fix(eventsource): handle empty event fields

lib/web/eventsource/eventsource-stream.js

@@ -309,9 +309,7 @@ class EventSourceStream extends Transform {
     if (isFieldName(line, fieldLength, EVENT)) {
       const value = line.toString('utf8', valueStart)
 
-      if (value.length > 0) {
-        event.event = value
-      }
+      event.event = value
     }
   }
 

test/eventsource/eventsource-message.js

@@ -86,6 +86,33 @@ describe('EventSource - message', () => {
     })
   })
 
+  test('Should use the default message type when an empty event field replaces a custom type', async (t) => {
+    t.plan(3)
+
+    const server = http.createServer({ joinDuplicateHeaders: true }, (_req, res) => {
+      res.writeHead(200, 'OK', { 'Content-Type': 'text/event-stream' })
+      res.end('event: custom\nevent:\ndata: payload\n\n')
+    })
+
+    await once(server.listen(0), 'listening')
+    const port = server.address().port
+    const eventSourceInstance = new EventSource(`http://localhost:${port}`)
+
+    t.after(async () => {
+      eventSourceInstance.close()
+      await new Promise(resolve => server.close(resolve))
+    })
+
+    const received = await Promise.race([
+      once(eventSourceInstance, 'message').then(([event]) => ({ listener: 'message', event })),
+      once(eventSourceInstance, 'custom').then(([event]) => ({ listener: 'custom', event }))
+    ])
+
+    t.assert.strictEqual(received.listener, 'message')
+    t.assert.strictEqual(received.event.type, 'message')
+    t.assert.strictEqual(received.event.data, 'payload')
+  })
+
   test('Should emit a message event if data is provided', (t, done) => {
     t.plan(1)
 

test/eventsource/eventsource-stream-parse-line.js

@@ -258,23 +258,19 @@ describe('EventSourceStream - parseLine', () => {
     t.assert.strictEqual(event.retry, undefined)
   })
 
-  test('empty event', (t) => {
+  test('empty event replaces previous event type', (t) => {
     const stream = new EventSourceStream({
       eventSourceSettings: {
         ...defaultEventSourceSettings
       }
     })
 
     const event = {}
-    'event: \ndata:data'.split('\n').forEach((line) => {
-      stream.parseLine(Buffer.from(line, 'utf8'), event)
-    })
 
-    t.assert.strictEqual(typeof event, 'object')
-    t.assert.strictEqual(Object.keys(event).length, 1)
-    t.assert.strictEqual(event.data, 'data')
-    t.assert.strictEqual(event.id, undefined)
-    t.assert.strictEqual(event.event, undefined)
-    t.assert.strictEqual(event.retry, undefined)
+    stream.parseLine(Buffer.from('event: custom', 'utf8'), event)
+    t.assert.strictEqual(event.event, 'custom')
+
+    stream.parseLine(Buffer.from('event: ', 'utf8'), event)
+    t.assert.strictEqual(event.event, '')
   })
 })