Fix /share and cleanup and reorganize frontend locale loading (#25240)

app/javascript/mastodon/locales/intl_provider.tsx

@@ -0,0 +1,56 @@
+import { useEffect, useState } from 'react';
+
+import { IntlProvider as BaseIntlProvider } from 'react-intl';
+
+import { getLocale, isLocaleLoaded } from './global_locale';
+import { loadLocale } from './load_locale';
+
+function onProviderError(error: unknown) {
+  // Silent the error, like upstream does
+  if (process.env.NODE_ENV === 'production') return;
+
+  // This browser does not advertise Intl support for this locale, we only print a warning
+  // As-per the spec, the browser should select the best matching locale
+  if (
+    error &&
+    typeof error === 'object' &&
+    error instanceof Error &&
+    error.message.match('MISSING_DATA')
+  ) {
+    console.warn(error.message);
+  }
+
+  console.error(error);
+}
+
+export const IntlProvider: React.FC<
+  Omit<React.ComponentProps<typeof BaseIntlProvider>, 'locale' | 'messages'>
+> = ({ children, ...props }) => {
+  const [localeLoaded, setLocaleLoaded] = useState(false);
+
+  useEffect(() => {
+    async function loadLocaleData() {
+      if (!isLocaleLoaded()) {
+        await loadLocale();
+      }
+
+      setLocaleLoaded(true);
+    }
+    void loadLocaleData();
+  }, []);
+
+  if (!localeLoaded) return null;
+
+  const { locale, messages } = getLocale();
+
+  return (
+    <BaseIntlProvider
+      locale={locale}
+      messages={messages}
+      onError={onProviderError}
+      {...props}
+    >
+      {children}
+    </BaseIntlProvider>
+  );
+};