feat: EventSource can be configured with reconnectionTime (#4260)

Uzlopak · web-flow · commit b49a29ab88a6 · 2025-08-11T12:43:00.000-04:00
* feat: EventSource can be configured with node.reconnectionTime, deprecate dispatcher attribute on top level

* no need for optional chaining

* improve test
diff --git a/lib/web/eventsource/eventsource.js b/lib/web/eventsource/eventsource.js
@@ -124,10 +124,10 @@ class EventSource extends EventTarget {
     url = webidl.converters.USVString(url)
     eventSourceInitDict = webidl.converters.EventSourceInitDict(eventSourceInitDict, prefix, 'eventSourceInitDict')
 
-    this.#dispatcher = eventSourceInitDict.dispatcher
+    this.#dispatcher = eventSourceInitDict.node.dispatcher || eventSourceInitDict.dispatcher
     this.#state = {
       lastEventId: '',
-      reconnectionTime: defaultReconnectionTime
+      reconnectionTime: eventSourceInitDict.node.reconnectionTime
     }
 
     // 2. Let settings be ev's relevant settings object.
@@ -472,6 +472,21 @@ webidl.converters.EventSourceInitDict = webidl.dictionaryConverter([
   {
     key: 'dispatcher', // undici only
     converter: webidl.converters.any
+  },
+  {
+    key: 'node', // undici only
+    converter: webidl.dictionaryConverter([
+      {
+        key: 'reconnectionTime',
+        converter: webidl.converters['unsigned long'],
+        defaultValue: () => defaultReconnectionTime
+      },
+      {
+        key: 'dispatcher',
+        converter: webidl.converters.any
+      }
+    ]),
+    defaultValue: () => ({})
   }
 ])
 
diff --git a/test/eventsource/eventsource-connect.js b/test/eventsource/eventsource-connect.js
@@ -4,7 +4,7 @@ const assert = require('node:assert')
 const events = require('node:events')
 const http = require('node:http')
 const { test, describe } = require('node:test')
-const { EventSource } = require('../../lib/web/eventsource/eventsource')
+const { EventSource, defaultReconnectionTime } = require('../../lib/web/eventsource/eventsource')
 const { randomInt } = require('node:crypto')
 
 describe('EventSource - sending correct request headers', () => {
@@ -184,6 +184,7 @@ describe('EventSource - received response must have content-type to be text/even
   })
 
   test('should try to connect again if server is unreachable', async () => {
+    const reconnectionTime = defaultReconnectionTime
     const domain = 'bad.n' + randomInt(1e10).toString(36) + '.proxy'
 
     const eventSourceInstance = new EventSource(`http://${domain}`)
@@ -192,11 +193,39 @@ describe('EventSource - received response must have content-type to be text/even
     eventSourceInstance.onerror = (error) => {
       onerrorCalls.push(error)
     }
+    await events.once(eventSourceInstance, 'error')
 
-    await new Promise(resolve => setTimeout(resolve, 8000))
+    const start = Date.now()
+    await events.once(eventSourceInstance, 'error')
+    await events.once(eventSourceInstance, 'error')
+    await events.once(eventSourceInstance, 'error')
+    const end = Date.now()
 
     eventSourceInstance.close()
 
-    assert.strictEqual(onerrorCalls.length, 3)
+    assert.strictEqual(end - start < (3.5 * reconnectionTime), true)
+  })
+
+  test('should try to connect again if server is unreachable', async () => {
+    const reconnectionTime = 500
+
+    const domain = 'bad.n' + randomInt(1e10).toString(36) + '.proxy'
+
+    const eventSourceInstance = new EventSource(`http://${domain}`, {
+      node: {
+        reconnectionTime
+      }
+    })
+    await events.once(eventSourceInstance, 'error')
+
+    const start = Date.now()
+    await events.once(eventSourceInstance, 'error')
+    await events.once(eventSourceInstance, 'error')
+    await events.once(eventSourceInstance, 'error')
+    const end = Date.now()
+
+    eventSourceInstance.close()
+
+    assert.strictEqual(end - start < (3.5 * reconnectionTime), true)
   })
 })
diff --git a/test/eventsource/eventsource-custom-dispatcher.js b/test/eventsource/eventsource-custom-dispatcher.js
@@ -36,3 +36,36 @@ test('EventSource allows setting custom dispatcher.', async (t) => {
 
   await completed
 })
+
+test('EventSource allows setting custom dispatcher in EventSourceDict.', async (t) => {
+  const { completed, deepStrictEqual } = tspl(t, { plan: 1 })
+
+  const server = createServer({ joinDuplicateHeaders: true }, async (req, res) => {
+    res.writeHead(200, 'OK', { 'Content-Type': 'text/event-stream' })
+    deepStrictEqual(req.headers['x-customer-header'], 'hello world')
+
+    res.end()
+  }).listen(0)
+
+  t.after(() => {
+    server.close()
+    eventSourceInstance.close()
+  })
+
+  await once(server, 'listening')
+
+  class CustomHeaderAgent extends Agent {
+    dispatch (opts) {
+      opts.headers['x-customer-header'] = 'hello world'
+      return super.dispatch(...arguments)
+    }
+  }
+
+  const eventSourceInstance = new EventSource(`http://localhost:${server.address().port}`, {
+    node: {
+      dispatcher: new CustomHeaderAgent()
+    }
+  })
+
+  await completed
+})
diff --git a/types/eventsource.d.ts b/types/eventsource.d.ts
@@ -56,6 +56,11 @@ export declare const EventSource: {
 }
 
 interface EventSourceInit {
-  withCredentials?: boolean,
+  withCredentials?: boolean
+  // @deprecated use `node.dispatcher` instead
   dispatcher?: Dispatcher
+  node?: {
+    dispatcher?: Dispatcher
+    reconnectionTime?: number
+  }
 }

Original file line number	Diff line number	Diff line change
`@@ -56,6 +56,11 @@ export declare const EventSource: {`
`56`	`56`	`}`
`57`	`57`
`58`	`58`	`interface EventSourceInit {`
`59`		`- withCredentials?: boolean,`
	`59`	`+ withCredentials?: boolean`
	`60`	+ // @deprecated use `node.dispatcher` instead
`60`	`61`	`dispatcher?: Dispatcher`
	`62`	`+ node?: {`
	`63`	`+ dispatcher?: Dispatcher`
	`64`	`+ reconnectionTime?: number`
	`65`	`+ }`
`61`	`66`	`}`