Resolve /usr/bin/* shims on macOS

CMake was previously doing this itself before 4.0, but seems to be
inserting `/usr/bin/*` now. Resolve the `/usr/bin` trampoline ourselves
in a similar fashion to swiftly (but with xcrun).

Resolves rdar://163462990.

Author: bnbarham

Sources/BuildServerIntegration/CMakeLists.txt

@@ -20,8 +20,8 @@ add_library(BuildServerIntegration STATIC
   LegacyBuildServer.swift
   MainFilesProvider.swift
   SplitShellCommand.swift
-  SwiftlyResolver.swift
-  SwiftPMBuildServer.swift)
+  SwiftPMBuildServer.swift
+  SwiftToolchainResolver.swift)
 set_target_properties(BuildServerIntegration PROPERTIES
   INTERFACE_INCLUDE_DIRECTORIES ${CMAKE_Swift_MODULE_DIRECTORY})
 target_link_libraries(BuildServerIntegration PUBLIC

Sources/BuildServerIntegration/JSONCompilationDatabaseBuildServer.swift

@@ -26,20 +26,20 @@ fileprivate extension CompilationDatabaseCompileCommand {
   ///
   /// The absence of a compiler means we have an empty command line, which should never happen.
   ///
-  /// If the compiler is a symlink to `swiftly`, it uses `swiftlyResolver` to find the corresponding executable in a
-  /// real toolchain and returns that executable.
-  func compiler(swiftlyResolver: SwiftlyResolver, compileCommandsDirectory: URL) async -> String? {
+  /// If the compiler is a symlink to `swiftly` or in `/usr/bin` on macOS, it uses `toolchainResolver` to find the
+  /// corresponding executable in a real toolchain and returns that executable.
+  func compiler(toolchainResolver: SwiftToolchainResolver, compileCommandsDirectory: URL) async -> String? {
     guard let compiler = commandLine.first else {
       return nil
     }
-    let swiftlyResolved = await orLog("Resolving swiftly") {
-      try await swiftlyResolver.resolve(
+    let resolved = await orLog("Resolving compiler") {
+      try await toolchainResolver.resolve(
         compiler: URL(fileURLWithPath: compiler),
         workingDirectory: directoryURL(compileCommandsDirectory: compileCommandsDirectory)
       )?.filePath
     }
-    if let swiftlyResolved {
-      return swiftlyResolved
+    if let resolved {
+      return resolved
     }
     return compiler
   }
@@ -74,7 +74,7 @@ package actor JSONCompilationDatabaseBuildServer: BuiltInBuildServer {
   /// finds the compilation database in a build directory.
   private var configDirectory: URL
 
-  private let swiftlyResolver = SwiftlyResolver()
+  private let toolchainResolver = SwiftToolchainResolver()
 
   // Watch for all all changes to `compile_commands.json` and `compile_flags.txt` instead of just the one at
   // `configPath` so that we cover the following semi-common scenario:
@@ -124,7 +124,7 @@ package actor JSONCompilationDatabaseBuildServer: BuiltInBuildServer {
   package func buildTargets(request: WorkspaceBuildTargetsRequest) async throws -> WorkspaceBuildTargetsResponse {
     let compilers = Set(
       await compdb.commands.asyncCompactMap { (command) -> String? in
-        await command.compiler(swiftlyResolver: swiftlyResolver, compileCommandsDirectory: configDirectory)
+        await command.compiler(toolchainResolver: toolchainResolver, compileCommandsDirectory: configDirectory)
       }
     ).sorted { $0 < $1 }
     let targets = try await compilers.asyncMap { compiler in
@@ -155,7 +155,7 @@ package actor JSONCompilationDatabaseBuildServer: BuiltInBuildServer {
       }
       let commandsWithRequestedCompilers = await compdb.commands.lazy.asyncFilter { command in
         return await targetCompiler
-          == command.compiler(swiftlyResolver: swiftlyResolver, compileCommandsDirectory: configDirectory)
+          == command.compiler(toolchainResolver: toolchainResolver, compileCommandsDirectory: configDirectory)
       }
       let sources = commandsWithRequestedCompilers.map {
         SourceItem(uri: $0.uri(compileCommandsDirectory: configDirectory), kind: .file, generated: false)
@@ -171,7 +171,7 @@ package actor JSONCompilationDatabaseBuildServer: BuiltInBuildServer {
       self.reloadCompilationDatabase()
     }
     if notification.changes.contains(where: { $0.uri.fileURL?.lastPathComponent == ".swift-version" }) {
-      await swiftlyResolver.clearCache()
+      await toolchainResolver.clearCache()
       connectionToSourceKitLSP.send(OnBuildTargetDidChangeNotification(changes: nil))
     }
   }
@@ -185,7 +185,7 @@ package actor JSONCompilationDatabaseBuildServer: BuiltInBuildServer {
   ) async throws -> TextDocumentSourceKitOptionsResponse? {
     let targetCompiler = try request.target.compileCommandsCompiler
     let command = await compdb[request.textDocument.uri].asyncFilter {
-      return await $0.compiler(swiftlyResolver: swiftlyResolver, compileCommandsDirectory: configDirectory)
+      return await $0.compiler(toolchainResolver: toolchainResolver, compileCommandsDirectory: configDirectory)
         == targetCompiler
     }.first
     guard let command else {

Sources/BuildServerIntegration/SwiftlyResolver.swift renamed to Sources/BuildServerIntegration/SwiftToolchainResolver.swift

@@ -18,56 +18,86 @@ import TSCExtensions
 import struct TSCBasic.AbsolutePath
 import class TSCBasic.Process
 
-/// Given a path to a compiler, which might be a symlink to `swiftly`, this type determines the compiler executable in
-/// an actual toolchain. It also caches the results. The client needs to invalidate the cache if the path that swiftly
-/// might resolve to has changed, eg. because `.swift-version` has been updated.
-actor SwiftlyResolver {
+/// Given a path to a compiler, which might be a symlink to `swiftly` or `/usr/bin` on macOS, this type determines the
+/// compiler executable in an actual toolchain and caches the result. The client needs to invalidate the cache if the
+/// path that this may resolve to has changed, eg. because `.swift-version` or `SDKROOT` has been updated.
+actor SwiftToolchainResolver {
   private struct CacheKey: Hashable {
     let compiler: URL
     let workingDirectory: URL?
   }
 
   private var cache: LRUCache<CacheKey, Result<URL?, Error>> = LRUCache(capacity: 100)
 
-  /// Check if `compiler` is a symlink to `swiftly`. If so, find the executable in the toolchain that swiftly resolves
-  /// to within the given working directory and return the URL of the corresponding compiler in that toolchain.
-  /// If `compiler` does not resolve to `swiftly`, return `nil`.
+  /// Check if `compiler` is a symlink to `swiftly` or in `/usr/bin` on macOS. If so, find the executable in the
+  /// toolchain that would be resolved to within the given working directory and return the URL of the corresponding
+  /// compiler in that toolchain. If `compiler` does not resolve to `swiftly` or `/usr/bin` on macOS, return `nil`.
   func resolve(compiler: URL, workingDirectory: URL?) async throws -> URL? {
-    let cacheKey = CacheKey(compiler: compiler, workingDirectory: workingDirectory)
+    let cacheKey: CacheKey = CacheKey(compiler: compiler, workingDirectory: workingDirectory)
     if let cached = cache[cacheKey] {
       return try cached.get()
     }
+
     let computed: Result<URL?, Error>
     do {
-      computed = .success(
-        try await resolveSwiftlyTrampolineImpl(compiler: compiler, workingDirectory: workingDirectory)
-      )
+      var resolved = try await resolveSwiftlyTrampoline(compiler: compiler, workingDirectory: workingDirectory)
+      if resolved == nil {
+        resolved = try await resolveXcrunTrampoline(compiler: compiler, workingDirectory: workingDirectory)
+      }
+
+      computed = .success(resolved)
     } catch {
       computed = .failure(error)
     }
+
     cache[cacheKey] = computed
     return try computed.get()
   }
 
-  private func resolveSwiftlyTrampolineImpl(compiler: URL, workingDirectory: URL?) async throws -> URL? {
+  private func resolveSwiftlyTrampoline(compiler: URL, workingDirectory: URL?) async throws -> URL? {
     let realpath = try compiler.realpath
     guard realpath.lastPathComponent == "swiftly" else {
       return nil
     }
+
     let swiftlyResult = try await Process.run(
       arguments: [realpath.filePath, "use", "-p"],
       workingDirectory: try AbsolutePath(validatingOrNil: workingDirectory?.filePath)
     )
     let swiftlyToolchain = URL(
       fileURLWithPath: try swiftlyResult.utf8Output().trimmingCharacters(in: .whitespacesAndNewlines)
     )
+
     let resolvedCompiler = swiftlyToolchain.appending(components: "usr", "bin", compiler.lastPathComponent)
     if FileManager.default.fileExists(at: resolvedCompiler) {
       return resolvedCompiler
     }
     return nil
   }
 
+  private func resolveXcrunTrampoline(compiler: URL, workingDirectory: URL?) async throws -> URL? {
+    #if !os(macOS)
+    return nil
+    #endif
+
+    guard compiler.deletingLastPathComponent() == URL(fileURLWithPath: "/usr/bin") else {
+      return nil
+    }
+
+    let xcrunResult = try await Process.run(
+      arguments: ["xcrun", "-f", compiler.lastPathComponent],
+      workingDirectory: try AbsolutePath(validatingOrNil: workingDirectory?.filePath)
+    )
+
+    let resolvedCompiler = URL(
+      fileURLWithPath: try xcrunResult.utf8Output().trimmingCharacters(in: .whitespacesAndNewlines)
+    )
+    if FileManager.default.fileExists(at: resolvedCompiler) {
+      return resolvedCompiler
+    }
+    return nil
+  }
+
   func clearCache() {
     cache.removeAll()
   }

Tests/SourceKitLSPTests/CompilationDatabaseTests.swift

@@ -261,10 +261,10 @@ final class CompilationDatabaseTests: SourceKitLSPTestCase {
         libIndexStore: nil
       )
       let toolchainRegistry = ToolchainRegistry(toolchains: [
-        try await unwrap(ToolchainRegistry.forTesting.default), fakeToolchain,
+        defaultToolchain, fakeToolchain,
       ])
 
-      // We need to create a file for the swift executable because `SwiftlyResolver` checks for its presence.
+      // We need to create a file for the swift executable because `SwiftToolchainResolver` checks for its presence.
       try FileManager.default.createDirectory(
         at: XCTUnwrap(fakeToolchain.swift).deletingLastPathComponent(),
         withIntermediateDirectories: true
@@ -389,6 +389,43 @@ final class CompilationDatabaseTests: SourceKitLSPTestCase {
     )
     XCTAssertEqual(definition?.locations, [try project.location(from: "1️⃣", to: "2️⃣", in: "header.h")])
   }
+
+  func testLookThroughXcrun() async throws {
+    try SkipUnless.platformIsDarwin("xcrun is macOS only")
+
+    try await withTestScratchDir { scratchDirectory in
+      let toolchainRegistry = try XCTUnwrap(ToolchainRegistry.forTesting)
+
+      let project = try await MultiFileTestProject(
+        files: [
+          "test.swift": """
+          #warning("Test warning")
+          """,
+          "compile_commands.json": """
+          [
+            {
+              "directory": "$TEST_DIR_BACKSLASH_ESCAPED",
+              "arguments": [
+                "/usr/bin/swiftc",
+                "$TEST_DIR_BACKSLASH_ESCAPED/test.swift",
+                \(defaultSDKArgs)
+              ],
+              "file": "test.swift",
+              "output": "$TEST_DIR_BACKSLASH_ESCAPED/test.swift.o"
+            }
+          ]
+          """,
+        ],
+        toolchainRegistry: toolchainRegistry
+      )
+
+      let (uri, _) = try project.openDocument("test.swift")
+      let diagnostics = try await project.testClient.send(
+        DocumentDiagnosticsRequest(textDocument: TextDocumentIdentifier(uri))
+      )
+      XCTAssertEqual(diagnostics.fullReport?.items.map(\.message), ["Test warning"])
+    }
+  }
 }
 
 private let defaultSDKArgs: String = {