fix(room-share): count braces outside JSON strings only

changelog.d/2447-room-share-brace-in-text.fixed.md

@@ -0,0 +1 @@
+A chat line that carries a brace — `if (x) { y()` or a lone `}` — reaches the room again instead of being dropped: the room-share parser counts braces outside JSON strings only, so one unbalanced brace no longer ends the envelope early.

core/src/shared/room-share.js

@@ -255,11 +255,22 @@ export function parseRoomShare(text) {
   if (at < 0) return undefined
   const start = raw.indexOf('{', at)
   if (start < 0) return undefined
+  // #2447: braces inside a JSON string are the sender's characters, not structure. One unbalanced
+  // brace in a chat line used to close the envelope early and drop the whole line.
   let depth = 0
   let end = -1
+  let inString = false
+  let escaped = false
   for (let i = start; i < raw.length; i += 1) {
     const ch = raw[i]
-    if (ch === '{') depth += 1
+    if (inString) {
+      if (escaped) escaped = false
+      else if (ch === '\\') escaped = true
+      else if (ch === '"') inString = false
+      continue
+    }
+    if (ch === '"') inString = true
+    else if (ch === '{') depth += 1
     else if (ch === '}') {
       depth -= 1
       if (depth === 0) { end = i; break }

core/test/room-share-brace-in-text.test.js

@@ -0,0 +1,34 @@
+// A brace in a chat line is a character someone typed, not structure (#2447): `parseRoomShare`
+// finds the end of the JSON envelope by counting braces, and it must not count the ones inside the
+// strings `encodeRoomShare` writes — otherwise a single unbalanced brace drops the whole line.
+import assert from 'node:assert/strict'
+import { test } from 'node:test'
+import { encodeRoomShare, parseRoomShare } from '../src/shared/room-share.js'
+
+const line = (text) => encodeRoomShare({ op: 'line', roomId: 'r1', seq: 7, who: 'Alice', text })
+
+test('an open brace in a line does not end the envelope early', () => {
+  const text = 'if (x) { y()'
+  const parsed = parseRoomShare(line(text))
+  assert.ok(parsed, 'the envelope was dropped')
+  assert.equal(parsed.text, text)
+})
+
+test('a close brace in a line does not end the envelope early', () => {
+  const text = 'so the closing brace is }'
+  const parsed = parseRoomShare(line(text))
+  assert.ok(parsed, 'the envelope was dropped')
+  assert.equal(parsed.text, text)
+})
+
+test('a brace inside a quoted word, and an escaped quote, both stay text', () => {
+  const text = 'he said "{" and then "}" and \\ back'
+  const parsed = parseRoomShare(line(text))
+  assert.ok(parsed, 'the envelope was dropped')
+  assert.equal(parsed.text, text)
+})
+
+test('an envelope that really is cut short is still refused (control)', () => {
+  const text = line('hello there')
+  assert.equal(parseRoomShare(text.slice(0, text.length - 3)), undefined)
+})

patches/ds-bot/files/src/shared/room-share.js

@@ -255,11 +255,22 @@ export function parseRoomShare(text) {
   if (at < 0) return undefined
   const start = raw.indexOf('{', at)
   if (start < 0) return undefined
+  // #2447: braces inside a JSON string are the sender's characters, not structure. One unbalanced
+  // brace in a chat line used to close the envelope early and drop the whole line.
   let depth = 0
   let end = -1
+  let inString = false
+  let escaped = false
   for (let i = start; i < raw.length; i += 1) {
     const ch = raw[i]
-    if (ch === '{') depth += 1
+    if (inString) {
+      if (escaped) escaped = false
+      else if (ch === '\\') escaped = true
+      else if (ch === '"') inString = false
+      continue
+    }
+    if (ch === '"') inString = true
+    else if (ch === '{') depth += 1
     else if (ch === '}') {
       depth -= 1
       if (depth === 0) { end = i; break }

patches/ds-bot/files/test/room-share-brace-in-text.test.js

@@ -0,0 +1,34 @@
+// A brace in a chat line is a character someone typed, not structure (#2447): `parseRoomShare`
+// finds the end of the JSON envelope by counting braces, and it must not count the ones inside the
+// strings `encodeRoomShare` writes — otherwise a single unbalanced brace drops the whole line.
+import assert from 'node:assert/strict'
+import { test } from 'node:test'
+import { encodeRoomShare, parseRoomShare } from '../src/shared/room-share.js'
+
+const line = (text) => encodeRoomShare({ op: 'line', roomId: 'r1', seq: 7, who: 'Alice', text })
+
+test('an open brace in a line does not end the envelope early', () => {
+  const text = 'if (x) { y()'
+  const parsed = parseRoomShare(line(text))
+  assert.ok(parsed, 'the envelope was dropped')
+  assert.equal(parsed.text, text)
+})
+
+test('a close brace in a line does not end the envelope early', () => {
+  const text = 'so the closing brace is }'
+  const parsed = parseRoomShare(line(text))
+  assert.ok(parsed, 'the envelope was dropped')
+  assert.equal(parsed.text, text)
+})
+
+test('a brace inside a quoted word, and an escaped quote, both stay text', () => {
+  const text = 'he said "{" and then "}" and \\ back'
+  const parsed = parseRoomShare(line(text))
+  assert.ok(parsed, 'the envelope was dropped')
+  assert.equal(parsed.text, text)
+})
+
+test('an envelope that really is cut short is still refused (control)', () => {
+  const text = line('hello there')
+  assert.equal(parseRoomShare(text.slice(0, text.length - 3)), undefined)
+})