[Commands] Prototype swift fixit — a subcommand to deserialize diagnostics and apply fix-its

Author: AnthonyLatsis

Package.swift

@@ -304,6 +304,21 @@ let package = Package(
             ]
         ),
 
+        .target(
+            /** The backing API for `SwiftFixItCommand` */
+            name: "SwiftFixIt",
+            dependencies: [
+                "Basics",
+                .product(name: "TSCBasic", package: "swift-tools-support-core"),
+            ] + swiftSyntaxDependencies(
+                ["SwiftDiagnostics", "SwiftIDEUtils", "SwiftParser", "SwiftSyntax"]
+            ),
+            exclude: ["CMakeLists.txt"],
+            swiftSettings: commonExperimentalFeatures + [
+                .unsafeFlags(["-static"]),
+            ]
+        ),
+
         // MARK: Project Model
 
         .target(
@@ -573,6 +588,7 @@ let package = Package(
                 "Workspace",
                 "XCBuildSupport",
                 "SwiftBuildSupport",
+                "SwiftFixIt",
             ] + swiftSyntaxDependencies(["SwiftIDEUtils"]),
             exclude: ["CMakeLists.txt", "README.md"],
             swiftSettings: swift6CompatibleExperimentalFeatures + [
@@ -730,6 +746,12 @@ let package = Package(
                 "Workspace",
             ]
         ),
+        .executableTarget(
+            /** Deserializes diagnostics and applies fix-its */
+            name: "swift-fixit",
+            dependencies: ["Commands"],
+            exclude: ["CMakeLists.txt"]
+        ),
 
         // MARK: Support for Swift macros, should eventually move to a plugin-based solution
 
@@ -916,6 +938,10 @@ let package = Package(
             dependencies: ["SourceControl", "_InternalTestSupport"],
             exclude: ["Inputs/TestRepo.tgz"]
         ),
+        .testTarget(
+            name: "SwiftFixItTests",
+            dependencies: ["SwiftFixIt", "_InternalTestSupport"]
+        ),
         .testTarget(
             name: "XCBuildSupportTests",
             dependencies: ["XCBuildSupport", "_InternalTestSupport", "_InternalBuildTestSupport"],

Sources/Commands/CMakeLists.txt

@@ -40,6 +40,7 @@ add_library(Commands
   Snippets/Card.swift
   Snippets/Colorful.swift
   SwiftBuildCommand.swift
+  SwiftFixItCommand.swift
   SwiftRunCommand.swift
   SwiftTestCommand.swift
   CommandWorkspaceDelegate.swift

Sources/Commands/SwiftFixitCommand.swift

@@ -0,0 +1,66 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import struct ArgumentParser.Argument
+import protocol ArgumentParser.AsyncParsableCommand
+import struct ArgumentParser.CommandConfiguration
+import struct ArgumentParser.OptionGroup
+import protocol ArgumentParser.ParsableArguments
+
+import struct Basics.AbsolutePath
+import var Basics.localFileSystem
+import struct Basics.SwiftVersion
+
+import struct CoreCommands.LoggingOptions
+
+import struct SwiftFixIt.SwiftFixIt
+
+private struct Options: ParsableArguments {
+    @OptionGroup(title: "Logging")
+    var logging: LoggingOptions
+
+    @Argument(
+        help: "",
+        completion: .file(extensions: [".dia"])
+    )
+    var diagnosticFiles: [AbsolutePath] = []
+}
+
+/// Deserializes `.dia` files and applies all fix-its in place.
+package struct SwiftFixitCommand: AsyncParsableCommand {
+    package static var configuration = CommandConfiguration(
+        commandName: "fixit",
+        _superCommandName: "swift",
+        abstract: "Deserialize diagnostics and apply fix-its",
+        version: SwiftVersion.current.completeDisplayString,
+        helpNames: [
+            .short,
+            .long,
+            .customLong("help", withSingleDash: true),
+        ]
+    )
+
+    @OptionGroup
+    fileprivate var options: Options
+
+    package init() {}
+
+    package func run() async throws {
+        if self.options.diagnosticFiles.isEmpty {
+            return
+        }
+
+        let swiftFixIt = try SwiftFixIt(diagnosticFiles: options.diagnosticFiles, fileSystem: localFileSystem)
+
+        try swiftFixIt.applyFixIts()
+    }
+}

Sources/SwiftFixIt/CMakeLists.txt

@@ -0,0 +1,24 @@
+# This source file is part of the Swift open source project
+#
+# Copyright (c) 2025 Apple Inc. and the Swift project authors
+# Licensed under Apache License v2.0 with Runtime Library Exception
+#
+# See http://swift.org/LICENSE.txt for license information
+# See http://swift.org/CONTRIBUTORS.txt for Swift project authors
+
+add_library(SwiftFixIt STATIC
+  SwiftFixIt.swift)
+target_link_libraries(SwiftFixIt PUBLIC
+  Basics
+
+  SwiftSyntax::SwiftDiagnostics
+  SwiftSyntax::SwiftIDEUtils
+  SwiftSyntax::SwiftParser
+  SwiftSyntax::SwiftSyntax
+
+  TSCBasic
+  TSCUtility
+)
+
+set_target_properties(SwiftFixIt PROPERTIES
+  INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_Swift_MODULE_DIRECTORY})