v2.0.0

This release improves the performance of parsing the response stream and fixes some corner cases to better match the spec

CHANGELOG.md

@@ -1,5 +1,25 @@
 # CHANGELOG
 
+## 2.0.0
+This release improves the performance of parsing the response stream and fixes some corner cases to better match [the spec](https://html.spec.whatwg.org/multipage/server-sent-events.html#event-stream-interpretation).
+
+### Changed
+- The `id`, `event`, and `data` fields are now initialized to empty strings, per the spec (they were previously `undefined`)
+- The `onmessage` callback is now called for _all_ messages (it was previously triggered only for messages with a `data` field)
+- If a message contains multiple `data` fields, they will be concatenated together into a single string. For example, the following message:
+    ````
+    data: Foo
+    data:Bar
+    data
+    data: Baz
+    ````
+    will result in `{ data: 'Foo\nBar\n\nBaz' }`
+
+- If the `id` field is empty, the `last-event-id` header will no longer be sent on the next reconnect.
+
+### Removed
+- The internal `parseStream` function has been removed. The parse implementation was previously based on async generators, which required a lot of supporting code in both the typescript-generated polyfill as well as the javascript engine. The new implementation is based on simple callbacks, which should be much faster.
+
 ## 1.0.2
 ### Changed
 - Updated examples in readme to fix typos, added more comments.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@microsoft/fetch-event-source",
-  "version": "1.0.2",
+  "version": "2.0.0",
   "description": "A better API for making Event Source requests, with all the features of fetch()",
   "homepage": "https://github.com/Azure/fetch-event-source#readme",
   "bugs": {

src/fetch.ts

@@ -1,8 +1,9 @@
-import { parseStream, EventSourceMessage } from './parse';
+import { EventSourceMessage, getBytes, getLines, getMessages } from './parse';
 
 export const EventStreamContentType = 'text/event-stream';
 
 const DefaultRetryInterval = 1000;
+const LastEventId = 'last-event-id';
 
 export interface FetchEventSourceInit extends RequestInit {
     /**
@@ -96,24 +97,6 @@ export function fetchEventSource(input: RequestInfo, {
             resolve(); // don't waste time constructing/logging errors
         });
 
-        async function parseResponse(response: Response) {
-            for await (const msg of parseStream(response.body)) {
-                // first check for system events:
-                if (msg.id !== undefined) {
-                    // keep track of the last-seen ID and send it back on the next retry:
-                    headers['last-event-id'] = msg.id;
-                }
-
-                if (msg.retry !== undefined) {
-                    retryInterval = msg.retry;
-                }
-
-                if (msg.data !== undefined && onmessage != null) {
-                    onmessage(msg);
-                }
-            }
-        }
-
         const fetch = inputFetch ?? window.fetch;
         const onopen = inputOnOpen ?? defaultOnOpen;
         async function create() {
@@ -126,8 +109,18 @@ export function fetchEventSource(input: RequestInfo, {
                 });
 
                 await onopen(response);
-
-                await parseResponse(response);
+
+                await getBytes(response.body, getLines(getMessages(id => {
+                    if (id) {
+                        // store the id and send it back on the next retry:
+                        headers[LastEventId] = id;
+                    } else {
+                        // don't send the last-event-id header anymore:
+                        delete headers[LastEventId];
+                    }
+                }, retry => {
+                    retryInterval = retry;
+                }, onmessage)));
 
                 onclose?.();
                 dispose();

src/index.ts

@@ -1,2 +1,2 @@
 export { fetchEventSource, FetchEventSourceInit, EventStreamContentType } from './fetch';
-export { parseStream, EventSourceMessage } from './parse';
+export { EventSourceMessage } from './parse';