Define well-known RTL locales before calling `getLocaleInfo()` for default locale (#2167)

2 files changed, 8 insertions, 3 deletions

diff --git a/.changeset/odd-sheep-love.md b/.changeset/odd-sheep-love.md
new file mode 100644
index 00000000..04a53315
--- /dev/null
+++ b/.changeset/odd-sheep-love.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/starlight': patch
+---
+
+Fixes an issue detecting the built-in locale when running Starlight in a web container environment on Firefox
diff --git a/packages/starlight/utils/i18n.ts b/packages/starlight/utils/i18n.ts
index ce07b1cc..5ec66722 100644
--- a/packages/starlight/utils/i18n.ts
+++ b/packages/starlight/utils/i18n.ts
@@ -2,9 +2,6 @@ import type { AstroConfig } from 'astro';
 import { AstroError } from 'astro/errors';
 import type { StarlightConfig } from './user-config';
 
-/** Informations about the built-in default locale used as a fallback when no locales are defined. */
-export const BuiltInDefaultLocale = { ...getLocaleInfo('en'), lang: 'en' };
-
 /**
  * A list of well-known right-to-left languages used as a fallback when determining the text
  * direction of a locale is not supported by the `Intl.Locale` API in the current environment.
@@ -14,6 +11,9 @@ export const BuiltInDefaultLocale = { ...getLocaleInfo('en'), lang: 'en' };
  */
 const wellKnownRTL = ['ar', 'fa', 'he', 'prs', 'ps', 'syc', 'ug', 'ur'];
 
+/** Informations about the built-in default locale used as a fallback when no locales are defined. */
+export const BuiltInDefaultLocale = { ...getLocaleInfo('en'), lang: 'en' };
+
 /**
  * Processes the Astro and Starlight i18n configurations to generate/update them accordingly:
  *