feat: support environments without TextDecoderStream support

README.md

@@ -35,7 +35,7 @@ npm install --save eventsource-client
 - Firefox >= 105
 - Edge >= 79
 
-Basically, any environment that supports the [ReadableStream](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream) (with [pipeThrough](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream/pipeThrough) support) and the [TextDecoderStream](https://developer.mozilla.org/en-US/docs/Web/API/TextDecoderStream) APIs.
+Basically, any environment that supports the [ReadableStream](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream) and the [TextDecoder](https://developer.mozilla.org/en-US/docs/Web/API/TextDecoder) APIs.
 
 ## Usage (async iterator)
 
@@ -96,7 +96,7 @@ es.close()
 - [ ] Configurable stalled connection detection (eg no data)
 - [ ] Configurable reconnection policy
 - [ ] Deno support/tests
-- [ ] Bun support/tests (blocked: no `TextDecoderStream` support)
+- [ ] Bun support/tests
 - [ ] Consider legacy build
 
 ## License

src/client.ts

@@ -188,19 +188,21 @@ export function createEventSource(
     // Ensure that the response stream is a web stream
     // @todo Figure out a way to make this work without casting
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    const bodyStream = getStream(body as any)
+    const stream = getStream(body as any)
+    const decoder = new TextDecoder()
 
-    // EventSources are always UTF-8 per spec
-    const stream = bodyStream.pipeThrough<string>(new TextDecoderStream())
     const reader = stream.getReader()
     let open = true
 
     readyState = OPEN
 
     do {
       const {done, value} = await reader.read()
+      if (value) {
+        parser.feed(decoder.decode(value, {stream: !done}))
+      }
+
       if (!done) {
-        parser.feed(value)
         continue
       }
 

test/fixtures.ts

@@ -0,0 +1,4 @@
+export const unicodeLines = [
+  '🦄 are cool. 🐾 in the snow. Allyson Felix, 🏃🏽‍♀️ 🥇 2012 London!',
+  'Espen ♥ Kokos',
+]

test/server.ts

@@ -5,6 +5,8 @@ import {resolve as resolvePath} from 'node:path'
 
 import esbuild from 'esbuild'
 
+import {unicodeLines} from './fixtures'
+
 export function getServer(port: number): Promise<Server> {
   return new Promise((resolve, reject) => {
     const server = createServer(onRequest)
@@ -14,6 +16,11 @@ export function getServer(port: number): Promise<Server> {
 }
 
 function onRequest(req: IncomingMessage, res: ServerResponse) {
+  // Disable Nagle's algorithm for testing
+  if (res.socket) {
+    res.socket.setNoDelay(true)
+  }
+
   switch (req.url) {
     // Server-Sent Event endpoints
     case '/':
@@ -36,6 +43,8 @@ function onRequest(req: IncomingMessage, res: ServerResponse) {
       return writeStalledConnection(req, res)
     case '/trickle':
       return writeTricklingConnection(req, res)
+    case '/unicode':
+      return writeUnicode(req, res)
 
     // Browser test endpoints (HTML/JS)
     case '/browser-test':
@@ -170,6 +179,49 @@ async function writeStalledConnection(req: IncomingMessage, res: ServerResponse)
   // Intentionally not closing on first-connect that never sends data after welcome
 }
 
+async function writeUnicode(_req: IncomingMessage, res: ServerResponse) {
+  res.writeHead(200, {
+    'Content-Type': 'text/event-stream',
+    'Cache-Control': 'no-cache',
+    Connection: 'keep-alive',
+  })
+
+  res.write(
+    formatEvent({
+      event: 'welcome',
+      data: 'Connected - I will now send some chonks (cuter chunks) with unicode',
+    }),
+  )
+
+  res.write(
+    formatEvent({
+      event: 'unicode',
+      data: unicodeLines[0],
+    }),
+  )
+
+  await delay(100)
+
+  // Start of a valid SSE chunk
+  res.write('event: unicode\ndata: ')
+
+  // Write "Espen ❤️ Kokos" in two halves:
+  // 1st: Espen � [..., 226, 153]
+  // 2st: � Kokos [165, 32, ...]
+  res.write(new Uint8Array([69, 115, 112, 101, 110, 32, 226, 153]))
+
+  // Give time to the client to process the first half
+  await delay(1000)
+
+  res.write(new Uint8Array([165, 32, 75, 111, 107, 111, 115]))
+
+  // Closing end of packet
+  res.write('\n\n\n\n')
+
+  res.write(formatEvent({event: 'disconnect', data: 'Thanks for listening'}))
+  res.end()
+}
+
 async function writeTricklingConnection(_req: IncomingMessage, res: ServerResponse) {
   res.writeHead(200, {
     'Content-Type': 'text/event-stream',

test/tests.ts

@@ -1,5 +1,6 @@
 import {CLOSED, CONNECTING, OPEN} from '../src/constants'
-import type {createEventSource as CreateEventSourceFn} from '../src/default'
+import type {createEventSource as CreateEventSourceFn, EventSourceMessage} from '../src/default'
+import {unicodeLines} from './fixtures'
 import {deferClose, expect, getCallCounter} from './helpers'
 import type {TestRunner} from './waffletest'
 
@@ -41,6 +42,31 @@ export function registerTests(options: {
     await deferClose(es)
   })
 
+  test('can handle unicode data correctly', async () => {
+    const onMessage = getCallCounter()
+    const es = createEventSource({
+      url: new URL(`${baseUrl}:${port}/unicode`),
+      fetch,
+      onMessage,
+    })
+
+    const messages: EventSourceMessage[] = []
+    for await (const event of es) {
+      if (event.event === 'unicode') {
+        messages.push(event)
+      }
+
+      if (messages.length === 2) {
+        break
+      }
+    }
+
+    expect(messages[0].data).toBe(unicodeLines[0])
+    expect(messages[1].data).toBe(unicodeLines[1])
+
+    await deferClose(es)
+  })
+
   test('will reconnect with last received message id if server disconnects', async () => {
     const onMessage = getCallCounter()
     const onDisconnect = getCallCounter()