Honor receive message completion

Sources/NWWebSocket/Model/Client/NWWebSocket.swift

@@ -188,7 +188,7 @@ open class NWWebSocket: WebSocketConnection {
         guard !isListening else { return }
         isListening = true
 
-        connection?.receiveMessage { [weak self] (data, context, _, error) in
+        connection?.receiveMessage { [weak self] (data, context, isComplete, error) in
             guard let self = self else {
                 return
             }
@@ -198,7 +198,11 @@ open class NWWebSocket: WebSocketConnection {
                 return
             }
 
-            if let data = data, !data.isEmpty, let context = context {
+            if Self.shouldDeliverReceivedMessage(
+                data: data,
+                context: context,
+                isComplete: isComplete
+            ), let data = data, let context = context {
                 self.receiveMessage(data: data, context: context)
             }
 
@@ -212,6 +216,15 @@ open class NWWebSocket: WebSocketConnection {
         }
     }
 
+    /// Return `true` only for a complete message that contains data and metadata.
+    internal static func shouldDeliverReceivedMessage(
+        data: Data?,
+        context: NWConnection.ContentContext?,
+        isComplete: Bool
+    ) -> Bool {
+        isComplete && data?.isEmpty == false && context != nil
+    }
+
     /// Ping the WebSocket periodically.
     /// - Parameter interval: The `TimeInterval` (in seconds) with which to ping the server.
     open func ping(interval: TimeInterval) {

Tests/NWWebSocketTests/ReceiveCompletionTests.swift

@@ -0,0 +1,54 @@
+import Foundation
+import Network
+@testable import NWWebSocket
+import XCTest
+
+final class ReceiveCompletionTests: XCTestCase {
+    func testCompleteMessageIsDelivered() {
+        XCTAssertTrue(
+            NWWebSocket.shouldDeliverReceivedMessage(
+                data: Data("{}".utf8),
+                context: textContext,
+                isComplete: true
+            )
+        )
+    }
+
+    func testIncompleteMessageIsNotDelivered() {
+        XCTAssertFalse(
+            NWWebSocket.shouldDeliverReceivedMessage(
+                data: Data("{\"partial\":".utf8),
+                context: textContext,
+                isComplete: false
+            )
+        )
+    }
+
+    func testEmptyMessageIsNotDelivered() {
+        XCTAssertFalse(
+            NWWebSocket.shouldDeliverReceivedMessage(
+                data: Data(),
+                context: textContext,
+                isComplete: true
+            )
+        )
+    }
+
+    func testMessageWithoutContextIsNotDelivered() {
+        XCTAssertFalse(
+            NWWebSocket.shouldDeliverReceivedMessage(
+                data: Data("{}".utf8),
+                context: nil,
+                isComplete: true
+            )
+        )
+    }
+
+    private var textContext: NWConnection.ContentContext {
+        let metadata = NWProtocolWebSocket.Metadata(opcode: .text)
+        return NWConnection.ContentContext(
+            identifier: "test-text-message",
+            metadata: [metadata]
+        )
+    }
+}