BSP methods
+
+  func initializationResponse(
+    initializeData: SourceKitInitializeBuildResponseData = SourceKitInitializeBuildResponseData(
+      sourceKitOptionsProvider: true
+    )
+  ) -> InitializeBuildResponse {
+    InitializeBuildResponse(
+      displayName: "\(type(of: self))",
       version: "",
       bspVersion: "2.2.0",
       capabilities: BuildServerCapabilities(),
@@ -114,17 +130,25 @@ package actor TestBuildSystem: MessageHandler {
     )
   }
 
-  nonisolated func onBuildInitialized(_ notification: OnBuildInitializedNotification) throws {
-    // Nothing to do
+  func dummyTargetSourcesResponse(_ files: some Sequence<DocumentURI>) -> BuildTargetSourcesResponse {
+    return BuildTargetSourcesResponse(items: [
+      SourcesItem(target: .dummy, sources: files.map { SourceItem(uri: $0, kind: .file, generated: false) })
+    ])
   }
 
+  // MARK: Default implementation for all build server methods that usually don't need customization.
+
+  func initializeBuildRequest(_ request: InitializeBuildRequest) async throws -> InitializeBuildResponse {
+    return initializationResponse()
+  }
+
+  nonisolated func onBuildInitialized(_ notification: OnBuildInitializedNotification) throws {}
+
   func buildShutdown(_ request: BuildShutdownRequest) async throws -> VoidResponse {
     return VoidResponse()
   }
 
-  nonisolated func onBuildExit(_ notification: OnBuildExitNotification) throws {
-    // Nothing to do
-  }
+  nonisolated func onBuildExit(_ notification: OnBuildExitNotification) throws {}
 
   func workspaceBuildTargetsRequest(
     _ request: WorkspaceBuildTargetsRequest
@@ -142,32 +166,15 @@ package actor TestBuildSystem: MessageHandler {
     ])
   }
 
-  func buildTargetSourcesRequest(_ request: BuildTargetSourcesRequest) async throws -> BuildTargetSourcesResponse {
-    return BuildTargetSourcesResponse(items: [
-      SourcesItem(
-        target: .dummy,
-        sources: buildSettingsByFile.keys.map { SourceItem(uri: $0, kind: .file, generated: false) }
-      )
-    ])
-  }
-
-  func textDocumentSourceKitOptionsRequest(
-    _ request: TextDocumentSourceKitOptionsRequest
-  ) async throws -> TextDocumentSourceKitOptionsResponse? {
-    return buildSettingsByFile[request.textDocument.uri]
-  }
-
   func prepareTarget(_ request: BuildTargetPrepareRequest) async throws -> VoidResponse {
     return VoidResponse()
   }
 
-  package func waitForBuildSystemUpdates(request: WorkspaceWaitForBuildSystemUpdatesRequest) async -> VoidResponse {
+  func waitForBuildSystemUpdates(request: WorkspaceWaitForBuildSystemUpdatesRequest) async -> VoidResponse {
     return VoidResponse()
   }
 
-  nonisolated func onWatchedFilesDidChange(_ notification: OnWatchedFilesDidChangeNotification) throws {
-    // Not watching any files
-  }
+  nonisolated func onWatchedFilesDidChange(_ notification: OnWatchedFilesDidChangeNotification) throws {}
 
   func workspaceWaitForBuildSystemUpdatesRequest(
     _ request: WorkspaceWaitForBuildSystemUpdatesRequest
@@ -177,3 +184,40 @@ package actor TestBuildSystem: MessageHandler {
 
   nonisolated func cancelRequest(_ notification: CancelRequestNotification) throws {}
 }
+
+// MARK: - CustomBuildServerTestProject
+
+/// A test project that launches a custom build server in-process.
+///
+/// In contrast to `ExternalBuildServerTestProject`, the custom build system runs in-process and is implemented in
+/// Swift.
+package final class CustomBuildServerTestProject<BuildServer: CustomBuildServer>: MultiFileTestProject {
+  private let buildServerBox = ThreadSafeBox<BuildServer?>(initialValue: nil)
+
+  package init(
+    files: [RelativeFileLocation: String],
+    buildServer buildServerType: BuildServer.Type,
+    options: SourceKitLSPOptions? = nil,
+    enableBackgroundIndexing: Bool = false,
+    testName: String = #function
+  ) async throws {
+    let hooks: Hooks = Hooks(
+      buildSystemHooks: BuildSystemHooks(injectBuildServer: { [buildServerBox] projectRoot, connectionToSourceKitLSP in
+        let buildServer = BuildServer(projectRoot: projectRoot, connectionToSourceKitLSP: connectionToSourceKitLSP)
+        buildServerBox.value = buildServer
+        return LocalConnection(receiverName: "TestBuildSystem", handler: buildServer)
+      })
+    )
+    try await super.init(
+      files: files,
+      options: options,
+      hooks: hooks,
+      enableBackgroundIndexing: enableBackgroundIndexing,
+      testName: testName
+    )
+  }
+
+  package func buildServer(file: StaticString = #filePath, line: UInt = #line) throws -> BuildServer {
+    try XCTUnwrap(buildServerBox.value, "Accessing build server before it has been created", file: file, line: line)
+  }
+}

Sources/SKTestSupport/BuildServerTestProject.swift renamed to Sources/SKTestSupport/ExternalBuildServerTestProject.swift

@@ -59,7 +59,7 @@ private let skTestSupportInputsDirectory: URL = {
 ///
 /// The build server can contain `$SDK_ARGS`, which will replaced by `"-sdk", "/path/to/sdk"` on macOS and by an empty
 /// string on all other platforms.
-package class BuildServerTestProject: MultiFileTestProject {
+package class ExternalBuildServerTestProject: MultiFileTestProject {
   package init(
     files: [RelativeFileLocation: String],
     buildServerConfigLocation: RelativeFileLocation = ".bsp/sourcekit-lsp.json",