SwiftLanguageService.swift

//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2020 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 Dispatch
import Foundation
import IndexStoreDB
import LSPLogging
import LanguageServerProtocol
import SKCore
import SKSupport
import SemanticIndex
import SourceKitD
import SwiftParser
import SwiftParserDiagnostics
import SwiftSyntax

import struct TSCBasic.AbsolutePath

#if os(Windows)
import WinSDK
#endif

fileprivate extension Range {
  /// Checks if this range overlaps with the other range, counting an overlap with an empty range as a valid overlap.
  /// The standard library implementation makes `1..<3.overlaps(2..<2)` return false because the second range is empty and thus the overlap is also empty.
  /// This implementation over overlap considers such an inclusion of an empty range as a valid overlap.
  func overlapsIncludingEmptyRanges(other: Range<Bound>) -> Bool {
    switch (self.isEmpty, other.isEmpty) {
    case (true, true):
      return self.lowerBound == other.lowerBound
    case (true, false):
      return other.contains(self.lowerBound)
    case (false, true):
      return self.contains(other.lowerBound)
    case (false, false):
      return self.overlaps(other)
    }
  }
}

/// Explicitly blacklisted `DocumentURI` schemes.
fileprivate let excludedDocumentURISchemes: [String] = [
  "git",
  "hg",
]

/// Returns true if diagnostics should be emitted for the given document.
///
/// Some editors  (like Visual Studio Code) use non-file URLs to manage source control diff bases
/// for the active document, which can lead to duplicate diagnostics in the Problems view.
/// As a workaround we explicitly blacklist those URIs and don't emit diagnostics for them.
///
/// Additionally, as of Xcode 11.4, sourcekitd does not properly handle non-file URLs when
/// the `-working-directory` argument is passed since it incorrectly applies it to the input
/// argument but not the internal primary file, leading sourcekitd to believe that the input
/// file is missing.
fileprivate func diagnosticsEnabled(for document: DocumentURI) -> Bool {
  guard let scheme = document.scheme else { return true }
  return !excludedDocumentURISchemes.contains(scheme)
}

/// A swift compiler command derived from a `FileBuildSettingsChange`.
public struct SwiftCompileCommand: Sendable, Equatable {

  /// The compiler arguments, including working directory. This is required since sourcekitd only
  /// accepts the working directory via the compiler arguments.
  public let compilerArgs: [String]

  /// Whether the compiler arguments are considered fallback - we withhold diagnostics for
  /// fallback arguments and represent the file state differently.
  public let isFallback: Bool

  public init(_ settings: FileBuildSettings) {
    let baseArgs = settings.compilerArguments
    // Add working directory arguments if needed.
    if let workingDirectory = settings.workingDirectory, !baseArgs.contains("-working-directory") {
      self.compilerArgs = baseArgs + ["-working-directory", workingDirectory]
    } else {
      self.compilerArgs = baseArgs
    }
    self.isFallback = settings.isFallback
  }
}

public actor SwiftLanguageService: LanguageService, Sendable {
  /// The ``SourceKitLSPServer`` instance that created this `ClangLanguageService`.
  weak var sourceKitLSPServer: SourceKitLSPServer?

  let sourcekitd: SourceKitD

  /// Path to the swift-format executable if it exists in the toolchain.
  let swiftFormat: AbsolutePath?

  /// Queue on which notifications from sourcekitd are handled to ensure we are
  /// handling them in-order.
  let sourcekitdNotificationHandlingQueue = AsyncQueue<Serial>()

  let capabilityRegistry: CapabilityRegistry

  let serverOptions: SourceKitLSPServer.Options

  /// Directory where generated Swift interfaces will be stored.
  let generatedInterfacesPath: URL

  // FIXME: ideally we wouldn't need separate management from a parent server in the same process.
  var documentManager: DocumentManager

  /// For each edited document, the last task that was triggered to send a `PublishDiagnosticsNotification`.
  ///
  /// This is used to cancel previous publish diagnostics tasks if an edit is made to a document.
  ///
  /// - Note: We only clear entries from the dictionary when a document is closed. The task that the document maps to
  ///   might have finished. This isn't an issue since the tasks do not retain `self`.
  private var inFlightPublishDiagnosticsTasks: [DocumentURI: Task<Void, Never>] = [:]

  let syntaxTreeManager = SyntaxTreeManager()

  /// The `semanticIndexManager` of the workspace this language service was created for.
  private let semanticIndexManager: SemanticIndexManager?

  nonisolated var keys: sourcekitd_api_keys { return sourcekitd.keys }
  nonisolated var requests: sourcekitd_api_requests { return sourcekitd.requests }
  nonisolated var values: sourcekitd_api_values { return sourcekitd.values }

  /// When sourcekitd is crashed, a `WorkDoneProgressManager` that display the sourcekitd crash status in the client.
  private var sourcekitdCrashedWorkDoneProgress: WorkDoneProgressManager?

  private var state: LanguageServerState {
    didSet {
      for handler in stateChangeHandlers {
        handler(oldValue, state)
      }

      guard let sourceKitLSPServer else {
        sourcekitdCrashedWorkDoneProgress = nil
        return
      }
      switch state {
      case .connected:
        sourcekitdCrashedWorkDoneProgress = nil
      case .connectionInterrupted, .semanticFunctionalityDisabled:
        if sourcekitdCrashedWorkDoneProgress == nil {
          sourcekitdCrashedWorkDoneProgress = WorkDoneProgressManager(
            server: sourceKitLSPServer,
            capabilityRegistry: capabilityRegistry,
            title: "SourceKit-LSP: Restoring functionality",
            message: "Please run 'sourcekit-lsp diagnose' to file an issue"
          )
        }
      }
    }
  }

  private var stateChangeHandlers: [(_ oldState: LanguageServerState, _ newState: LanguageServerState) -> Void] = []

  private var diagnosticReportManager: DiagnosticReportManager!

  /// Calling `scheduleCall` on `refreshDiagnosticsDebouncer` schedules a `DiagnosticsRefreshRequest` to be sent to
  /// to the client.
  ///
  /// We debounce these calls because the `DiagnosticsRefreshRequest` is a workspace-wide request. If we discover that
  /// the client should update diagnostics for file A and then discover that it should also update diagnostics for file
  /// B, we don't want to send two `DiagnosticsRefreshRequest`s. Instead, the two should be unified into a single
  /// request.
  private let refreshDiagnosticsDebouncer: Debouncer<Void>

  /// Only exists to work around rdar://116221716.
  /// Once that is fixed, remove the property and make `diagnosticReportManager` non-optional.
  private var clientHasDiagnosticsCodeDescriptionSupport: Bool {
    get async {
      return await capabilityRegistry.clientHasDiagnosticsCodeDescriptionSupport
    }
  }

  /// Creates a language server for the given client using the sourcekitd dylib specified in `toolchain`.
  /// `reopenDocuments` is a closure that will be called if sourcekitd crashes and the `SwiftLanguageService` asks its
  /// parent server to reopen all of its documents.
  /// Returns `nil` if `sourcekitd` couldn't be found.
  public init?(
    sourceKitLSPServer: SourceKitLSPServer,
    toolchain: Toolchain,
    options: SourceKitLSPServer.Options,
    workspace: Workspace
  ) async throws {
    guard let sourcekitd = toolchain.sourcekitd else { return nil }
    self.sourceKitLSPServer = sourceKitLSPServer
    self.swiftFormat = toolchain.swiftFormat
    self.sourcekitd = try await DynamicallyLoadedSourceKitD.getOrCreate(dylibPath: sourcekitd)
    self.capabilityRegistry = workspace.capabilityRegistry
    self.semanticIndexManager = workspace.semanticIndexManager
    self.serverOptions = options
    self.documentManager = DocumentManager()
    self.state = .connected
    self.generatedInterfacesPath = options.generatedInterfacesPath.asURL
    try FileManager.default.createDirectory(at: generatedInterfacesPath, withIntermediateDirectories: true)
    self.diagnosticReportManager = nil  // Needed to work around rdar://116221716

    // The debounce duration of 500ms was chosen arbitrarily without scientific research.
    self.refreshDiagnosticsDebouncer = Debouncer(debounceDuration: .milliseconds(500)) { [weak sourceKitLSPServer] in
      guard let sourceKitLSPServer else {
        logger.fault("Not sending DiagnosticRefreshRequest to client because sourceKitLSPServer has been deallocated")
        return
      }
      _ = await orLog("Sending DiagnosticRefreshRequest to client after document dependencies updated") {
        try await sourceKitLSPServer.sendRequestToClient(DiagnosticsRefreshRequest())
      }
    }
    self.diagnosticReportManager = DiagnosticReportManager(
      sourcekitd: self.sourcekitd,
      syntaxTreeManager: syntaxTreeManager,
      documentManager: documentManager,
      clientHasDiagnosticsCodeDescriptionSupport: await self.clientHasDiagnosticsCodeDescriptionSupport
    )
  }

  /// - Important: For testing only
  public func setReusedNodeCallback(_ callback: (@Sendable (_ node: Syntax) -> ())?) async {
    await self.syntaxTreeManager.setReusedNodeCallback(callback)
  }

  func buildSettings(for document: DocumentURI) async -> SwiftCompileCommand? {
    guard let sourceKitLSPServer else {
      logger.fault("Cannot retrieve build settings because SourceKitLSPServer is no longer alive")
      return nil
    }
    guard let workspace = await sourceKitLSPServer.workspaceForDocument(uri: document) else {
      return nil
    }
    if let settings = await workspace.buildSystemManager.buildSettingsInferredFromMainFile(
      for: document,
      language: .swift
    ) {
      return SwiftCompileCommand(settings)
    } else {
      return nil
    }
  }

  public nonisolated func canHandle(workspace: Workspace) -> Bool {
    // We have a single sourcekitd instance for all workspaces.
    return true
  }

  public func addStateChangeHandler(
    handler: @Sendable @escaping (_ oldState: LanguageServerState, _ newState: LanguageServerState) -> Void
  ) {
    self.stateChangeHandlers.append(handler)
  }
}

extension SwiftLanguageService {

  public func initialize(_ initialize: InitializeRequest) async throws -> InitializeResult {
    await sourcekitd.addNotificationHandler(self)

    return InitializeResult(
      capabilities: ServerCapabilities(
        textDocumentSync: .options(
          TextDocumentSyncOptions(
            openClose: true,
            change: .incremental
          )
        ),
        hoverProvider: .bool(true),
        completionProvider: CompletionOptions(
          resolveProvider: false,
          triggerCharacters: [".", "("]
        ),
        definitionProvider: nil,
        implementationProvider: .bool(true),
        referencesProvider: nil,
        documentHighlightProvider: .bool(true),
        documentSymbolProvider: .bool(true),
        codeActionProvider: .value(
          CodeActionServerCapabilities(
            clientCapabilities: initialize.capabilities.textDocument?.codeAction,
            codeActionOptions: CodeActionOptions(codeActionKinds: [.quickFix, .refactor]),
            supportsCodeActions: true
          )
        ),
        colorProvider: .bool(true),
        foldingRangeProvider: .bool(true),
        executeCommandProvider: ExecuteCommandOptions(
          commands: builtinSwiftCommands
        ),
        semanticTokensProvider: SemanticTokensOptions(
          legend: SemanticTokensLegend(
            tokenTypes: SemanticTokenTypes.all.map(\.name),
            tokenModifiers: SemanticTokenModifiers.all.compactMap(\.name)
          ),
          range: .bool(true),
          full: .bool(true)
        ),
        inlayHintProvider: .value(InlayHintOptions(resolveProvider: false)),
        diagnosticProvider: DiagnosticOptions(
          interFileDependencies: true,
          workspaceDiagnostics: false
        )
      )
    )
  }

  public func clientInitialized(_: InitializedNotification) {
    // Nothing to do.
  }

  public func shutdown() async {
    await self.sourcekitd.removeNotificationHandler(self)
  }

  /// Tell sourcekitd to crash itself. For testing purposes only.
  public func _crash() async {
    let req = sourcekitd.dictionary([
      keys.request: sourcekitd.requests.crashWithExit
    ])
    _ = try? await sourcekitd.send(req, fileContents: nil)
  }

  // MARK: - Build System Integration

  private func reopenDocument(_ snapshot: DocumentSnapshot, _ compileCmd: SwiftCompileCommand?) async {
    cancelInFlightPublishDiagnosticsTask(for: snapshot.uri)
    await diagnosticReportManager.removeItemsFromCache(with: snapshot.uri)

    let closeReq = closeDocumentSourcekitdRequest(uri: snapshot.uri)
    _ = try? await self.sourcekitd.send(closeReq, fileContents: nil)

    let openReq = openDocumentSourcekitdRequest(snapshot: snapshot, compileCommand: compileCmd)
    _ = try? await self.sourcekitd.send(openReq, fileContents: snapshot.text)

    if await capabilityRegistry.clientSupportsPullDiagnostics(for: .swift) {
      await self.refreshDiagnosticsDebouncer.scheduleCall()
    } else {
      await publishDiagnosticsIfNeeded(for: snapshot.uri)
    }
  }

  public func documentUpdatedBuildSettings(_ uri: DocumentURI) async {
    // We may not have a snapshot if this is called just before `openDocument`.
    guard let snapshot = try? self.documentManager.latestSnapshot(uri) else {
      return
    }

    // Close and re-open the document internally to inform sourcekitd to update the compile
    // command. At the moment there's no better way to do this.
    await self.reopenDocument(snapshot, await self.buildSettings(for: uri))
  }

  public func documentDependenciesUpdated(_ uri: DocumentURI) async {
    await orLog("Sending dependencyUpdated request to sourcekitd") {
      let req = sourcekitd.dictionary([
        keys.request: requests.dependencyUpdated
      ])
      _ = try await self.sourcekitd.send(req, fileContents: nil)
    }
    // `documentUpdatedBuildSettings` already handles reopening the document, so we do that here as well.
    await self.documentUpdatedBuildSettings(uri)
  }

  // MARK: - Text synchronization

  private func openDocumentSourcekitdRequest(
    snapshot: DocumentSnapshot,
    compileCommand: SwiftCompileCommand?
  ) -> SKDRequestDictionary {
    return sourcekitd.dictionary([
      keys.request: self.requests.editorOpen,
      keys.name: snapshot.uri.pseudoPath,
      keys.sourceText: snapshot.text,
      keys.enableSyntaxMap: 0,
      keys.enableStructure: 0,
      keys.enableDiagnostics: 0,
      keys.syntacticOnly: 1,
      keys.compilerArgs: compileCommand?.compilerArgs as [SKDRequestValue]?,
    ])
  }

  private func closeDocumentSourcekitdRequest(uri: DocumentURI) -> SKDRequestDictionary {
    return sourcekitd.dictionary([
      keys.request: requests.editorClose,
      keys.name: uri.pseudoPath,
      keys.cancelBuilds: 0,
    ])
  }

  public func openDocument(_ notification: DidOpenTextDocumentNotification) async {
    cancelInFlightPublishDiagnosticsTask(for: notification.textDocument.uri)
    await diagnosticReportManager.removeItemsFromCache(with: notification.textDocument.uri)

    guard let snapshot = self.documentManager.open(notification) else {
      // Already logged failure.
      return
    }

    let buildSettings = await self.buildSettings(for: snapshot.uri)
    if buildSettings == nil || buildSettings!.isFallback, let fileUrl = notification.textDocument.uri.fileURL {
      // Do not show this notification for non-file URIs to make sure we don't see this notificaiton for newly created
      // files (which get opened as with a `untitled:Unitled-1` URI by VS Code.
      sourceKitLSPServer?.sendNotificationToClient(
        ShowMessageNotification(
          type: .warning,
          message: """
            Failed to get compiler arguments for \(fileUrl.lastPathComponent).
            Ensure the source file is part of a Swift package or has compiler arguments in compile_commands.json.
            Functionality will be limited.
            """
        )
      )
    }

    let req = openDocumentSourcekitdRequest(snapshot: snapshot, compileCommand: buildSettings)
    _ = try? await self.sourcekitd.send(req, fileContents: snapshot.text)
    await publishDiagnosticsIfNeeded(for: notification.textDocument.uri)
  }

  public func closeDocument(_ notification: DidCloseTextDocumentNotification) async {
    cancelInFlightPublishDiagnosticsTask(for: notification.textDocument.uri)
    inFlightPublishDiagnosticsTasks[notification.textDocument.uri] = nil
    await diagnosticReportManager.removeItemsFromCache(with: notification.textDocument.uri)

    self.documentManager.close(notification)

    let req = closeDocumentSourcekitdRequest(uri: notification.textDocument.uri)
    _ = try? await self.sourcekitd.send(req, fileContents: nil)
  }

  /// Cancels any in-flight tasks to send a `PublishedDiagnosticsNotification` after edits.
  private func cancelInFlightPublishDiagnosticsTask(for document: DocumentURI) {
    if let inFlightTask = inFlightPublishDiagnosticsTasks[document] {
      inFlightTask.cancel()
    }
  }

  /// If the client doesn't support pull diagnostics, compute diagnostics for the latest version of the given document
  /// and send a `PublishDiagnosticsNotification` to the client for it.
  private func publishDiagnosticsIfNeeded(for document: DocumentURI) async {
    await withLoggingScope("publish-diagnostics") {
      await publishDiagnosticsIfNeededImpl(for: document)
    }
  }

  private func publishDiagnosticsIfNeededImpl(for document: DocumentURI) async {
    guard await !capabilityRegistry.clientSupportsPullDiagnostics(for: .swift) else {
      return
    }
    guard diagnosticsEnabled(for: document) else {
      return
    }
    cancelInFlightPublishDiagnosticsTask(for: document)
    inFlightPublishDiagnosticsTasks[document] = Task(priority: .medium) { [weak self] in
      guard let self, let sourceKitLSPServer = await self.sourceKitLSPServer else {
        logger.fault("Cannot produce PublishDiagnosticsNotification because sourceKitLSPServer was deallocated")
        return
      }
      do {
        // Sleep for a little bit until triggering the diagnostic generation. This effectively de-bounces diagnostic
        // generation since any later edit will cancel the previous in-flight task, which will thus never go on to send
        // the `DocumentDiagnosticsRequest`.
        try await Task.sleep(
          nanoseconds: UInt64(sourceKitLSPServer.options.swiftPublishDiagnosticsDebounceDuration * 1_000_000_000)
        )
      } catch {
        return
      }
      do {
        let snapshot = try await documentManager.latestSnapshot(document)
        let buildSettings = await self.buildSettings(for: document)
        let diagnosticReport = try await self.diagnosticReportManager.diagnosticReport(
          for: snapshot,
          buildSettings: buildSettings
        )
        let latestSnapshotID = try? await documentManager.latestSnapshot(snapshot.uri).id
        if latestSnapshotID != snapshot.id {
          // Check that the document wasn't modified while we were getting diagnostics. This could happen because we are
          // calling `publishDiagnosticsIfNeeded` outside of `messageHandlingQueue` and thus a concurrent edit is
          // possible while we are waiting for the sourcekitd request to return a result.
          logger.log(
            """
            Document was modified while loading diagnostics. \
            Loaded diagnostics for \(snapshot.id.version, privacy: .public), \
            latest snapshot is \((latestSnapshotID?.version).map(String.init) ?? "<nil>", privacy: .public)
            """
          )
          throw CancellationError()
        }

        await sourceKitLSPServer.sendNotificationToClient(
          PublishDiagnosticsNotification(
            uri: document,
            diagnostics: diagnosticReport.items
          )
        )
      } catch is CancellationError {
      } catch {
        logger.fault(
          """
          Failed to get diagnostics
          \(error.forLogging)
          """
        )
      }
    }
  }

  public func changeDocument(_ notification: DidChangeTextDocumentNotification) async {
    cancelInFlightPublishDiagnosticsTask(for: notification.textDocument.uri)

    let keys = self.keys
    struct Edit {
      let offset: Int
      let length: Int
      let replacement: String
    }

    guard let (preEditSnapshot, postEditSnapshot, edits) = self.documentManager.edit(notification) else {
      return
    }

    for edit in edits {
      let req = sourcekitd.dictionary([
        keys.request: self.requests.editorReplaceText,
        keys.name: notification.textDocument.uri.pseudoPath,
        keys.enableSyntaxMap: 0,
        keys.enableStructure: 0,
        keys.enableDiagnostics: 0,
        keys.syntacticOnly: 1,
        keys.offset: edit.range.lowerBound.utf8Offset,
        keys.length: edit.range.length.utf8Length,
        keys.sourceText: edit.replacement,
      ])
      do {
        _ = try await self.sourcekitd.send(req, fileContents: nil)
      } catch {
        logger.fault(
          """
          failed to replace \(edit.range.lowerBound.utf8Offset):\(edit.range.upperBound.utf8Offset) by \
          '\(edit.replacement)' in sourcekitd
          """
        )
      }
    }

    let concurrentEdits = ConcurrentEdits(
      fromSequential: edits
    )
    await syntaxTreeManager.registerEdit(
      preEditSnapshot: preEditSnapshot,
      postEditSnapshot: postEditSnapshot,
      edits: concurrentEdits
    )

    await publishDiagnosticsIfNeeded(for: notification.textDocument.uri)
  }

  public func willSaveDocument(_ notification: WillSaveTextDocumentNotification) {

  }

  public func didSaveDocument(_ notification: DidSaveTextDocumentNotification) {

  }

  // MARK: - Language features

  public func definition(_ request: DefinitionRequest) async throws -> LocationsOrLocationLinksResponse? {
    throw ResponseError.unknown("unsupported method")
  }

  public func declaration(_ request: DeclarationRequest) async throws -> LocationsOrLocationLinksResponse? {
    throw ResponseError.unknown("unsupported method")
  }

  public func hover(_ req: HoverRequest) async throws -> HoverResponse? {
    let uri = req.textDocument.uri
    let position = req.position
    let cursorInfoResults = try await cursorInfo(uri, position..<position).cursorInfo

    let symbolDocumentations = cursorInfoResults.compactMap { (cursorInfo) -> String? in
      if let documentation = cursorInfo.documentation {
        var result = ""
        if let annotatedDeclaration = cursorInfo.annotatedDeclaration {
          let markdownDecl =
            orLog("Convert XML declaration to Markdown") {
              try xmlDocumentationToMarkdown(annotatedDeclaration)
            } ?? annotatedDeclaration
          result += "\(markdownDecl)\n"
        }
        result += documentation
        return result
      } else if let doc = cursorInfo.documentationXML {
        return """
          \(orLog("Convert XML to Markdown") { try xmlDocumentationToMarkdown(doc) } ?? doc)
          """
      } else if let annotated: String = cursorInfo.annotatedDeclaration {
        return """
          \(orLog("Convert XML to Markdown") { try xmlDocumentationToMarkdown(annotated) } ?? annotated)
          """
      } else {
        return nil
      }
    }

    if symbolDocumentations.isEmpty {
      return nil
    }

    let joinedDocumentation: String
    if let only = symbolDocumentations.only {
      joinedDocumentation = only
    } else {
      let documentationsWithSpacing = symbolDocumentations.enumerated().map { index, documentation in
        // Work around a bug in VS Code that displays a code block after a horizontal ruler without any spacing
        // (the pixels of the code block literally touch the ruler) by adding an empty line into the code block.
        // Only do this for subsequent results since only those are preceeded by a ruler.
        let prefix = "```swift\n"
        if index != 0 && documentation.starts(with: prefix) {
          return prefix + "\n" + documentation.dropFirst(prefix.count)
        } else {
          return documentation
        }
      }
      joinedDocumentation = """
        ## Multiple results

        \(documentationsWithSpacing.joined(separator: "\n\n---\n\n"))
        """
    }

    return HoverResponse(
      contents: .markupContent(MarkupContent(kind: .markdown, value: joinedDocumentation)),
      range: nil
    )
  }

  public func documentColor(_ req: DocumentColorRequest) async throws -> [ColorInformation] {
    let snapshot = try self.documentManager.latestSnapshot(req.textDocument.uri)

    let syntaxTree = await syntaxTreeManager.syntaxTree(for: snapshot)

    class ColorLiteralFinder: SyntaxVisitor {
      let snapshot: DocumentSnapshot
      var result: [ColorInformation] = []

      init(snapshot: DocumentSnapshot) {
        self.snapshot = snapshot
        super.init(viewMode: .sourceAccurate)
      }

      override func visit(_ node: MacroExpansionExprSyntax) -> SyntaxVisitorContinueKind {
        guard node.macroName.text == "colorLiteral" else {
          return .visitChildren
        }
        func extractArgument(_ argumentName: String, from arguments: LabeledExprListSyntax) -> Double? {
          for argument in arguments {
            if argument.label?.text == argumentName {
              if let integer = argument.expression.as(IntegerLiteralExprSyntax.self) {
                return Double(integer.literal.text)
              } else if let integer = argument.expression.as(FloatLiteralExprSyntax.self) {
                return Double(integer.literal.text)
              }
            }
          }
          return nil
        }
        guard let red = extractArgument("red", from: node.arguments),
          let green = extractArgument("green", from: node.arguments),
          let blue = extractArgument("blue", from: node.arguments),
          let alpha = extractArgument("alpha", from: node.arguments)
        else {
          return .skipChildren
        }

        result.append(
          ColorInformation(
            range: snapshot.absolutePositionRange(of: node.position..<node.endPosition),
            color: Color(red: red, green: green, blue: blue, alpha: alpha)
          )
        )

        return .skipChildren
      }
    }

    try Task.checkCancellation()

    let colorLiteralFinder = ColorLiteralFinder(snapshot: snapshot)
    colorLiteralFinder.walk(syntaxTree)
    return colorLiteralFinder.result
  }

  public func colorPresentation(_ req: ColorPresentationRequest) async throws -> [ColorPresentation] {
    let color = req.color
    // Empty string as a label breaks VSCode color picker
    let label = "Color Literal"
    let newText = "#colorLiteral(red: \(color.red), green: \(color.green), blue: \(color.blue), alpha: \(color.alpha))"
    let textEdit = TextEdit(range: req.range, newText: newText)
    let presentation = ColorPresentation(label: label, textEdit: textEdit, additionalTextEdits: nil)
    return [presentation]
  }

  public func documentSymbolHighlight(_ req: DocumentHighlightRequest) async throws -> [DocumentHighlight]? {
    let snapshot = try self.documentManager.latestSnapshot(req.textDocument.uri)

    let relatedIdentifiers = try await self.relatedIdentifiers(
      at: req.position,
      in: snapshot,
      includeNonEditableBaseNames: false
    )
    return relatedIdentifiers.relatedIdentifiers.map {
      DocumentHighlight(
        range: $0.range,
        kind: .read  // unknown
      )
    }
  }

  public func codeAction(_ req: CodeActionRequest) async throws -> CodeActionRequestResponse? {
    let providersAndKinds: [(provider: CodeActionProvider, kind: CodeActionKind?)] = [
      (retrieveSyntaxCodeActions, nil),
      (retrieveRefactorCodeActions, .refactor),
      (retrieveQuickFixCodeActions, .quickFix),
    ]
    let wantedActionKinds = req.context.only
    let providers: [CodeActionProvider] = providersAndKinds.compactMap {
      if let wantedActionKinds, let kind = $0.1, !wantedActionKinds.contains(kind) {
        return nil
      }

      return $0.provider
    }
    let codeActionCapabilities = capabilityRegistry.clientCapabilities.textDocument?.codeAction
    let codeActions = try await retrieveCodeActions(req, providers: providers)
    let response = CodeActionRequestResponse(
      codeActions: codeActions,
      clientCapabilities: codeActionCapabilities
    )
    return response
  }

  func retrieveCodeActions(
    _ req: CodeActionRequest,
    providers: [CodeActionProvider]
  ) async throws -> [CodeAction] {
    guard providers.isEmpty == false else {
      return []
    }
    return await providers.concurrentMap { provider in
      do {
        return try await provider(req)
      } catch {
        // Ignore any providers that failed to provide refactoring actions.
        return []
      }
    }.flatMap { $0 }.sorted { $0.title < $1.title }
  }

  func retrieveSyntaxCodeActions(_ request: CodeActionRequest) async throws -> [CodeAction] {
    let uri = request.textDocument.uri
    let snapshot = try documentManager.latestSnapshot(uri)

    let syntaxTree = await syntaxTreeManager.syntaxTree(for: snapshot)
    guard let scope = SyntaxCodeActionScope(snapshot: snapshot, syntaxTree: syntaxTree, request: request) else {
      return []
    }
    return await allSyntaxCodeActions.concurrentMap { provider in
      return provider.codeActions(in: scope)
    }.flatMap { $0 }
  }

  func retrieveRefactorCodeActions(_ params: CodeActionRequest) async throws -> [CodeAction] {
    let additionalCursorInfoParameters: ((SKDRequestDictionary) -> Void) = { skreq in
      skreq.set(self.keys.retrieveRefactorActions, to: 1)
    }

    let cursorInfoResponse = try await cursorInfo(
      params.textDocument.uri,
      params.range,
      additionalParameters: additionalCursorInfoParameters
    )

    return cursorInfoResponse.refactorActions.compactMap {
      do {
        let lspCommand = try $0.asCommand()
        return CodeAction(title: $0.title, kind: .refactor, command: lspCommand)
      } catch {
        logger.log("Failed to convert SwiftCommand to Command type: \(error.forLogging)")
        return nil
      }
    }
  }

  func retrieveQuickFixCodeActions(_ params: CodeActionRequest) async throws -> [CodeAction] {
    let snapshot = try documentManager.latestSnapshot(params.textDocument.uri)
    let buildSettings = await self.buildSettings(for: params.textDocument.uri)
    let diagnosticReport = try await self.diagnosticReportManager.diagnosticReport(
      for: snapshot,
      buildSettings: buildSettings
    )

    let codeActions = diagnosticReport.items.flatMap { (diag) -> [CodeAction] in
      let codeActions: [CodeAction] =
        (diag.codeActions ?? []) + (diag.relatedInformation?.flatMap { $0.codeActions ?? [] } ?? [])

      if codeActions.isEmpty {
        // The diagnostic doesn't have fix-its. Don't return anything.
        return []
      }

      // Check if the diagnostic overlaps with the selected range.
      guard params.range.overlapsIncludingEmptyRanges(other: diag.range) else {
        return []
      }

      // Check if the set of diagnostics provided by the request contains this diagnostic.
      // For this, only compare the 'basic' properties of the diagnostics, excluding related information and code actions since
      // code actions are only defined in an LSP extension and might not be sent back to us.
      guard
        params.context.diagnostics.contains(where: { (contextDiag) -> Bool in
          return contextDiag.range == diag.range && contextDiag.severity == diag.severity
            && contextDiag.code == diag.code && contextDiag.source == diag.source && contextDiag.message == diag.message
        })
      else {
        return []
      }

      // Flip the attachment of diagnostic to code action instead of the code action being attached to the diagnostic
      return codeActions.map({
        var codeAction = $0
        var diagnosticWithoutCodeActions = diag
        diagnosticWithoutCodeActions.codeActions = nil
        if let related = diagnosticWithoutCodeActions.relatedInformation {
          diagnosticWithoutCodeActions.relatedInformation = related.map {
            var withoutCodeActions = $0
            withoutCodeActions.codeActions = nil
            return withoutCodeActions
          }
        }
        codeAction.diagnostics = [diagnosticWithoutCodeActions]
        return codeAction
      })
    }

    return codeActions
  }

  public func inlayHint(_ req: InlayHintRequest) async throws -> [InlayHint] {
    let uri = req.textDocument.uri
    let infos = try await variableTypeInfos(uri, req.range)
    let hints = infos
      .lazy
      .filter { !$0.hasExplicitType }
      .map { info -> InlayHint in
        let position = info.range.upperBound
        let label = ": \(info.printedType)"
        let textEdits: [TextEdit]?
        if info.canBeFollowedByTypeAnnotation {
          textEdits = [TextEdit(range: position..<position, newText: label)]
        } else {
          textEdits = nil
        }
        return InlayHint(
          position: position,
          label: .string(label),
          kind: .type,
          textEdits: textEdits
        )
      }

    return Array(hints)
  }

  public func documentDiagnostic(_ req: DocumentDiagnosticsRequest) async throws -> DocumentDiagnosticReport {
    do {
      await semanticIndexManager?.prepareFileForEditorFunctionality(req.textDocument.uri)
      let snapshot = try documentManager.latestSnapshot(req.textDocument.uri)
      let buildSettings = await self.buildSettings(for: req.textDocument.uri)
      let diagnosticReport = try await self.diagnosticReportManager.diagnosticReport(
        for: snapshot,
        buildSettings: buildSettings
      )
      return .full(diagnosticReport)
    } catch {
      // VS Code does not request diagnostics again for a document if the diagnostics request failed.
      // Since sourcekit-lsp usually recovers from failures (e.g. after sourcekitd crashes), this is undesirable.
      // Instead of returning an error, return empty results.
      logger.error(
        """
        Loading diagnostic failed with the following error. Returning empty diagnostics.
        \(error.forLogging)
        """
      )
      return .full(RelatedFullDocumentDiagnosticReport(items: []))
    }
  }

  public func indexedRename(_ request: IndexedRenameRequest) async throws -> WorkspaceEdit? {
    throw ResponseError.unknown("unsupported method")
  }

  public func executeCommand(_ req: ExecuteCommandRequest) async throws -> LSPAny? {
    // TODO: If there's support for several types of commands, we might need to structure this similarly to the code actions request.
    guard let sourceKitLSPServer else {
      // `SourceKitLSPServer` has been destructed. We are tearing down the language
      // server. Nothing left to do.
      throw ResponseError.unknown("Connection to the editor closed")
    }
    guard let swiftCommand = req.swiftCommand(ofType: SemanticRefactorCommand.self) else {
      throw ResponseError.unknown("semantic refactoring: unknown command \(req.command)")
    }
    let refactor = try await semanticRefactoring(swiftCommand)
    let edit = refactor.edit
    let req = ApplyEditRequest(label: refactor.title, edit: edit)
    let response = try await sourceKitLSPServer.sendRequestToClient(req)
    if !response.applied {
      let reason: String
      if let failureReason = response.failureReason {
        reason = " reason: \(failureReason)"
      } else {
        reason = ""
      }
      logger.error("client refused to apply edit for \(refactor.title, privacy: .public)!\(reason)")
    }
    return edit.encodeToLSPAny()
  }
}

extension SwiftLanguageService: SKDNotificationHandler {
  public nonisolated func notification(_ notification: SKDResponse) {
    sourcekitdNotificationHandlingQueue.async {
      await self.notificationImpl(notification)
    }
  }

  private func notificationImpl(_ notification: SKDResponse) async {
    logger.debug(
      """
      Received notification from sourcekitd
      \(notification.forLogging)
      """
    )
    // Check if we need to update our `state` based on the contents of the notification.
    if notification.value?[self.keys.notification] == self.values.semaEnabledNotification {
      self.state = .connected
    }

    if self.state == .connectionInterrupted {
      // If we get a notification while we are restoring the connection, it means that the server has restarted.
      // We still need to wait for semantic functionality to come back up.
      self.state = .semanticFunctionalityDisabled

      // Ask our parent to re-open all of our documents.
      if let sourceKitLSPServer {
        await sourceKitLSPServer.reopenDocuments(for: self)
      } else {
        logger.fault("Cannot reopen documents because SourceKitLSPServer is no longer alive")
      }
    }

    if notification.error == .connectionInterrupted {
      self.state = .connectionInterrupted

      // We don't have any open documents anymore after sourcekitd crashed.
      // Reset the document manager to reflect that.
      self.documentManager = DocumentManager()
    }
  }
}

// MARK: - Position conversion

extension DocumentSnapshot {

  // MARK: String.Index <-> Raw UTF-8

  /// Converts the given UTF-8 offset to `String.Index`.
  ///
  /// If the offset is out-of-bounds of the snapshot, returns the closest valid index and logs a fault containing the
  /// file and line of the caller (from `callerFile` and `callerLine`).
  func indexOf(utf8Offset: Int, callerFile: StaticString = #fileID, callerLine: UInt = #line) -> String.Index {
    guard utf8Offset >= 0 else {
      logger.fault(
        """
        UTF-8 offset \(utf8Offset) is negative while converting it to String.Index \
        (\(callerFile, privacy: .public):\(callerLine, privacy: .public))
        """
      )
      return text.startIndex
    }
    guard let index = text.utf8.index(text.startIndex, offsetBy: utf8Offset, limitedBy: text.endIndex) else {
      logger.fault(
        """
        UTF-8 offset \(utf8Offset) is past end of file while converting it to String.Index \
        (\(callerFile, privacy: .public):\(callerLine, privacy: .public))
        """
      )
      return text.endIndex
    }
    return index
  }

  // MARK: Position <-> Raw UTF-8 offset

  /// Converts the given UTF-16-based line:column position to the UTF-8 offset of that position within the source file.
  ///
  /// If `position` does not refer to a valid position with in the snapshot, returns the offset of the closest valid
  /// position and logs a fault containing the file and line of the caller (from `callerFile` and `callerLine`).
  func utf8Offset(of position: Position, callerFile: StaticString = #fileID, callerLine: UInt = #line) -> Int {
    return lineTable.utf8OffsetOf(
      line: position.line,
      utf16Column: position.utf16index,
      callerFile: callerFile,
      callerLine: callerLine
    )
  }

  /// Converts the given UTF-8 offset to a UTF-16-based line:column position.
  ///
  /// If the offset is after the end of the snapshot, returns `nil` and logs a fault containing the file and line of
  /// the caller (from `callerFile` and `callerLine`).
  func positionOf(utf8Offset: Int, callerFile: StaticString = #fileID, callerLine: UInt = #line) -> Position {
    let (line, utf16Column) = lineTable.lineAndUTF16ColumnOf(
      utf8Offset: utf8Offset,
      callerFile: callerFile,
      callerLine: callerLine
    )
    return Position(line: line, utf16index: utf16Column)
  }

  /// Converts the given UTF-16 based line:column range to a UTF-8 based offset range.
  ///
  /// If the bounds of the range do not refer to a valid positions with in the snapshot, this function adjusts them to
  /// the closest valid positions and logs a fault containing the file and line of the caller (from `callerFile` and
  /// `callerLine`).
  func utf8OffsetRange(
    of range: Range<Position>,
    callerFile: StaticString = #fileID,
    callerLine: UInt = #line
  ) -> Range<Int> {
    let startOffset = utf8Offset(of: range.lowerBound, callerFile: callerFile, callerLine: callerLine)
    let endOffset = utf8Offset(of: range.upperBound, callerFile: callerFile, callerLine: callerLine)
    return startOffset..<endOffset
  }

  // MARK: Position <-> String.Index

  /// Converts the given UTF-16-based `line:column` position to a `String.Index`.
  ///
  /// If `position` does not refer to a valid position with in the snapshot, returns the index of the closest valid
  /// position and logs a fault containing the file and line of the caller (from `callerFile` and `callerLine`).
  func index(of position: Position, callerFile: StaticString = #fileID, callerLine: UInt = #line) -> String.Index {
    return lineTable.stringIndexOf(
      line: position.line,
      utf16Column: position.utf16index,
      callerFile: callerFile,
      callerLine: callerLine
    )
  }

  /// Converts the given UTF-16-based `line:column` range to a `String.Index` range.
  ///
  /// If the bounds of the range do not refer to a valid positions with in the snapshot, this function adjusts them to
  /// the closest valid positions and logs a fault containing the file and line of the caller (from `callerFile` and
  /// `callerLine`).
  func indexRange(
    of range: Range<Position>,
    callerFile: StaticString = #fileID,
    callerLine: UInt = #line
  ) -> Range<String.Index> {
    return self.index(of: range.lowerBound)..<self.index(of: range.upperBound)
  }

  /// Converts the given UTF-8 based line:column position to a UTF-16 based line-column position.
  ///
  /// If the UTF-8 based line:column pair does not refer to a valid position within the snapshot, returns the closest
  /// valid position and logs a fault containing the file and line of the caller (from `callerFile` and `callerLine`).
  func positionOf(
    zeroBasedLine: Int,
    utf8Column: Int,
    callerFile: StaticString = #fileID,
    callerLine: UInt = #line
  ) -> Position {
    let utf16Column = lineTable.utf16ColumnAt(
      line: zeroBasedLine,
      utf8Column: utf8Column,
      callerFile: callerFile,
      callerLine: callerLine
    )
    return Position(line: zeroBasedLine, utf16index: utf16Column)
  }

  // MARK: Position <-> AbsolutePosition

  /// Converts the given UTF-8-offset-based `AbsolutePosition` to a UTF-16-based line:column.
  ///
  /// If the `AbsolutePosition` out of bounds of the source file, returns the closest valid position and logs a fault
  /// containing the file and line of the caller (from `callerFile` and `callerLine`).
  func position(
    of position: AbsolutePosition,
    callerFile: StaticString = #fileID,
    callerLine: UInt = #line
  ) -> Position {
    return positionOf(utf8Offset: position.utf8Offset, callerFile: callerFile, callerLine: callerLine)
  }

  /// Converts the given UTF-16-based line:column `Position` to a UTF-8-offset-based `AbsolutePosition`.
  ///
  /// If the UTF-16 based line:column pair does not refer to a valid position within the snapshot, returns the closest
  /// valid position and logs a fault containing the file and line of the caller (from `callerFile` and `callerLine`).
  func absolutePosition(
    of position: Position,
    callerFile: StaticString = #fileID,
    callerLine: UInt = #line
  ) -> AbsolutePosition {
    let offset = utf8Offset(of: position, callerFile: callerFile, callerLine: callerLine)
    return AbsolutePosition(utf8Offset: offset)
  }

  /// Converts the lower and upper bound of the given UTF-8-offset-based `AbsolutePosition` range to a UTF-16-based
  /// line:column range for use in LSP.
  ///
  /// If the bounds of the range do not refer to a valid positions with in the snapshot, this function adjusts them to
  /// the closest valid positions and logs a fault containing the file and line of the caller (from `callerFile` and
  /// `callerLine`).
  func absolutePositionRange(
    of range: Range<AbsolutePosition>,
    callerFile: StaticString = #fileID,
    callerLine: UInt = #line
  ) -> Range<Position> {
    let lowerBound = self.position(of: range.lowerBound, callerFile: callerFile, callerLine: callerLine)
    let upperBound = self.position(of: range.upperBound, callerFile: callerFile, callerLine: callerLine)
    return lowerBound..<upperBound
  }

  /// Extracts the range of the given syntax node in terms of positions within
  /// this source file.
  func range(
    of node: some SyntaxProtocol,
    callerFile: StaticString = #fileID,
    callerLine: UInt = #line
  ) -> Range<Position> {
    let lowerBound = self.position(of: node.position, callerFile: callerFile, callerLine: callerLine)
    let upperBound = self.position(of: node.endPosition, callerFile: callerFile, callerLine: callerLine)
    return lowerBound..<upperBound
  }

  /// Converts the given UTF-16-based line:column range to a UTF-8-offset-based `ByteSourceRange`.
  ///
  /// If the bounds of the range do not refer to a valid positions with in the snapshot, this function adjusts them to
  /// the closest valid positions and logs a fault containing the file and line of the caller (from `callerFile` and
  /// `callerLine`).
  func byteSourceRange(
    of range: Range<Position>,
    callerFile: StaticString = #fileID,
    callerLine: UInt = #line
  ) -> Range<AbsolutePosition> {
    let utf8OffsetRange = utf8OffsetRange(of: range, callerFile: callerFile, callerLine: callerLine)
    return Range<AbsolutePosition>(
      position: AbsolutePosition(utf8Offset: utf8OffsetRange.startIndex),
      length: SourceLength(utf8Length: utf8OffsetRange.count)
    )
  }

  // MARK: Position <-> RenameLocation

  /// Converts the given UTF-8-based line:column `RenamedLocation` to a UTF-16-based line:column `Position`.
  ///
  /// If the UTF-8 based line:column pair does not refer to a valid position within the snapshot, returns the closest
  /// valid position and logs a fault containing the file and line of the caller (from `callerFile` and `callerLine`).
  func position(
    of renameLocation: RenameLocation,
    callerFile: StaticString = #fileID,
    callerLine: UInt = #line
  ) -> Position {
    return positionOf(
      zeroBasedLine: renameLocation.line - 1,
      utf8Column: renameLocation.utf8Column - 1,
      callerFile: callerFile,
      callerLine: callerLine
    )
  }

  // MAR: Position <-> SymbolLocation

  /// Converts the given UTF-8-offset-based `SymbolLocation` to a UTF-16-based line:column `Position`.
  ///
  /// If the UTF-8 offset is out-of-bounds of the snapshot, returns the closest valid position and logs a fault
  /// containing the file and line of the caller (from `callerFile` and `callerLine`).
  func position(
    of symbolLocation: SymbolLocation,
    callerFile: StaticString = #fileID,
    callerLine: UInt = #line
  ) -> Position {
    return positionOf(
      zeroBasedLine: symbolLocation.line - 1,
      utf8Column: symbolLocation.utf8Column - 1,
      callerFile: callerFile,
      callerLine: callerLine
    )
  }

  // MARK: AbsolutePosition <-> RenameLocation

  /// Converts the given UTF-8-based line:column `RenamedLocation` to a UTF-8-offset-based `AbsolutePosition`.
  ///
  /// If the UTF-8 based line:column pair does not refer to a valid position within the snapshot, returns the offset of
  /// the closest valid position and logs a fault containing the file and line of the caller (from `callerFile` and
  /// `callerLine`).
  func absolutePosition(
    of renameLocation: RenameLocation,
    callerFile: StaticString = #fileID,
    callerLine: UInt = #line
  ) -> AbsolutePosition {
    let utf8Offset = lineTable.utf8OffsetOf(
      line: renameLocation.line - 1,
      utf8Column: renameLocation.utf8Column - 1,
      callerFile: callerFile,
      callerLine: callerLine
    )
    return AbsolutePosition(utf8Offset: utf8Offset)
  }
}

extension sourcekitd_api_uid_t {
  func isCommentKind(_ vals: sourcekitd_api_values) -> Bool {
    switch self {
    case vals.comment, vals.commentMarker, vals.commentURL:
      return true
    default:
      return isDocCommentKind(vals)
    }
  }

  func isDocCommentKind(_ vals: sourcekitd_api_values) -> Bool {
    return self == vals.docComment || self == vals.docCommentField
  }

  func asCompletionItemKind(_ vals: sourcekitd_api_values) -> CompletionItemKind? {
    switch self {
    case vals.completionKindKeyword:
      return .keyword
    case vals.declModule:
      return .module
    case vals.declClass:
      return .class
    case vals.declStruct:
      return .struct
    case vals.declEnum:
      return .enum
    case vals.declEnumElement:
      return .enumMember
    case vals.declProtocol:
      return .interface
    case vals.declAssociatedType:
      return .typeParameter
    case vals.declTypeAlias:
      return .typeParameter  // FIXME: is there a better choice?
    case vals.declGenericTypeParam:
      return .typeParameter
    case vals.declConstructor:
      return .constructor
    case vals.declDestructor:
      return .value  // FIXME: is there a better choice?
    case vals.declSubscript:
      return .method  // FIXME: is there a better choice?
    case vals.declMethodStatic:
      return .method
    case vals.declMethodInstance:
      return .method
    case vals.declFunctionPrefixOperator,
      vals.declFunctionPostfixOperator,
      vals.declFunctionInfixOperator:
      return .operator
    case vals.declPrecedenceGroup:
      return .value
    case vals.declFunctionFree:
      return .function
    case vals.declVarStatic, vals.declVarClass:
      return .property
    case vals.declVarInstance:
      return .property
    case vals.declVarLocal,
      vals.declVarGlobal,
      vals.declVarParam:
      return .variable
    default:
      return nil
    }
  }

  func asSymbolKind(_ vals: sourcekitd_api_values) -> SymbolKind? {
    switch self {
    case vals.declClass, vals.refClass, vals.declActor, vals.refActor:
      return .class
    case vals.declMethodInstance, vals.refMethodInstance,
      vals.declMethodStatic, vals.refMethodStatic,
      vals.declMethodClass, vals.refMethodClass:
      return .method
    case vals.declVarInstance, vals.refVarInstance,
      vals.declVarStatic, vals.refVarStatic,
      vals.declVarClass, vals.refVarClass:
      return .property
    case vals.declEnum, vals.refEnum:
      return .enum
    case vals.declEnumElement, vals.refEnumElement:
      return .enumMember
    case vals.declProtocol, vals.refProtocol:
      return .interface
    case vals.declFunctionFree, vals.refFunctionFree:
      return .function
    case vals.declVarGlobal, vals.refVarGlobal,
      vals.declVarLocal, vals.refVarLocal:
      return .variable
    case vals.declStruct, vals.refStruct:
      return .struct
    case vals.declGenericTypeParam, vals.refGenericTypeParam:
      return .typeParameter
    case vals.declExtension:
      // There are no extensions in LSP, so we return something vaguely similar
      return .namespace
    case vals.refModule:
      return .module
    case vals.declConstructor, vals.refConstructor:
      return .constructor
    default:
      return nil
    }
  }
}