fix(functions): invalidate URLSession in streamed response

Sources/Functions/FunctionsClient.swift

@@ -272,6 +272,13 @@ public final class FunctionsClient: Sendable {
     _ functionName: String,
     options invokeOptions: FunctionInvokeOptions = .init()
   ) -> AsyncThrowingStream<Data, any Error> {
+    streamResponse(functionName, options: invokeOptions).stream
+  }
+
+  func streamResponse(
+    _ functionName: String,
+    options invokeOptions: FunctionInvokeOptions
+  ) -> (stream: AsyncThrowingStream<Data, any Error>, delegate: StreamResponseDelegate) {
     let (stream, continuation) = AsyncThrowingStream<Data, any Error>.makeStream()
     let delegate = StreamResponseDelegate(continuation: continuation)
 
@@ -284,13 +291,10 @@ public final class FunctionsClient: Sendable {
     task.resume()
 
     continuation.onTermination = { _ in
-      task.cancel()
-
-      // Hold a strong reference to delegate until continuation terminates.
-      _ = delegate
+      session.invalidateAndCancel()
     }
 
-    return stream
+    return (stream, delegate)
   }
 
   private func buildRequest(functionName: String, options: FunctionInvokeOptions)

Tests/FunctionsTests/FunctionsClientTests.swift

@@ -566,4 +566,32 @@ struct FunctionsClientTests {
     } catch FunctionsError.relayError {
     }
   }
+
+  @Test
+  func invokeWithStreamedResponseInvalidatesSession() async throws {
+    let sut = makeSUT()
+
+    Mock(
+      url: url.appendingPathComponent("stream"),
+      statusCode: 200,
+      data: [.post: Data("hello world".utf8)]
+    )
+    .register()
+
+    weak var weakDelegate: StreamResponseDelegate?
+
+    do {
+      let (stream, delegate) = sut.streamResponse("stream", options: FunctionInvokeOptions())
+      weakDelegate = delegate
+      for try await _ in stream {}
+    }
+
+    // URLSession releases its delegate asynchronously after invalidation.
+    let deadline = Date().addingTimeInterval(5)
+    while weakDelegate != nil, Date() < deadline {
+      try await Task.sleep(nanoseconds: 10_000_000)
+    }
+
+    #expect(weakDelegate == nil, "URLSession was not invalidated; its delegate leaked")
+  }
 }