From aced4a009fff72a16b389cf3bf82b9a24d89bcfd Mon Sep 17 00:00:00 2001
From: Ates Goral <ates.goral@shopify.com>
Date: Fri, 6 Oct 2023 16:31:38 -0400
Subject: [PATCH] Handle multi-line data while composing SSE

---
 src/server/event-stream.ts       |  6 +++++-
 test/server/event-stream.test.ts | 14 ++++++++++++--
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/server/event-stream.ts b/src/server/event-stream.ts
index 34b3a49..454c1a0 100644
--- a/src/server/event-stream.ts
+++ b/src/server/event-stream.ts
@@ -39,7 +39,11 @@ export function eventStream(
 
 			function send({ event = "message", data }: SendFunctionArgs) {
 				controller.enqueue(encoder.encode(`event: ${event}\n`));
-				controller.enqueue(encoder.encode(`data: ${data}\n\n`));
+
+				const lines = data.split("\n");
+				const dataLines = lines.map((line) => `data: ${line}`).join("\n");
+
+				controller.enqueue(encoder.encode(`${dataLines}\n\n`));
 			}
 
 			let cleanup = init(send, close);
diff --git a/test/server/event-stream.test.ts b/test/server/event-stream.test.ts
index 0a2b3ad..8537efe 100644
--- a/test/server/event-stream.test.ts
+++ b/test/server/event-stream.test.ts
@@ -28,6 +28,7 @@ describe(eventStream, () => {
 		let controller = new AbortController();
 		let response = eventStream(controller.signal, (send, _) => {
 			send({ data: "hello" });
+			send({ event: "multi-line", data: "hello\nworld" });
 			return () => {};
 		});
 
@@ -36,12 +37,21 @@ describe(eventStream, () => {
 		if (!response.body) throw new Error("Response body is undefined");
 
 		let reader = response.body.getReader();
+		let decoder = new TextDecoder();
 
 		let { value: event } = await reader.read();
-		expect(event).toEqual(new TextEncoder().encode("event: message\n"));
+		expect(decoder.decode(event)).toEqual("event: message\n");
 
 		let { value: data } = await reader.read();
-		expect(data).toEqual(new TextEncoder().encode("data: hello\n\n"));
+		expect(decoder.decode(data)).toEqual("data: hello\n\n");
+
+		let { value: multiLineEvent } = await reader.read();
+		expect(decoder.decode(multiLineEvent)).toEqual("event: multi-line\n");
+
+		let { value: multiLineData } = await reader.read();
+		expect(decoder.decode(multiLineData)).toEqual(
+			"data: hello\ndata: world\n\n",
+		);
 
 		let { done } = await reader.read();
 		expect(done).toBe(true);