Implement textDocument/declaration

Sources/LanguageServerProtocol/CMakeLists.txt

@@ -28,6 +28,7 @@ add_library(LanguageServerProtocol STATIC
   Requests/CodeActionRequest.swift
   Requests/ColorPresentationRequest.swift
   Requests/CompletionRequest.swift
+  Requests/DeclarationRequest.swift
   Requests/DefinitionRequest.swift
   Requests/DocumentColorRequest.swift
   Requests/DocumentHighlightRequest.swift

Sources/LanguageServerProtocol/Messages.swift

@@ -29,6 +29,7 @@ public let builtinRequests: [_RequestType.Type] = [
   TypeHierarchyPrepareRequest.self,
   TypeHierarchySupertypesRequest.self,
   TypeHierarchySubtypesRequest.self,
+  DeclarationRequest.self,
   DefinitionRequest.self,
   ImplementationRequest.self,
   ReferencesRequest.self,

Sources/LanguageServerProtocol/Requests/DeclarationRequest.swift

@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2022 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 to find the declarations(s) of the symbol at the given location.
+///
+/// Looks up the symbol at the given position and returns a list of all
+/// declarations involving that symbol in the workspace.
+///
+/// This request differs from `DefinitionRequest` because a symbol usually has
+/// only one definition but potentially has many declarations involving that
+/// symbol. E.g. the definition of a type versus the forward declarations of that type.
+///
+/// - Parameters:
+///   - textDocument: The document in which to lookup the symbol location.
+///   - position: The document location at which to lookup symbol information.
+///
+/// - Returns: The location of the declaration(s).
+public struct DeclarationRequest: TextDocumentRequest, Hashable {
+  public static let method: String = "textDocument/declaration"
+  public typealias Response = LocationsOrLocationLinksResponse?
+
+  /// The document in which to lookup the symbol location.
+  public var textDocument: TextDocumentIdentifier
+
+  /// The document location at which to lookup symbol information.
+  public var position: Position
+
+  public init(textDocument: TextDocumentIdentifier, position: Position) {
+    self.textDocument = textDocument
+    self.position = position
+  }
+}

Sources/SKTestSupport/INPUTS/BasicCXX/Object.h

@@ -2,4 +2,4 @@ struct /*Object*/Object {
   int field;
 };
 
-struct Object * newObject();
+/*Object:decl:newObject*/struct Object * newObject();

Sources/SKTestSupport/INPUTS/BasicCXX/main.c

@@ -1,6 +1,6 @@
 #include /*Object:include:main*/"Object.h"
 
 int main(int argc, const char *argv[]) {
-  struct /*Object:ref:main*/Object *obj = newObject();
+  struct /*Object:ref:main*/Object *obj = /*Object:ref:newObject*/newObject();
   return obj->field;
 }

Sources/SourceKitLSP/Clang/ClangLanguageServer.swift

@@ -447,6 +447,13 @@ extension ClangLanguageServerShim {
     return true
   }
 
+  /// Returns true if the `ToolchainLanguageServer` will take ownership of the request.
+  public func declaration(_ req: Request<DeclarationRequest>) -> Bool {
+    // We handle it to provide jump-to-header support for #import/#include.
+    forwardRequestToClangdOnQueue(req)
+    return true
+  }
+
   func completion(_ req: Request<CompletionRequest>) {
     forwardRequestToClangdOnQueue(req)
   }

Sources/SourceKitLSP/SourceKitServer.swift

@@ -184,6 +184,7 @@ public final class SourceKitServer: LanguageServer {
     registerToolchainTextDocumentRequest(SourceKitServer.completion,
                                          CompletionList(isIncomplete: false, items: []))
     registerToolchainTextDocumentRequest(SourceKitServer.hover, nil)
+    registerToolchainTextDocumentRequest(SourceKitServer.declaration, .locations([]))
     registerToolchainTextDocumentRequest(SourceKitServer.definition, .locations([]))
     registerToolchainTextDocumentRequest(SourceKitServer.references, [])
     registerToolchainTextDocumentRequest(SourceKitServer.implementation, .locations([]))
@@ -658,6 +659,7 @@ extension SourceKitServer {
       )),
       colorProvider: .bool(true),
       foldingRangeProvider: .bool(!registry.clientHasDynamicFoldingRangeRegistration),
+      declarationProvider: .bool(true),
       executeCommandProvider: executeCommandOptions,
       workspace: WorkspaceServerCapabilities(workspaceFolders: .init(
         supported: true,
@@ -1247,6 +1249,16 @@ extension SourceKitServer {
     return .success(resolved.isEmpty ? fallback : resolved)
   }
 
+  func declaration(
+    _ req: Request<DeclarationRequest>,
+    workspace: Workspace,
+    languageService: ToolchainLanguageServer
+  ) {
+    guard languageService.declaration(req) else {
+      return req.reply(.locations([]))
+    }
+  }
+
   func definition(
     _ req: Request<DefinitionRequest>,
     workspace: Workspace,

Sources/SourceKitLSP/Swift/SwiftLanguageServer.swift

@@ -587,6 +587,11 @@ extension SwiftLanguageServer {
     return false
   }
 
+  public func declaration(_ request: Request<DeclarationRequest>) -> Bool {
+    // We don't handle it.
+    return false
+  }
+
   public func completion(_ req: Request<CompletionRequest>) {
     queue.async {
       self._completion(req)

Sources/SourceKitLSP/ToolchainLanguageServer.swift

@@ -84,6 +84,7 @@ public protocol ToolchainLanguageServer: AnyObject {
 
   /// Returns true if the `ToolchainLanguageServer` will take ownership of the request.
   func definition(_ request: Request<DefinitionRequest>) -> Bool
+  func declaration(_ request: Request<DeclarationRequest>) -> Bool
 
   func documentSymbolHighlight(_ req: Request<DocumentHighlightRequest>)
   func foldingRange(_ req: Request<FoldingRangeRequest>)

Tests/SourceKitLSPTests/SourceKitTests.swift

@@ -314,10 +314,7 @@ final class SKTests: XCTestCase {
       textDocument: mainLoc.docIdentifier, position: includePosition)
     let resp = try withExtendedLifetime(ws) { try ws.sk.sendSync(goToInclude) }
 
-    guard let locationsOrLinks = resp else {
-      XCTFail("No response for go-to-#include")
-      return
-    }
+    let locationsOrLinks = try XCTUnwrap(resp, "No response for go-to-#include")
     switch locationsOrLinks {
     case .locations(let locations):
       XCTAssert(!locations.isEmpty, "Found no locations for go-to-#include")
@@ -346,10 +343,7 @@ final class SKTests: XCTestCase {
       textDocument: refLoc.docIdentifier, position: refPos)
     let resp = try withExtendedLifetime(ws) { try ws.sk.sendSync(goToDefinition) }
 
-    guard let locationsOrLinks = resp else {
-      XCTFail("No response for go-to-definition")
-      return
-    }
+    let locationsOrLinks = try XCTUnwrap(resp, "No response for go-to-definition")
     switch locationsOrLinks {
     case .locations(let locations):
       XCTAssert(!locations.isEmpty, "Found no locations for go-to-definition")
@@ -363,4 +357,34 @@ final class SKTests: XCTestCase {
       }
     }
   }
+
+  func testClangdGoToDeclaration() throws {
+    guard let ws = try staticSourceKitTibsWorkspace(name: "BasicCXX") else { return }
+    guard ToolchainRegistry.shared.default?.clangd != nil else { return }
+
+    let mainLoc = ws.testLoc("Object:ref:newObject")
+    let expectedDoc = ws.testLoc("Object:decl:newObject").docIdentifier.uri
+    let includePosition =
+        Position(line: mainLoc.position.line, utf16index: mainLoc.utf16Column + 2)
+
+    try ws.openDocument(mainLoc.url, language: .c)
+
+    let goToInclude = DeclarationRequest(
+      textDocument: mainLoc.docIdentifier, position: includePosition)
+    let resp = try! ws.sk.sendSync(goToInclude)
+
+    let locationsOrLinks = try XCTUnwrap(resp, "No response for go-to-declaration")
+    switch locationsOrLinks {
+    case .locations(let locations):
+      XCTAssert(!locations.isEmpty, "Found no locations for go-to-declaration")
+      if let loc = locations.first {
+        XCTAssertEqual(loc.uri, expectedDoc)
+      }
+    case .locationLinks(let locationLinks):
+      XCTAssert(!locationLinks.isEmpty, "Found no location links for go-to-declaration")
+      if let link = locationLinks.first {
+        XCTAssertEqual(link.targetUri, expectedDoc)
+      }
+    }
+  }
 }