Add a request to check if SourceKit-LSP is currently performing any indexing

Author: ahoppen

Contributor Documentation/LSP Extensions.md

@@ -434,6 +434,27 @@ export interface DocumentTestsParams {
 }
 ```
 
+## `sourceKit/_isIndexing`
+
+Request from the client to the server querying whether SourceKit-LSP is currently performing an background indexing tasks, including target preparation.
+
+> [!IMPORTANT]
+> This request is experimental and may be modified or removed in future versions of SourceKit-LSP without notice. Do not rely on it.
+
+- params: `IsIndexingParams`
+- result: `IsIndexingResult`
+
+```ts
+export interface IsIndexingParams {}
+
+export interface IsIndexingResult {
+  /**
+   * Whether SourceKit-LSP is currently performing an indexing task.
+   */
+  indexing: boolean;
+}
+```
+
 ## `window/didChangeActiveDocument`
 
 New notification from the client to the server, telling SourceKit-LSP which document is the currently active primary document.

Documentation/Configuration File.md

@@ -53,7 +53,7 @@ The structure of the file is currently not guaranteed to be stable. Options may
   - `noLazy`: Prepare a target without generating object files but do not do lazy type checking and function body skipping. This uses SwiftPM's `--experimental-prepare-for-indexing-no-lazy` flag.
   - `enabled`: Prepare a target without generating object files.
 - `cancelTextDocumentRequestsOnEditAndClose: boolean`: Whether sending a `textDocument/didChange` or `textDocument/didClose` notification for a document should cancel all pending requests for that document.
-- `experimentalFeatures: ("on-type-formatting"|"set-options-request"|"sourcekit-options-request")[]`: Experimental features that are enabled.
+- `experimentalFeatures: ("on-type-formatting"|"set-options-request"|"sourcekit-options-request"|"is-indexing-request")[]`: Experimental features that are enabled.
 - `swiftPublishDiagnosticsDebounceDuration: number`: The time that `SwiftLanguageService` should wait after an edit before starting to compute diagnostics and sending a `PublishDiagnosticsNotification`.
 - `workDoneProgressDebounceDuration: number`: When a task is started that should be displayed to the client as a work done progress, how many milliseconds to wait before actually starting the work done progress. This prevents flickering of the work done progress in the client for short-lived index tasks which end within this duration.
 - `sourcekitdRequestTimeout: number`: The maximum duration that a sourcekitd request should be allowed to execute before being declared as timed out. In general, editors should cancel requests that they are no longer interested in, but in case editors don't cancel requests, this ensures that a long-running non-cancelled request is not blocking sourcekitd and thus most semantic functionality. In particular, VS Code does not cancel the semantic tokens request, which can cause a long-running AST build that blocks sourcekitd.

Sources/LanguageServerProtocol/CMakeLists.txt

@@ -67,6 +67,7 @@ add_library(LanguageServerProtocol STATIC
   Requests/InlayHintResolveRequest.swift
   Requests/InlineValueRefreshRequest.swift
   Requests/InlineValueRequest.swift
+  Requests/IsIndexingRequest.swift
   Requests/LinkedEditingRangeRequest.swift
   Requests/MonikersRequest.swift
   Requests/PeekDocumentsRequest.swift

Sources/LanguageServerProtocol/Messages.swift

@@ -58,6 +58,7 @@ public let builtinRequests: [_RequestType.Type] = [
   InlayHintResolveRequest.self,
   InlineValueRefreshRequest.self,
   InlineValueRequest.self,
+  IsIndexingRequest.self,
   LinkedEditingRangeRequest.self,
   MonikersRequest.self,
   PeekDocumentsRequest.self,

Sources/LanguageServerProtocol/Requests/IsIndexingRequest.swift

@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2025 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
+//
+//===----------------------------------------------------------------------===//
+
+public struct IsIndexingRequest: RequestType {
+  public static let method: String = "sourceKit/_isIndexing"
+  public typealias Response = IsIndexingResponse
+
+  public init() {}
+}
+
+public struct IsIndexingResponse: ResponseType {
+  /// Whether SourceKit-LSP is currently performing an indexing task.
+  public var indexing: Bool
+
+  public init(indexing: Bool) {
+    self.indexing = indexing
+  }
+}

Sources/SKOptions/ExperimentalFeatures.swift

@@ -22,4 +22,7 @@ public enum ExperimentalFeature: String, Codable, Sendable, CaseIterable {
 
   /// Enable the `workspace/_sourceKitOptions` request.
   case sourceKitOptionsRequest = "sourcekit-options-request"
+
+  /// Enable the `sourceKit/_isIndexing` request.
+  case isIndexingRequest = "is-indexing-request"
 }

Sources/SemanticIndex/SemanticIndexManager.swift

@@ -93,7 +93,7 @@ package enum IndexTaskStatus: Comparable {
 /// In reality, these status are not exclusive. Eg. the index might be preparing one target for editor functionality,
 /// re-generating the build graph and indexing files at the same time. To avoid showing too many concurrent status
 /// messages to the user, we only show the highest priority task.
-package enum IndexProgressStatus: Sendable {
+package enum IndexProgressStatus: Sendable, Equatable {
   case preparingFileForEditorFunctionality
   case schedulingIndexing
   case indexing(preparationTasks: [BuildTargetIdentifier: IndexTaskStatus], indexTasks: [DocumentURI: IndexTaskStatus])

Sources/SourceKitLSP/MessageHandlingDependencyTracker.swift

@@ -206,6 +206,8 @@ package enum MessageHandlingDependencyTracker: QueueBasedMessageHandlerDependenc
       self = .freestanding
     case is InlineValueRefreshRequest:
       self = .freestanding
+    case is IsIndexingRequest:
+      self = .freestanding
     case is PollIndexRequest:
       self = .globalConfigurationChange
     case is RenameRequest:

Sources/SourceKitLSP/SourceKitLSPServer.swift

@@ -824,6 +824,8 @@ extension SourceKitLSPServer: QueueBasedMessageHandler {
       initialized = true
     case let request as RequestAndReply<InlayHintRequest>:
       await self.handleRequest(for: request, requestHandler: self.inlayHint)
+    case let request as RequestAndReply<IsIndexingRequest>:
+      await request.reply { try await self.isIndexing(request.params) }
     case let request as RequestAndReply<PollIndexRequest>:
       await request.reply { try await pollIndex(request.params) }
     case let request as RequestAndReply<PrepareRenameRequest>:
@@ -1270,6 +1272,17 @@ extension SourceKitLSPServer {
     )
   }
 
+  func isIndexing(_ request: IsIndexingRequest) async throws -> IsIndexingResponse {
+    guard self.options.hasExperimentalFeature(.isIndexingRequest) else {
+      throw ResponseError.unknown("\(IsIndexingRequest.method) indexing is an experimental request")
+    }
+    let isIndexing =
+      await workspaces
+      .compactMap(\.semanticIndexManager)
+      .asyncContains { await $0.progressStatus != .upToDate }
+    return IsIndexingResponse(indexing: isIndexing)
+  }
+
   // MARK: - Text synchronization
 
   func openDocument(_ notification: DidOpenTextDocumentNotification) async {

Tests/SourceKitLSPTests/BackgroundIndexingTests.swift

@@ -1883,6 +1883,33 @@ final class BackgroundIndexingTests: XCTestCase {
       ) != nil
     }
   }
+
+  func testIsIndexingRequest() async throws {
+    let checkedIsIndexStatus = AtomicBool(initialValue: false)
+    let hooks = Hooks(
+      indexHooks: IndexHooks(updateIndexStoreTaskDidStart: { task in
+        while !checkedIsIndexStatus.value {
+          try? await Task.sleep(for: .seconds(0.1))
+        }
+      })
+    )
+    let project = try await SwiftPMTestProject(
+      files: [
+        "Test.swift": ""
+      ],
+      options: .testDefault(experimentalFeatures: [.isIndexingRequest]),
+      hooks: hooks,
+      enableBackgroundIndexing: true,
+      pollIndex: false
+    )
+    let isIndexingResponseWhileIndexing = try await project.testClient.send(IsIndexingRequest())
+    XCTAssert(isIndexingResponseWhileIndexing.indexing)
+    checkedIsIndexStatus.value = true
+
+    try await repeatUntilExpectedResult {
+      try await project.testClient.send(IsIndexingRequest()).indexing == false
+    }
+  }
 }
 
 extension HoverResponseContents {

config.schema.json

@@ -71,12 +71,14 @@
         "enum" : [
           "on-type-formatting",
           "set-options-request",
-          "sourcekit-options-request"
+          "sourcekit-options-request",
+          "is-indexing-request"
         ],
         "markdownEnumDescriptions" : [
           "Enable support for the `textDocument\/onTypeFormatting` request.",
           "Enable support for the `workspace\/_setOptions` request.",
-          "Enable the `workspace\/_sourceKitOptions` request."
+          "Enable the `workspace\/_sourceKitOptions` request.",
+          "Enable the `sourceKit\/_isIndexing` request."
         ],
         "type" : "string"
       },