fix(http): handle empty values and multi-line comments in ServerSentEventStream

http/server_sent_event_stream.ts

@@ -37,36 +37,33 @@ function assertHasNoNewline(value: string, varName: string, errPrefix: string) {
  */
 function stringify(message: ServerSentEventMessage): Uint8Array {
   const lines = [];
-  if (message.comment) {
-    assertHasNoNewline(
-      message.comment,
-      "`message.comment`",
-      "Cannot serialize message",
+  if (message.comment !== undefined) {
+    message.comment.split(NEWLINE_REGEXP).forEach((line) =>
+      lines.push(`:${line}`)
     );
-    lines.push(`:${message.comment}`);
   }
-  if (message.event) {
+  if (message.event !== undefined) {
     assertHasNoNewline(
       message.event,
       "`message.event`",
       "Cannot serialize message",
     );
     lines.push(`event:${message.event}`);
   }
-  if (message.data) {
+  if (message.data !== undefined) {
     message.data.split(NEWLINE_REGEXP).forEach((line) =>
       lines.push(`data:${line}`)
     );
   }
-  if (message.id) {
+  if (message.id !== undefined) {
     assertHasNoNewline(
       message.id.toString(),
       "`message.id`",
       "Cannot serialize message",
     );
     lines.push(`id:${message.id}`);
   }
-  if (message.retry) lines.push(`retry:${message.retry}`);
+  if (message.retry !== undefined) lines.push(`retry:${message.retry}`);
   return encoder.encode(lines.join("\n") + "\n\n");
 }
 

http/server_sent_event_stream_test.ts

@@ -58,26 +58,33 @@ Deno.test("ServerSentEventStream enqueues a stringified server-sent event messag
   );
 });
 
-Deno.test("ServerSentEventStream throws if single-line fields contain a newline", async () => {
-  // Comment
-  await assertRejects(
-    async () => await createStream([{ comment: "a\n" }]).getReader().read(),
-    SyntaxError,
-    "`message.comment` cannot contain a newline",
-  );
+Deno.test("ServerSentEventStream serializes multi-line comments", async () => {
+  const stream = createStream([{ comment: "line1\nline2\r\nline3" }]);
+  const result = await Array.fromAsync(stream);
 
-  await assertRejects(
-    async () => await createStream([{ comment: "a\r" }]).getReader().read(),
-    SyntaxError,
-    "`message.comment` cannot contain a newline",
-  );
+  assertEquals(result, [":line1\n:line2\n:line3\n\n"]);
+});
 
-  await assertRejects(
-    async () => await createStream([{ comment: "a\n\r" }]).getReader().read(),
-    SyntaxError,
-    "`message.comment` cannot contain a newline",
-  );
+Deno.test("ServerSentEventStream serializes empty string fields", async () => {
+  const stream = createStream([
+    { comment: "" },
+    { event: "" },
+    { data: "" },
+    { id: 0 },
+    { retry: 0 },
+  ]);
+  const result = await Array.fromAsync(stream);
 
+  assertEquals(result, [
+    ":\n\n",
+    "event:\n\n",
+    "data:\n\n",
+    "id:0\n\n",
+    "retry:0\n\n",
+  ]);
+});
+
+Deno.test("ServerSentEventStream throws if single-line fields contain a newline", async () => {
   // Event
   await assertRejects(
     async () => await createStream([{ event: "a\n" }]).getReader().read(),