Add config option for trailing closure rewriting

Documentation/Configuration File.md

@@ -39,6 +39,8 @@ The structure of the file is currently not guaranteed to be stable. Options may
     - `indexPrefixMap: [string: string]`: Path remappings for remapping index data for local use.
     - `maxCoresPercentageToUseForBackgroundIndexing: double`: A hint indicating how many cores background indexing should use at most (value between 0 and 1). Background indexing is not required to honor this setting
     - `updateIndexStoreTimeout: int`: Number of seconds to wait for an update index store task to finish before killing it.
+- `codeCompletion`: Dictionary with the following keys, defining options related to code completion actions
+    - `rewriteTrailingClosures: "full"|"never"`: Whether to pre-expand trailing closures when completing a function call expression
 - `logging`: Dictionary with the following keys, changing SourceKit-LSP’s logging behavior on non-Apple platforms. On Apple platforms, logging is done through the [system log](Diagnose%20Bundle.md#Enable%20Extended%20Logging). These options can only be set globally and not per workspace.
   - `logLevel: "debug"|"info"|"default"|"error"|"fault"`: The level from which one onwards log messages should be written.
   - `privacyLevel: "public"|"private"|"sensitive"`: Whether potentially sensitive information should be redacted. Default is `public`, which redacts potentially sensitive information.

Sources/SKOptions/SourceKitLSPOptions.swift

@@ -219,6 +219,33 @@ public struct SourceKitLSPOptions: Sendable, Codable, Equatable {
     }
   }
 
+  /// User settings controlling code completion.
+  public struct CodeCompletionOptions: Sendable, Codable, Equatable {
+    /// The extent to which a completion action should apply stylistic or
+    /// convenience transformations before passing a result to the client.
+    public enum RewriteLevel: String, Sendable, Codable {
+      case full, never
+    }
+
+    /// Whether trailing closures should be eagerly expanded by SourceKit-LSP
+    /// before being passed to the client.
+    public var rewriteTrailingClosures: RewriteLevel
+
+    public init(rewriteTrailingClosures: RewriteLevel = .full) {
+      self.rewriteTrailingClosures = rewriteTrailingClosures
+    }
+
+    static func merging(
+      base: CodeCompletionOptions,
+      override: CodeCompletionOptions?
+    ) -> CodeCompletionOptions {
+      return CodeCompletionOptions(
+        rewriteTrailingClosures: override?.rewriteTrailingClosures
+          ?? base.rewriteTrailingClosures
+      )
+    }
+  }
+
   public enum BackgroundPreparationMode: String {
     /// Build a target to prepare it
     case build
@@ -271,6 +298,12 @@ public struct SourceKitLSPOptions: Sendable, Codable, Equatable {
     set { logging = newValue }
   }
 
+  private var codeCompletion: CodeCompletionOptions?
+  public var codeCompletionOrDefault: CodeCompletionOptions {
+    get { codeCompletion ?? .init() }
+    set { codeCompletion = newValue }
+  }
+
   /// Default workspace type (buildserver|compdb|swiftpm). Overrides workspace type selection logic.
   public var defaultWorkspaceType: WorkspaceType?
   public var generatedFilesPath: String?
@@ -349,6 +382,7 @@ public struct SourceKitLSPOptions: Sendable, Codable, Equatable {
     clangdOptions: [String]? = nil,
     index: IndexOptions = .init(),
     logging: LoggingOptions = .init(),
+    codeCompletion: CodeCompletionOptions? = nil,
     defaultWorkspaceType: WorkspaceType? = nil,
     generatedFilesPath: String? = nil,
     backgroundIndexing: Bool? = nil,
@@ -365,6 +399,7 @@ public struct SourceKitLSPOptions: Sendable, Codable, Equatable {
     self.clangdOptions = clangdOptions
     self.index = index
     self.logging = logging
+    self.codeCompletion = codeCompletion
     self.generatedFilesPath = generatedFilesPath
     self.defaultWorkspaceType = defaultWorkspaceType
     self.backgroundIndexing = backgroundIndexing
@@ -420,6 +455,10 @@ public struct SourceKitLSPOptions: Sendable, Codable, Equatable {
       clangdOptions: override?.clangdOptions ?? base.clangdOptions,
       index: IndexOptions.merging(base: base.indexOrDefault, override: override?.index),
       logging: LoggingOptions.merging(base: base.loggingOrDefault, override: override?.logging),
+      codeCompletion: CodeCompletionOptions.merging(
+        base: base.codeCompletionOrDefault,
+        override: override?.codeCompletion
+      ),
       defaultWorkspaceType: override?.defaultWorkspaceType ?? base.defaultWorkspaceType,
       generatedFilesPath: override?.generatedFilesPath ?? base.generatedFilesPath,
       backgroundIndexing: override?.backgroundIndexing ?? base.backgroundIndexing,

Sources/SKTestSupport/TestSourceKitLSPClient.swift

@@ -46,6 +46,16 @@ extension SourceKitLSPOptions {
   }
 }
 
+extension SourceKitLSPOptions.CodeCompletionOptions {
+  package static func testDefault(
+    rewriteTrailingClosures: RewriteLevel = .full
+  ) -> SourceKitLSPOptions.CodeCompletionOptions {
+    return SourceKitLSPOptions.CodeCompletionOptions(
+      rewriteTrailingClosures: rewriteTrailingClosures
+    )
+  }
+}
+
 fileprivate struct NotificationTimeoutError: Error, CustomStringConvertible {
   var description: String = "Failed to receive next notification within timeout"
 }

Sources/SourceKitLSP/Swift/CodeCompletionSession.swift

@@ -363,8 +363,13 @@ class CodeCompletionSession {
       let docBrief: String? = value[sourcekitd.keys.docBrief]
       let utf8CodeUnitsToErase: Int = value[sourcekitd.keys.numBytesToErase] ?? 0
 
-      if let closureExpanded = expandClosurePlaceholders(insertText: insertText) {
-        insertText = closureExpanded
+      switch options.codeCompletionOrDefault.rewriteTrailingClosures {
+      case .full:
+        if let closureExpanded = expandClosurePlaceholders(insertText: insertText) {
+          insertText = closureExpanded
+        }
+      case .never:
+        break
       }
 
       let text = rewriteSourceKitPlaceholders(in: insertText, clientSupportsSnippets: clientSupportsSnippets)

Tests/SourceKitLSPTests/SwiftCompletionTests.swift

@@ -13,6 +13,7 @@
 import LanguageServerProtocol
 import SKTestSupport
 import SourceKitLSP
+import SKOptions
 import XCTest
 
 final class SwiftCompletionTests: XCTestCase {
@@ -1036,6 +1037,92 @@ final class SwiftCompletionTests: XCTestCase {
     )
   }
 
+  func testExpandClosuresDisabledByConfig() async throws {
+    let testClient = try await TestSourceKitLSPClient(
+      options: SourceKitLSPOptions(codeCompletion: .testDefault(rewriteTrailingClosures: .never)),
+      capabilities: snippetCapabilities
+    )
+    let uri = DocumentURI(for: .swift)
+    let positions = testClient.openDocument(
+      """
+      struct MyArray {
+          func myMap(_ body: (Int) -> Bool) {}
+      }
+      func test(x: MyArray) {
+          x.1️⃣
+      }
+      """,
+      uri: uri
+    )
+    let completions = try await testClient.send(
+      CompletionRequest(textDocument: TextDocumentIdentifier(uri), position: positions["1️⃣"])
+    )
+    XCTAssertEqual(
+      completions.items.filter { $0.label.contains("myMap") },
+      [
+        CompletionItem(
+          label: "myMap(body: (Int) -> Bool)",
+          kind: .method,
+          detail: "Void",
+          deprecated: false,
+          sortText: nil,
+          filterText: "myMap(:)",
+          insertText: "myMap(${1:(Int) -> Bool})",
+          insertTextFormat: .snippet,
+          textEdit: .textEdit(
+            TextEdit(
+              range: Range(positions["1️⃣"]),
+              newText: "myMap(${1:(Int) -> Bool})"
+            )
+          )
+        )
+      ]
+    )
+  }
+
+  func testExpandMultipleTrailingClosuresDisabledByConfig() async throws {
+    let testClient = try await TestSourceKitLSPClient(
+      options: SourceKitLSPOptions(codeCompletion: .testDefault(rewriteTrailingClosures: .never)),
+      capabilities: snippetCapabilities
+    )
+    let uri = DocumentURI(for: .swift)
+    let positions = testClient.openDocument(
+      """
+      struct MyArray {
+          func myMap(_ body: (Int) -> Bool, second: (Int) -> String) {}
+      }
+      func test(x: MyArray) {
+          x.1️⃣
+      }
+      """,
+      uri: uri
+    )
+    let completions = try await testClient.send(
+      CompletionRequest(textDocument: TextDocumentIdentifier(uri), position: positions["1️⃣"])
+    )
+    XCTAssertEqual(
+      completions.items.filter { $0.label.contains("myMap") },
+      [
+        CompletionItem(
+          label: "myMap(body: (Int) -> Bool, second: (Int) -> String)",
+          kind: .method,
+          detail: "Void",
+          deprecated: false,
+          sortText: nil,
+          filterText: "myMap(:second:)",
+          insertText: "myMap(${1:(Int) -> Bool}, second: ${2:(Int) -> String})",
+          insertTextFormat: .snippet,
+          textEdit: .textEdit(
+            TextEdit(
+              range: Range(positions["1️⃣"]),
+              newText: "myMap(${1:(Int) -> Bool}, second: ${2:(Int) -> String})"
+            )
+          )
+        )
+      ]
+    )
+  }
+
   func testInferIndentationWhenExpandingClosurePlaceholder() async throws {
     let testClient = try await TestSourceKitLSPClient(capabilities: snippetCapabilities)
     let uri = DocumentURI(for: .swift)