fix(sse): emit retry feild when retry is 0 (#5135)

Author: yusukebe

src/helper/streaming/sse.test.tsx

@@ -132,6 +132,28 @@ describe('SSE Streaming helper', () => {
     expect(decodedValue).toContain(expectedRetryValue)
   })
 
+  it('Should accept retry: 0 and not skip it', async () => {
+    const res = streamSSE(c, async (stream) => {
+      await stream.writeSSE({
+        data: 'This is a test message',
+        retry: 0,
+      })
+    })
+
+    expect(res).not.toBeNull()
+    expect(res.status).toBe(200)
+
+    if (!res.body) {
+      throw new Error('Body is null')
+    }
+    const reader = res.body.getReader()
+    const decoder = new TextDecoder()
+    const { value } = await reader.read()
+    const decodedValue = decoder.decode(value)
+
+    expect(decodedValue).toContain('retry: 0\n\n')
+  })
+
   it('Check stream Response if error occurred', async () => {
     const onError = vi.fn()
     const res = streamSSE(

src/helper/streaming/sse.ts

@@ -24,8 +24,9 @@ export class SSEStreamingApi extends StreamingApi {
       })
       .join('\n')
 
-    for (const key of ['event', 'id', 'retry'] as (keyof SSEMessage)[]) {
-      if (message[key] && /[\r\n]/.test(message[key] as string)) {
+    for (const key of ['event', 'id'] as const) {
+      const value = message[key]
+      if (value && /[\r\n]/.test(value)) {
         throw new Error(`${key} must not contain "\\r" or "\\n"`)
       }
     }
@@ -35,7 +36,7 @@ export class SSEStreamingApi extends StreamingApi {
         message.event && `event: ${message.event}`,
         dataLines,
         message.id && `id: ${message.id}`,
-        message.retry && `retry: ${message.retry}`,
+        message.retry !== undefined && `retry: ${message.retry}`,
       ]
         .filter(Boolean)
         .join('\n') + '\n\n'