Add LSP extension request for retrieving macro expansions

Sources/LanguageServerProtocol/CMakeLists.txt

@@ -64,6 +64,7 @@ add_library(LanguageServerProtocol STATIC
   Requests/InlineValueRefreshRequest.swift
   Requests/InlineValueRequest.swift
   Requests/LinkedEditingRangeRequest.swift
+  Requests/MacroExpansionRequest.swift
   Requests/MonikersRequest.swift
   Requests/OpenInterfaceRequest.swift
   Requests/PollIndexRequest.swift
@@ -107,6 +108,7 @@ add_library(LanguageServerProtocol STATIC
   SupportTypes/LocationLink.swift
   SupportTypes/LocationsOrLocationLinksResponse.swift
   SupportTypes/LSPAny.swift
+  SupportTypes/MacroExpansion.swift
   SupportTypes/MarkupContent.swift
   SupportTypes/NotebookCellTextDocumentFilter.swift
   SupportTypes/NotebookDocument.swift

Sources/LanguageServerProtocol/Messages.swift

@@ -55,6 +55,7 @@ public let builtinRequests: [_RequestType.Type] = [
   InlineValueRefreshRequest.self,
   InlineValueRequest.self,
   LinkedEditingRangeRequest.self,
+  MacroExpansionRequest.self,
   MonikersRequest.self,
   OpenInterfaceRequest.self,
   PollIndexRequest.self,

Sources/LanguageServerProtocol/Requests/MacroExpansionRequest.swift

@@ -0,0 +1,39 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 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
+//
+//===----------------------------------------------------------------------===//
+
+/// Request the expansion of the macro at a given use site.
+/// **LSP Extension**.
+///
+/// - Parameters:
+///   - textDocument: The document in which the macro is used.
+///   - range: The range at which the macro is used.
+///
+/// - Returns: The macro expansion.
+public struct MacroExpansionRequest: TextDocumentRequest, Hashable {
+  public static let method: String = "sourcekit-lsp/macroExpansion"
+  public typealias Response = MacroExpansion?
+
+  /// The document in which the macro is used.
+  public var textDocument: TextDocumentIdentifier
+
+  /// The position at which the macro is used.
+  @CustomCodable<PositionRange>
+  public var range: Range<Position>
+
+  public init(
+    textDocument: TextDocumentIdentifier,
+    range: Range<Position>
+  ) {
+    self.textDocument = textDocument
+    self._range = CustomCodable(wrappedValue: range)
+  }
+}

Sources/LanguageServerProtocol/SupportTypes/MacroExpansion.swift

@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 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
+//
+//===----------------------------------------------------------------------===//
+
+/// The expansion of a macro in a source file.
+public struct MacroExpansion: ResponseType, Hashable {
+  /// The position in the source file where the expansion would be inserted.
+  public let position: Position
+
+  /// The Swift code that the macro expands to.
+  public let sourceText: String
+
+  public init(position: Position, sourceText: String) {
+    self.position = position
+    self.sourceText = sourceText
+  }
+}

Sources/SourceKitLSP/Clang/ClangLanguageServer.swift

@@ -572,6 +572,10 @@ extension ClangLanguageServerShim {
     return try await forwardRequestToClangd(req)
   }
 
+  func macroExpansion(_ req: MacroExpansionRequest) async throws -> MacroExpansion? {
+    return nil
+  }
+
   func foldingRange(_ req: FoldingRangeRequest) async throws -> [FoldingRange]? {
     guard self.capabilities?.foldingRangeProvider?.isSupported ?? false else {
       return nil

Sources/SourceKitLSP/SourceKitServer.swift

@@ -624,6 +624,8 @@ extension SourceKitServer: MessageHandler {
           requestHandler: self.documentDiagnostic,
           fallback: .full(.init(items: []))
         )
+      case let request as Request<MacroExpansionRequest>:
+        await self.handleRequest(for: request, requestHandler: self.macroExpansion, fallback: nil)
       default:
         reply(.failure(ResponseError.methodNotFound(R.method)))
       }
@@ -1386,6 +1388,14 @@ extension SourceKitServer {
     return try await languageService.documentDiagnostic(req)
   }
 
+  func macroExpansion(
+    _ request: MacroExpansionRequest,
+    workspace: Workspace,
+    languageService: ToolchainLanguageServer
+  ) async throws -> MacroExpansion? {
+    return try await languageService.macroExpansion(request)
+  }
+
   /// Converts a location from the symbol index to an LSP location.
   ///
   /// - Parameter location: The symbol index location

Sources/SourceKitLSP/Swift/SwiftLanguageServer.swift

@@ -1299,6 +1299,30 @@ extension SwiftLanguageServer {
     return .full(RelatedFullDocumentDiagnosticReport(items: diagnostics))
   }
 
+  public func macroExpansion(_ req: MacroExpansionRequest) async throws -> MacroExpansion? {
+    let command = SemanticRefactorCommand(
+      title: "Expand Macro",
+      actionString: "source.refactoring.kind.expand.macro",
+      positionRange: req.range,
+      textDocument: req.textDocument
+    )
+
+    do {
+      let refactor = try await semanticRefactoring(command)
+
+      guard let edit = refactor.edit.changes?[req.textDocument.uri]?.first else {
+        return nil
+      }
+
+      return MacroExpansion(
+        position: edit.range.lowerBound,
+        sourceText: edit.newText
+      )
+    } catch SemanticRefactoringError.noEditsNeeded(_) {
+      return nil
+    }
+  }
+
   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 sourceKitServer else {

Sources/SourceKitLSP/ToolchainLanguageServer.swift

@@ -104,6 +104,7 @@ public protocol ToolchainLanguageServer: AnyObject {
   func codeAction(_ req: CodeActionRequest) async throws -> CodeActionRequestResponse?
   func inlayHint(_ req: InlayHintRequest) async throws -> [InlayHint]
   func documentDiagnostic(_ req: DocumentDiagnosticsRequest) async throws -> DocumentDiagnosticReport
+  func macroExpansion(_ req: MacroExpansionRequest) async throws -> MacroExpansion?
 
   // MARK: - Other