Guard lexical's scrollIntoViewIfNeeded against Safari's bogus RTL caret rect

rollup.config.mjs

@@ -10,6 +10,46 @@ import { promisify } from "util"
 /* global Buffer */
 const brotliPromise = promisify(brotliCompress)
 
+// Interim workaround for facebook/lexical#2495. On Safari, a collapsed caret in
+// RTL text yields a degenerate, out-of-bounds bounding rect, so Lexical's
+// scrollIntoViewIfNeeded scrolls the window up on every space/backspace and the
+// editor jumps off-screen. A caret that lives inside the editor cannot lie
+// entirely above the editor's own top edge; when the rect says it does, the rect
+// is unreliable, so skip the scroll. The guard is one-sided on purpose — a rect
+// below the editor is the normal "scroll the caret into view" path (including
+// auto-scroll inside an overflow:auto editor root) and is left untouched. This
+// injects that guard into the bundled
+// lexical at build time (the Rails-engine build bundles lexical; the npm build
+// externalizes it). Remove once a fixed lexical release is adopted upstream.
+function guardLexicalScrollIntoView() {
+  const PROD_ANCHOR = "if(null===r||null===i)return;let{top:o,bottom:s}=e,l=0,c=0,a=n;"
+  const PROD_GUARD = "if(null===r||null===i)return;const $lxsr=n.getBoundingClientRect();if(e.bottom<$lxsr.top)return;let{top:o,bottom:s}=e,l=0,c=0,a=n;"
+  const DEV_ANCHOR = "  if (doc === null || defaultView === null) {\n    return;\n  }\n  let {\n    top: currentTop,\n    bottom: currentBottom\n  } = selectionRect;"
+  const DEV_GUARD = "  if (doc === null || defaultView === null) {\n    return;\n  }\n  // Injected by Lexxy — skip scroll on a bogus above-the-editor caret rect (Safari RTL). facebook/lexical#2495.\n  const rootRect = rootElement.getBoundingClientRect();\n  if (selectionRect.bottom < rootRect.top) {\n    return;\n  }\n  let {\n    top: currentTop,\n    bottom: currentBottom\n  } = selectionRect;"
+
+  let applied = 0
+  return {
+    name: "guard-lexical-scroll-into-view",
+    buildStart() {
+      applied = 0
+    },
+    transform(code, id) {
+      if (!/[\\/]node_modules[\\/]lexical[\\/]/.test(id)) return null
+      let out = code
+      if (out.includes(PROD_ANCHOR)) out = out.replace(PROD_ANCHOR, PROD_GUARD)
+      if (out.includes(DEV_ANCHOR)) out = out.replace(DEV_ANCHOR, DEV_GUARD)
+      if (out === code) return null
+      applied++
+      return { code: out, map: null }
+    },
+    buildEnd() {
+      if (applied === 0) {
+        this.error("guard-lexical-scroll-into-view: lexical's scrollIntoViewIfNeeded anchor was not found. The workaround for facebook/lexical#2495 did not apply — re-verify it against the current lexical version.")
+      }
+    }
+  }
+}
+
 export default [
   {
     input: "./src/index.js",
@@ -29,6 +69,7 @@ export default [
       "@rails/activestorage"
     ],
     plugins: [
+      guardLexicalScrollIntoView(),
       nodeResolve(),
       commonjs(),
       // Inject Prism for prismjs language components that expect a global Prism