fix: support CRLF SSE frame parsing (#223)

Author: sz9751210

src/cli/transports/SSETransport.ts

@@ -63,19 +63,29 @@ export function parseSSEFrames(buffer: string): {
   const frames: SSEFrame[] = []
   let pos = 0
 
-  // SSE frames are delimited by double newlines
-  let idx: number
-  while ((idx = buffer.indexOf('\n\n', pos)) !== -1) {
-    const rawFrame = buffer.slice(pos, idx)
-    pos = idx + 2
+  // SSE frames are delimited by an empty line. Support LF and CRLF streams.
+  const frameDelimiter = /\r?\n\r?\n/g
+  frameDelimiter.lastIndex = pos
+
+  let delimiterMatch: RegExpExecArray | null
+  while ((delimiterMatch = frameDelimiter.exec(buffer)) !== null) {
+    const frameEnd = delimiterMatch.index
+    const rawFrame = buffer.slice(pos, frameEnd)
+    pos = frameEnd + delimiterMatch[0].length
 
     // Skip empty frames
     if (!rawFrame.trim()) continue
 
     const frame: SSEFrame = {}
     let isComment = false
 
-    for (const line of rawFrame.split('\n')) {
+    for (const rawLine of rawFrame.split('\n')) {
+      // Normalize CRLF lines in mixed-line-ending streams.
+      const line =
+        rawLine[rawLine.length - 1] === '\r'
+          ? rawLine.slice(0, -1)
+          : rawLine
+
       if (line.startsWith(':')) {
         // SSE comment (e.g., `:keepalive`)
         isComment = true

src/cli/transports/__tests__/SSETransport.test.ts

@@ -0,0 +1,49 @@
+import { describe, expect, test } from 'bun:test'
+import { parseSSEFrames } from '../SSETransport.js'
+
+describe('parseSSEFrames', () => {
+  test('parses LF-delimited frames', () => {
+    const input = 'event: client_event\ndata: {"ok":true}\n\n'
+    const { frames, remaining } = parseSSEFrames(input)
+
+    expect(remaining).toBe('')
+    expect(frames).toEqual([
+      {
+        event: 'client_event',
+        data: '{"ok":true}',
+      },
+    ])
+  })
+
+  test('parses CRLF-delimited frames and strips trailing carriage returns', () => {
+    const input =
+      'event: client_event\r\ndata: {"ok":true}\r\nid: 7\r\n\r\nevent: keepalive\r\ndata: ping\r\n\r\n'
+    const { frames, remaining } = parseSSEFrames(input)
+
+    expect(remaining).toBe('')
+    expect(frames).toEqual([
+      {
+        event: 'client_event',
+        data: '{"ok":true}',
+        id: '7',
+      },
+      {
+        event: 'keepalive',
+        data: 'ping',
+      },
+    ])
+  })
+
+  test('keeps incomplete trailing frame in remaining buffer for CRLF streams', () => {
+    const input = 'event: client_event\r\ndata: {"ok":true}\r\n\r\ndata: {"tail":1}\r\n'
+    const { frames, remaining } = parseSSEFrames(input)
+
+    expect(frames).toEqual([
+      {
+        event: 'client_event',
+        data: '{"ok":true}',
+      },
+    ])
+    expect(remaining).toBe('data: {"tail":1}\r\n')
+  })
+})