fix: edge case when user (or server) sends headers before first event…

… is sent Signed-off-by: Marin Petrunic <[email protected]>
mpetrunic · Jul 25, 2023 · b859f3f · b859f3f
1 parent 470b474
commit b859f3f
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diff --git a/src/plugin.ts b/src/plugin.ts
@@ -34,6 +34,10 @@ export const plugin: FastifyPluginAsync<SsePluginOptions> = async function (
       if (isAsyncIterable(source)) {
         return handleAsyncIterable(this, source);
       } else {
+        if (!this.sseContext?.source) {
+          this.sseContext = { source: pushable<EventMessage>() };
+          handleAsyncIterable(this, this.sseContext.source);
+        }
         this.sseContext.source.push(source);
         return;
       }

diff --git a/test/fastify4/fastify4.spec.ts b/test/fastify4/fastify4.spec.ts
@@ -110,6 +110,27 @@ describe("Fastify - Test SSE plugin", function () {
 
   });
 
+  it("should send event after headers has been sent by user", function (done) {
+    const handler: RouteHandler = async (req, resp): Promise<void> => {
+      resp.header("Content-Type", "text/event-stream");
+      resp.raw.flushHeaders();
+      resp.sse({id: "1", event: "message", data: "Something"});
+      return resp;
+    };
+    getFastifyServer(handler).then((server2) => {
+      const eventsource = getEventSource(server2);
+      eventsource.onmessage = (evt => {
+        expect(evt.data).equal("Something");
+        expect(evt.type).equal("message");
+        expect(evt.lastEventId).equal("1");
+        eventsource.close();
+        server2.close();
+        done();
+      });
+    });
+
+  });
+
   it("should send multiple events", function (done) {
     const eventsource = getEventSource(server);
     source.push({id: "1", event: "message", data: "Something"});