fix(mobile): prevent invalid HTML entities from crashing markdown (#6495)

Co-authored-by: Simone <185146821+Lucenx9@users.noreply.github.com>

Author: Lucenx9

apps/mobile/modules/t3-markdown-text/src/nativeMarkdownText.ts

@@ -70,15 +70,22 @@ const EMPTY_CONTEXT: RunContext = {
 
 const INLINE_HTML_TAG_PATTERN = /<\/?(?:kbd|mark|sub|sup|u)(?:\s[^>]*)?>/gi;
 
+function decodeCodePoint(codePoint: number, entity: string): string {
+  if (!Number.isInteger(codePoint) || codePoint < 0 || codePoint > 0x10ffff) {
+    return entity;
+  }
+  return String.fromCodePoint(codePoint);
+}
+
 function decodeHtmlEntitiesOnce(value: string): string {
   return value.replace(
     /&(?:#(\d+)|#x([0-9a-f]+)|amp|apos|gt|lt|nbsp|quot);/gi,
     (entity, decimal: string | undefined, hexadecimal: string | undefined) => {
       if (decimal) {
-        return String.fromCodePoint(Number.parseInt(decimal, 10));
+        return decodeCodePoint(Number.parseInt(decimal, 10), entity);
       }
       if (hexadecimal) {
-        return String.fromCodePoint(Number.parseInt(hexadecimal, 16));
+        return decodeCodePoint(Number.parseInt(hexadecimal, 16), entity);
       }
       switch (entity.toLowerCase()) {
         case "&amp;":

apps/mobile/src/lib/nativeMarkdownText.test.ts

@@ -126,6 +126,22 @@ describe("nativeMarkdownTextRuns", () => {
     ]);
   });
 
+  it.each([
+    ["😀", "😀"],
+    ["🚀", "🚀"],
+    ["�", "�"],
+    ["�", "�"],
+    ["�", "�"],
+    ["�", "�"],
+  ])("normalizes numeric entity %s without throwing", (content, expected) => {
+    const node: MarkdownNode = {
+      type: "paragraph",
+      children: [{ type: "text", content }],
+    };
+
+    expect(nativeMarkdownTextRuns(node)).toEqual([{ text: expected }]);
+  });
+
   it("reads inline content from nested text nodes", () => {
     const node: MarkdownNode = {
       type: "paragraph",