Time out updating the index store after 2 minutes

Time out updating of the index store after 2 minutes. We don't expect any single file compilation to take longer than 2 minutes in practice, so this indicates that the compiler has entered some kind of loop. We will try indexing the file again when it is edited or when the project is re-opened.

rdar://128732571

Author: ahoppen

Sources/SKSupport/AsyncUtils.swift

@@ -166,3 +166,28 @@ extension Collection where Element: Sendable {
     }
   }
 }
+
+public struct TimeoutError: Error, CustomStringConvertible {
+  public var description: String { "Timed out" }
+}
+
+/// Executes `body`. If it doesn't finish after `duration`, throws a `TimeoutError`.
+public func withTimeout<T: Sendable>(
+  _ duration: Duration,
+  _ body: @escaping @Sendable () async throws -> T
+) async throws -> T {
+  try await withThrowingTaskGroup(of: T.self) { taskGroup in
+    taskGroup.addTask {
+      try await Task.sleep(for: duration)
+      throw TimeoutError()
+    }
+    taskGroup.addTask {
+      return try await body()
+    }
+    for try await value in taskGroup {
+      taskGroup.cancelAll()
+      return value
+    }
+    throw CancellationError()
+  }
+}

Sources/SemanticIndex/UpdateIndexStoreTaskDescription.swift

@@ -321,7 +321,13 @@ public struct UpdateIndexStoreTaskDescription: IndexTaskDescription {
       arguments: processArguments,
       workingDirectory: workingDirectory
     )
-    let result = try await process.waitUntilExitSendingSigIntOnTaskCancellation()
+    // Time out updating of the index store after 2 minutes. We don't expect any single file compilation to take longer
+    // than 2 minutes in practice, so this indicates that the compiler has entered a loop and we probably won't make any
+    // progress here. We will try indexing the file again when it is edited or when the project is re-opened.
+    // 2 minutes have been chosen arbitrarily.
+    let result = try await withTimeout(.seconds(120)) {
+      try await process.waitUntilExitSendingSigIntOnTaskCancellation()
+    }
 
     indexProcessDidProduceResult(
       IndexProcessResult(

Tests/SKSupportTests/AsyncUtilsTests.swift

@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2018 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
+//
+//===----------------------------------------------------------------------===//
+
+import LSPTestSupport
+import SKSupport
+import XCTest
+
+final class AsyncUtilsTests: XCTestCase {
+  func testWithTimeout() async throws {
+    let expectation = self.expectation(description: "withTimeout body finished")
+    await assertThrowsError(
+      try await withTimeout(.seconds(0.1)) {
+        try? await Task.sleep(for: .seconds(10))
+        XCTAssert(Task.isCancelled)
+        expectation.fulfill()
+      }
+    ) { error in
+      XCTAssert(error is TimeoutError, "Received unexpected error \(error)")
+    }
+    try await fulfillmentOfOrThrow([expectation])
+  }
+}