From 29e16bdd42192f09e0b8c28538abc13243527920 Mon Sep 17 00:00:00 2001
From: Eric Bailey <git@esb.lol>
Date: Fri, 28 Aug 2026 14:52:49 -0500
Subject: [PATCH] Harden RTL language detection

---
 package.json                           |  2 +-
 src/lib/strings/__tests__/bidi.test.ts |  7 +++++++
 src/lib/strings/bidi.ts                | 15 +++++++++++----
 3 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/package.json b/package.json
index 32b58d9840..1d87a848b7 100644
--- a/package.json
+++ b/package.json
@@ -340,7 +340,7 @@
       "^cborg$": "<rootDir>/node_modules/cborg/cborg.js"
     },
     "transformIgnorePatterns": [
-      "node_modules/(?!((jest-)?react-native|@react-native(-community)?)|expo(nent)?|@expo(nent)?/.*|@expo-google-fonts/.*|react-navigation|nanoid|@react-navigation/.*|@unimodules/.*|unimodules|sentry-expo|native-base|normalize-url|react-native-svg|@sentry/.*|sentry-expo|bcp-47-match|@atproto/.*|@bsky/sdk|tlds|multiformats|uint8arrays|@ipld/.*|cborg|await-lock)"
+      "node_modules/(?!((jest-)?react-native|@react-native(-community)?)|expo(nent)?|@expo(nent)?/.*|@expo-google-fonts/.*|react-navigation|nanoid|@react-navigation/.*|@unimodules/.*|unimodules|sentry-expo|native-base|normalize-url|react-native-svg|@sentry/.*|sentry-expo|bcp-47-match|@formatjs/.*|@formatjs_generated/.*|@atproto/.*|@bsky/sdk|tlds|multiformats|uint8arrays|@ipld/.*|cborg|await-lock)"
     ],
     "modulePathIgnorePatterns": [
       "__tests__/.*/__mocks__",
diff --git a/src/lib/strings/__tests__/bidi.test.ts b/src/lib/strings/__tests__/bidi.test.ts
index 3be7cb3b60..0e744e4cf2 100644
--- a/src/lib/strings/__tests__/bidi.test.ts
+++ b/src/lib/strings/__tests__/bidi.test.ts
@@ -1,3 +1,5 @@
+import '@formatjs/intl-locale/polyfill-force.js'
+
 import {describe, expect, it, jest} from '@jest/globals'
 
 /*
@@ -33,6 +35,11 @@ describe('forceLTR', () => {
 })
 
 describe('isRTL', () => {
+  it('uses the Intl.Locale implementation forced in production', () => {
+    expect(Intl.Locale).toHaveProperty('polyfilled', true)
+    expect(Intl.Locale.prototype).toHaveProperty('getTextInfo')
+  })
+
   it('recognizes right-to-left languages and scripts', () => {
     expect(isRTL('he')).toBe(true)
     expect(isRTL('ar')).toBe(true)
diff --git a/src/lib/strings/bidi.ts b/src/lib/strings/bidi.ts
index 273336ab94..7a3d0061ad 100644
--- a/src/lib/strings/bidi.ts
+++ b/src/lib/strings/bidi.ts
@@ -2,6 +2,7 @@ import {IS_WEB} from '#/env'
 
 const LEFT_TO_RIGHT_EMBEDDING = '\u202A'
 const POP_DIRECTIONAL_FORMATTING = '\u202C'
+const languageDirectionCache = new Map<string, boolean>()
 
 /*
  * Force LTR directionality in a string.
@@ -24,10 +25,16 @@ export function forceLTR(str: string) {
 export function isRTL(language: string | undefined) {
   if (!language) return false
 
+  const cached = languageDirectionCache.get(language)
+  if (cached !== undefined) return cached
+
   try {
-    return new Intl.Locale(language).getTextInfo().direction === 'rtl'
-  } catch (error) {
-    if (error instanceof RangeError) return false
-    throw error
+    const isRightToLeft =
+      new Intl.Locale(language).getTextInfo().direction === 'rtl'
+    languageDirectionCache.set(language, isRightToLeft)
+    return isRightToLeft
+  } catch {
+    languageDirectionCache.set(language, false)
+    return false
   }
 }