fix(ui): conditionally load core-js polyfills for old Android WebViews

The es2019 down-level fixed the parse error, but the Chromium 66 in-app WebView (Android 9) then threw "Uncaught ReferenceError: globalThis is not defined" — esbuild lowers syntax, not the es2020+ runtime globals the bundle and its deps reference (globalThis, structuredClone, Array.at, Object.hasOwn, Promise.allSettled, …), so the module still failed to evaluate and the SPA stayed a white screen. Load core-js only where it is actually missing. A permanent ES5 gate in index.html feature-detects the engine and, on an old one, document.writes a parser-blocking <script src=polyfills.js> before the deferred module runs; a modern engine matches none of the checks and downloads nothing. document.write is used deliberately — it is the only way to inject a script guaranteed to run before a deferred module — with a static literal argument (no interpolation, no injection surface). vite.config emitPolyfills writes dist/polyfills.js from the prebuilt core-js-bundle and keeps it out of the module graph, so the bundle-size budget is unaffected (app entry still 108.8 / 110 KB gzip). pnpm-workspace denies core-js-bundle's install script (the package ships a prebuilt minified.js we only read at build time; its script is a funding banner). svelte-check and the mock e2e (Chromium + WebKit) are green and the size gate still passes. The on-device re-test on the Chromium 66 emulator is pending.
2026-07-04 17:03:49 +02:00
parent 6dfd5203d7
commit 4a0c296bbb
5 changed files with 67 additions and 7 deletions
@@ -2,6 +2,32 @@
 <html lang="ru">
  <head>
    <meta charset="UTF-8" />
+    <!-- Old-engine polyfills. An old Android System WebView (seen: Chromium 66 in the Telegram/VK
+         in-app browser) supports ES modules but lacks the es2020+ runtime globals the bundle and its
+         deps call (globalThis, structuredClone, Array.at, …); they throw a ReferenceError, the module
+         never mounts and the SPA is a white screen. Feature-detect that and synchronously pull core-js
+         (emitted as polyfills.js) BEFORE the deferred module runs. A modern engine matches none of
+         these checks and loads nothing — zero extra bytes, and polyfills.js stays out of the module
+         graph the bundle-size budget measures. document.write is deliberate here: it is the only way
+         to inject a parser-blocking <script> guaranteed to execute before the deferred module (a
+         dynamically-appended script is async and could run after it). The written string is a static
+         literal — no interpolation, so no injection surface. -->
+    <script>
+      (function () {
+        var need =
+          typeof globalThis === 'undefined' ||
+          typeof structuredClone === 'undefined' ||
+          typeof WeakRef === 'undefined' ||
+          typeof queueMicrotask === 'undefined' ||
+          !Array.prototype.at ||
+          !Array.prototype.findLast ||
+          !Object.hasOwn ||
+          !Object.fromEntries ||
+          !Promise.allSettled ||
+          !Promise.any;
+        if (need) document.write('<script src="polyfills.js"><\/script>');
+      })();
+    </script>
    <!-- The SPA shell is an empty client-rendered document behind the public landing — keep it
         out of search indexes (robots.txt deliberately does NOT disallow /app/, so crawlers can
         reach this tag). -->