Fix issue that caused code completion request to not be cancellable

Author: ahoppen

Sources/SwiftSourceKitPlugin/CodeCompletion/Connection.swift

@@ -113,6 +113,18 @@ final class Connection {
     sourcekitd.ideApi.connection_dispose(impl)
   }
 
+  //// A function that can be called to cancel a request with a request.
+  ///
+  /// This is not a member function on `Connection` so that `CompletionProvider` can store
+  /// this closure in a member and call it even while the `CompletionProvider` actor is busy
+  /// fulfilling a completion request and thus can't access `connection`.
+  var cancellationFunc: @Sendable (RequestHandle) -> Void {
+    nonisolated(unsafe) let impl = self.impl
+    return { [sourcekitd] handle in
+      sourcekitd.ideApi.cancel_request(impl, handle.handle)
+    }
+  }
+
   func openDocument(path: String, contents: String, compilerArguments: [String]? = nil) {
     if documents[path] != nil {
       logger.error("Document at '\(path)' is already open")
@@ -219,10 +231,6 @@ final class Connection {
     )
   }
 
-  func cancel(handle: RequestHandle) {
-    sourcekitd.ideApi.cancel_request(impl, handle.handle)
-  }
-
   func markCachedCompilerInstanceShouldBeInvalidated() {
     sourcekitd.ideApi.connection_mark_cached_compiler_instance_should_be_invalidated(impl, nil)
   }

Sources/SwiftSourceKitPlugin/CompletionProvider.swift

@@ -86,6 +86,9 @@ actor CompletionProvider {
 
   private let connection: Connection
 
+  /// See `Connection.cancellationFunc`
+  private nonisolated let cancel: @Sendable (RequestHandle) -> Void
+
   /// The XPC custom buffer kind for `CompletionResultsArray`
   private let completionResultsBufferKind: UInt64
 
@@ -101,17 +104,12 @@ actor CompletionProvider {
       opaqueIDEInspectionInstance: opaqueIDEInspectionInstance?.value,
       sourcekitd: sourcekitd
     )
+    self.cancel = connection.cancellationFunc
     self.completionResultsBufferKind = completionResultsBufferKind
   }
 
   nonisolated func cancel(handle: RequestHandle) {
-    Task {
-      await self.cancelImpl(handle: handle)
-    }
-  }
-
-  private func cancelImpl(handle: RequestHandle) {
-    connection.cancel(handle: handle)
+    self.cancel(handle)
   }
 
   func handleDocumentOpen(_ request: SKDRequestDictionaryReader) {