Matrix: suppress auto-linked file refs

extensions/matrix/src/matrix/format.test.ts

@@ -14,6 +14,19 @@ describe("markdownToMatrixHtml", () => {
     expect(html).toContain('<a href="https://example.com">docs</a>');
   });
 
+  it("does not auto-link bare file references into external urls", () => {
+    const html = markdownToMatrixHtml("Check README.md and backup.sh");
+    expect(html).toContain("README.md");
+    expect(html).toContain("backup.sh");
+    expect(html).not.toContain('href="http://README.md"');
+    expect(html).not.toContain('href="http://backup.sh"');
+  });
+
+  it("keeps real domains linked even when path segments look like filenames", () => {
+    const html = markdownToMatrixHtml("See https://docs.example.com/backup.sh");
+    expect(html).toContain('href="https://docs.example.com/backup.sh"');
+  });
+
   it("escapes raw HTML", () => {
     const html = markdownToMatrixHtml("<b>nope</b>");
     expect(html).toContain("&lt;b&gt;nope&lt;/b&gt;");

extensions/matrix/src/matrix/format.ts

@@ -11,10 +11,63 @@ md.enable("strikethrough");
 
 const { escapeHtml } = md.utils;
 
+/**
+ * Keep bare file references like README.md from becoming external http:// links.
+ * Telegram already hardens this path; Matrix should not turn common code/docs
+ * filenames into clickable registrar-style URLs either.
+ */
+const FILE_EXTENSIONS_WITH_TLD = new Set(["md", "go", "py", "pl", "sh", "am", "at", "be", "cc"]);
+
+function isAutoLinkedFileRef(href: string, label: string): boolean {
+  const stripped = href.replace(/^https?:\/\//i, "");
+  if (stripped !== label) {
+    return false;
+  }
+  const dotIndex = label.lastIndexOf(".");
+  if (dotIndex < 1) {
+    return false;
+  }
+  const ext = label.slice(dotIndex + 1).toLowerCase();
+  if (!FILE_EXTENSIONS_WITH_TLD.has(ext)) {
+    return false;
+  }
+  const segments = label.split("/");
+  if (segments.length > 1) {
+    for (let i = 0; i < segments.length - 1; i += 1) {
+      if (segments[i]?.includes(".")) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+function shouldSuppressAutoLink(
+  tokens: Parameters<NonNullable<typeof md.renderer.rules.link_open>>[0],
+  idx: number,
+): boolean {
+  const token = tokens[idx];
+  if (token?.type !== "link_open" || token.info !== "auto") {
+    return false;
+  }
+  const href = token.attrGet("href") ?? "";
+  const label = tokens[idx + 1]?.type === "text" ? (tokens[idx + 1]?.content ?? "") : "";
+  return Boolean(href && label && isAutoLinkedFileRef(href, label));
+}
+
 md.renderer.rules.image = (tokens, idx) => escapeHtml(tokens[idx]?.content ?? "");
 
 md.renderer.rules.html_block = (tokens, idx) => escapeHtml(tokens[idx]?.content ?? "");
 md.renderer.rules.html_inline = (tokens, idx) => escapeHtml(tokens[idx]?.content ?? "");
+md.renderer.rules.link_open = (tokens, idx, _options, _env, self) =>
+  shouldSuppressAutoLink(tokens, idx) ? "" : self.renderToken(tokens, idx, _options);
+md.renderer.rules.link_close = (tokens, idx, _options, _env, self) => {
+  const openIdx = idx - 2;
+  if (openIdx >= 0 && shouldSuppressAutoLink(tokens, openIdx)) {
+    return "";
+  }
+  return self.renderToken(tokens, idx, _options);
+};
 
 export function markdownToMatrixHtml(markdown: string): string {
   const rendered = md.render(markdown ?? "");