Ignore non-string signature fold metadata (#1655)

static/js/emailLibrary/signatureFold.js

@@ -133,7 +133,7 @@ export function _foldSummary(label, iconSvg, meta) {
 // "On <date>, <addr> wrote:". Returns a display string like
 // "Jane Doe · Mon, Apr 18, 2026 at 9:31 AM" or `''`.
 export function _extractQuoteMeta(html) {
-  if (!html) return '';
+  if (typeof html !== 'string' || !html) return '';
   const txt = html
     .replace(/<style[\s\S]*?<\/style>/gi, '')
     .replace(/<[^>]+>/g, ' ')

tests/test_signature_fold_js.py

@@ -0,0 +1,63 @@
+import json
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+
+ROOT = Path(__file__).resolve().parents[1]
+pytestmark = pytest.mark.skipif(not shutil.which("node"), reason="node binary not on PATH")
+
+
+def _node_eval(source: str):
+    result = subprocess.run(
+        ["node", "--input-type=module", "-e", source],
+        cwd=ROOT,
+        check=True,
+        capture_output=True,
+        text=True,
+    )
+    return json.loads(result.stdout)
+
+
+def test_extract_quote_meta_ignores_non_string_inputs():
+    values = _node_eval(
+        """
+        globalThis.document = {
+          createElement() {
+            return {
+              set textContent(value) { this._text = value; },
+              get innerHTML() { return this._text || ''; }
+            };
+          }
+        };
+        const { _extractQuoteMeta } = await import('./static/js/emailLibrary/signatureFold.js');
+        console.log(JSON.stringify({
+          nullValue: _extractQuoteMeta(null),
+          objectValue: _extractQuoteMeta({bad: true})
+        }));
+        """
+    )
+
+    assert values == {"nullValue": "", "objectValue": ""}
+
+
+def test_extract_quote_meta_keeps_outlook_headers():
+    values = _node_eval(
+        """
+        globalThis.document = {
+          createElement() {
+            return {
+              set textContent(value) { this._text = value; },
+              get innerHTML() { return this._text || ''; }
+            };
+          }
+        };
+        const { _extractQuoteMeta } = await import('./static/js/emailLibrary/signatureFold.js');
+        const html = 'From: Alice <alice@example.com> Sent: Monday, May 4, 2026 To: Bob Subject: hi';
+        console.log(JSON.stringify({ meta: _extractQuoteMeta(html) }));
+        """
+    )
+
+    assert values["meta"] == "Alice · Monday, May 4, 2026"