Add MoveMembersToExtension code action

Sources/SwiftLanguageService/CodeActions/SyntaxCodeActions.swift

@@ -27,6 +27,7 @@ let allSyntaxCodeActions: [any SyntaxCodeActionProvider.Type] = {
     ConvertZeroParameterFunctionToComputedProperty.self,
     FormatRawStringLiteral.self,
     MigrateToNewIfLetSyntax.self,
+    MoveMembersToExtension.self,
     OpaqueParameterToGeneric.self,
     RemoveSeparatorsFromIntegerLiteral.self,
   ]
@@ -37,5 +38,6 @@ let allSyntaxCodeActions: [any SyntaxCodeActionProvider.Type] = {
 }()
 
 let supersededSourcekitdRefactoringActions: Set<String> = [
-  "source.refactoring.kind.simplify.long.number.literal"  // Superseded by AddSeparatorsToIntegerLiteral
+  "source.refactoring.kind.move.members.to.extension",  // Superseded by MoveMembersToExtension
+  "source.refactoring.kind.simplify.long.number.literal",  // Superseded by AddSeparatorsToIntegerLiteral
 ]

Sources/SwiftLanguageService/CodeActions/SyntaxRefactoringCodeActionProvider.swift

@@ -128,6 +128,37 @@ extension ConvertZeroParameterFunctionToComputedProperty: SyntaxRefactoringCodeA
   }
 }
 
+extension MoveMembersToExtension: SyntaxRefactoringCodeActionProvider {
+  static func codeActions(in scope: SyntaxCodeActionScope) -> [CodeAction] {
+
+    guard let node = nodeToRefactor(in: scope) else {
+      return []
+    }
+
+    guard let sourceEdits = try? Self.textRefactor(syntax: node, in: Context(range: scope.range)) else {
+      return []
+    }
+
+    guard let workspaceEdit = sourceEdits.asWorkspaceEdit(snapshot: scope.snapshot) else {
+      return []
+    }
+
+    return [
+      CodeAction(
+        title: Self.title,
+        kind: .refactorExtract,
+        edit: workspaceEdit
+      )
+    ]
+  }
+
+  package static var title: String { "Move to extension" }
+
+  static func nodeToRefactor(in scope: SyntaxCodeActionScope) -> Input? {
+    return scope.file
+  }
+}
+
 extension ConvertComputedPropertyToZeroParameterFunction: SyntaxRefactoringCodeActionProvider {
   package static var title: String { "Convert to zero parameter function" }
 

Tests/SourceKitLSPTests/CodeActionTests.swift

@@ -1545,6 +1545,70 @@ final class CodeActionTests: SourceKitLSPTestCase {
     )
   }
 
+  func testMoveMembersToExtension() async throws {
+    let testClient = try await TestSourceKitLSPClient(capabilities: clientCapabilitiesWithCodeActionSupport)
+    let uri = DocumentURI(for: .swift)
+
+    let positions = testClient.openDocument(
+      """
+      1️⃣class Foo {
+        2️⃣func foo() {
+          print("Hello world!")
+        }3️⃣
+
+        func bar() {
+          print("Hello world!")
+        }
+      }4️⃣
+      """,
+      uri: uri
+    )
+
+    let request = CodeActionRequest(
+      range: positions["2️⃣"]..<positions["3️⃣"],
+      context: .init(),
+      textDocument: TextDocumentIdentifier(uri)
+    )
+    let result = try await testClient.send(request)
+
+    guard case .codeActions(let codeActions) = result else {
+      XCTFail("Expected code actions")
+      return
+    }
+
+    let expectedCodeAction = CodeAction(
+      title: "Move to extension",
+      kind: .refactorExtract,
+      diagnostics: nil,
+      edit: WorkspaceEdit(
+        changes: [
+          uri: [
+            TextEdit(
+              range: positions["1️⃣"]..<positions["4️⃣"],
+              newText: """
+                class Foo {
+
+                  func bar() {
+                    print("Hello world!")
+                  }
+                }
+
+                extension Foo {
+                  func foo() {
+                    print("Hello world!")
+                  }
+                }
+                """
+            )
+          ]
+        ]
+      ),
+      command: nil
+    )
+
+    XCTAssertTrue(codeActions.contains(expectedCodeAction))
+  }
+
   func testConvertFunctionZeroParameterToComputedProperty() async throws {
     let testClient = try await TestSourceKitLSPClient(capabilities: clientCapabilitiesWithCodeActionSupport)
     let uri = DocumentURI(for: .swift)