Add Show Objective-C Selector code action

Sources/SourceKitD/sourcekitd_uids.swift

@@ -878,6 +878,8 @@ package struct sourcekitd_api_requests {
   package let findLocalRenameRanges: sourcekitd_api_uid_t
   /// `source.request.semantic.refactoring`
   package let semanticRefactoring: sourcekitd_api_uid_t
+  /// `source.request.objc.selector`
+  package let objcSelector: sourcekitd_api_uid_t
   /// `source.request.enable-compile-notifications`
   package let enableCompileNotifications: sourcekitd_api_uid_t
   /// `source.request.test_notification`
@@ -951,6 +953,7 @@ package struct sourcekitd_api_requests {
     findRenameRanges = api.uid_get_from_cstr("source.request.find-syntactic-rename-ranges")!
     findLocalRenameRanges = api.uid_get_from_cstr("source.request.find-local-rename-ranges")!
     semanticRefactoring = api.uid_get_from_cstr("source.request.semantic.refactoring")!
+    objcSelector = api.uid_get_from_cstr("source.request.objc.selector")!
     enableCompileNotifications = api.uid_get_from_cstr("source.request.enable-compile-notifications")!
     testNotification = api.uid_get_from_cstr("source.request.test_notification")!
     collectExpressionType = api.uid_get_from_cstr("source.request.expression.type")!

Sources/SwiftLanguageService/ShowObjCSelector.swift

@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// 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
+@_spi(SourceKitLSP) import LanguageServerProtocol
+@_spi(SourceKitLSP) import SKLogging
+import SourceKitD
+import SourceKitLSP
+
+extension SwiftLanguageService {
+  /// Gets the Objective-C selector for the method at the given position.
+  ///
+  /// Uses the `source.request.objc.selector` sourcekitd request directly
+  /// to retrieve the selector string for @objc methods.
+  func showObjCSelector(
+    _ command: ShowObjCSelectorCommand
+  ) async throws -> LSPAny {
+    let keys = self.keys
+
+    let uri = command.textDocument.uri
+    let snapshot = try self.documentManager.latestSnapshot(uri)
+    let position = command.positionRange.lowerBound
+    let offset = snapshot.utf8Offset(of: position)
+
+    let skreq = sourcekitd.dictionary([
+      keys.sourceFile: uri.pseudoPath,
+      keys.offset: offset,
+      keys.compilerArgs: await self.compileCommand(for: uri, fallbackAfterTimeout: true)?.compilerArgs
+        as [any SKDRequestValue]?,
+    ])
+
+    let dict = try await send(sourcekitdRequest: \.objcSelector, skreq, snapshot: snapshot)
+
+    guard let selector: String = dict[keys.text] else {
+      throw ResponseError.unknown("Could not retrieve Objective-C selector at cursor position")
+    }
+
+    if let sourceKitLSPServer {
+      sourceKitLSPServer.sendNotificationToClient(
+        ShowMessageNotification(type: .info, message: selector)
+      )
+    }
+
+    return .string(selector)
+  }
+}

Sources/SwiftLanguageService/ShowObjCSelectorCommand.swift

@@ -0,0 +1,67 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+@_spi(SourceKitLSP) package import LanguageServerProtocol
+
+/// Command to show the Objective-C selector for a Swift method marked with @objc.
+package struct ShowObjCSelectorCommand: SwiftCommand {
+  package static let identifier: String = "show.objc.selector.command"
+
+  package var title = "Show Objective-C Selector"
+
+  package var positionRange: Range<Position>
+  package var textDocument: TextDocumentIdentifier
+
+  package init(positionRange: Range<Position>, textDocument: TextDocumentIdentifier) {
+    self.positionRange = positionRange
+    self.textDocument = textDocument
+  }
+
+  package init?(fromLSPDictionary dictionary: [String: LSPAny]) {
+    guard case .dictionary(let documentDict)? = dictionary[CodingKeys.textDocument.stringValue],
+      case .string(let title)? = dictionary[CodingKeys.title.stringValue],
+      case .dictionary(let rangeDict)? = dictionary[CodingKeys.positionRange.stringValue]
+    else {
+      return nil
+    }
+
+    guard let positionRange = Range<Position>(fromLSPDictionary: rangeDict),
+      let textDocument = TextDocumentIdentifier(fromLSPDictionary: documentDict)
+    else {
+      return nil
+    }
+
+    self.init(
+      title: title,
+      positionRange: positionRange,
+      textDocument: textDocument
+    )
+  }
+
+  package init(
+    title: String,
+    positionRange: Range<Position>,
+    textDocument: TextDocumentIdentifier
+  ) {
+    self.title = title
+    self.positionRange = positionRange
+    self.textDocument = textDocument
+  }
+
+  package func encodeToLSPAny() -> LSPAny {
+    return .dictionary([
+      CodingKeys.title.stringValue: .string(title),
+      CodingKeys.positionRange.stringValue: positionRange.encodeToLSPAny(),
+      CodingKeys.textDocument.stringValue: textDocument.encodeToLSPAny(),
+    ])
+  }
+}

Sources/SwiftLanguageService/SwiftCommand.swift

@@ -51,6 +51,7 @@ extension SwiftLanguageService {
     [
       SemanticRefactorCommand.self,
       ExpandMacroCommand.self,
+      ShowObjCSelectorCommand.self,
     ].map { (command: any SwiftCommand.Type) in
       command.identifier
     }

Sources/SwiftLanguageService/SwiftLanguageService.swift

@@ -963,13 +963,13 @@ extension SwiftLanguageService {
 
     var canInlineMacro = false
 
-    var refactorActions = cursorInfoResponse.refactorActions.compactMap {
-      let lspCommand = $0.asCommand()
+    var refactorActions: [CodeAction] = cursorInfoResponse.refactorActions.compactMap { action in
+      let lspCommand = action.asCommand()
       if !canInlineMacro {
-        canInlineMacro = $0.actionString == "source.refactoring.kind.inline.macro"
+        canInlineMacro = action.actionString == "source.refactoring.kind.inline.macro"
       }
 
-      return CodeAction(title: $0.title, kind: .refactor, command: lspCommand)
+      return CodeAction(title: action.title, kind: .refactor, command: lspCommand)
     }
 
     if canInlineMacro {
@@ -979,6 +979,22 @@ extension SwiftLanguageService {
       refactorActions.append(CodeAction(title: expandMacroCommand.title, kind: .refactor, command: expandMacroCommand))
     }
 
+    let methodKinds: [SymbolKind] = [.method, .function, .constructor]
+    let isOnMethod = cursorInfoResponse.cursorInfo.contains { cursorInfo in
+      if let kind = cursorInfo.symbolInfo.kind {
+        return methodKinds.contains(kind)
+      }
+      return false
+    }
+
+    if isOnMethod {
+      let showCommand = ShowObjCSelectorCommand(
+        positionRange: params.range,
+        textDocument: params.textDocument
+      ).asCommand()
+      refactorActions.append(CodeAction(title: "Show Objective-C Selector", kind: .refactor, command: showCommand))
+    }
+
     return refactorActions
   }
 
@@ -1096,6 +1112,8 @@ extension SwiftLanguageService {
       try await semanticRefactoring(command)
     } else if let command = req.swiftCommand(ofType: ExpandMacroCommand.self) {
       try await expandMacro(command)
+    } else if let command = req.swiftCommand(ofType: ShowObjCSelectorCommand.self) {
+      return try await showObjCSelector(command)
     } else if let command = req.swiftCommand(ofType: RemoveUnusedImportsCommand.self) {
       try await removeUnusedImports(command)
     } else {