Ignore non-string calendar date inputs (#1649)

static/js/calendar/utils.js

@@ -118,13 +118,17 @@ export function _ds(d) {
 }
 
 export function _addDays(dateStr, n) {
+  if (typeof dateStr !== 'string' || !dateStr) return '';
   const d = new Date(dateStr + 'T00:00:00');
+  if (isNaN(d)) return '';
   d.setDate(d.getDate() + n);
   return _ds(d);
 }
 
 export function _shiftDT(iso, days) {
+  if (typeof iso !== 'string' || !iso) return '';
   const d = new Date(iso);
+  if (isNaN(d)) return '';
   d.setDate(d.getDate() + days);
   return _ds(d) + (iso.length > 10 ? 'T' + iso.slice(11) : '');
 }
@@ -147,7 +151,7 @@ export function _tzOffset() {
 // bucket by the USER's local date. Without this an event at
 // "2026-05-13T22:00:00Z" (07:00 May 14 JST) would render on May 13.
 export function _localDateOf(isoStr) {
-  if (!isoStr) return '';
+  if (typeof isoStr !== 'string' || !isoStr) return '';
   if (isoStr.length === 10) return isoStr;
   if (/[Zz]$|[+\-]\d{2}:?\d{2}$/.test(isoStr)) {
     const d = new Date(isoStr);

tests/test_calendar_utils_dates_js.py

@@ -0,0 +1,64 @@
+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_calendar_date_helpers_ignore_non_string_inputs():
+    values = _node_eval(
+        """
+        import { _addDays, _shiftDT, _localDateOf } from './static/js/calendar/utils.js';
+        console.log(JSON.stringify({
+          addNull: _addDays(null, 1),
+          addObject: _addDays({bad: true}, 1),
+          shiftNull: _shiftDT(null, 1),
+          shiftObject: _shiftDT({bad: true}, 1),
+          localNull: _localDateOf(null),
+          localNumber: _localDateOf(123)
+        }));
+        """
+    )
+
+    assert values == {
+        "addNull": "",
+        "addObject": "",
+        "shiftNull": "",
+        "shiftObject": "",
+        "localNull": "",
+        "localNumber": "",
+    }
+
+
+def test_calendar_date_helpers_keep_valid_strings():
+    values = _node_eval(
+        """
+        import { _addDays, _shiftDT, _localDateOf } from './static/js/calendar/utils.js';
+        console.log(JSON.stringify({
+          add: _addDays('2026-06-01', 2),
+          shift: _shiftDT('2026-06-01T10:30:00', 1),
+          local: _localDateOf('2026-06-01T23:30:00Z')
+        }));
+        """
+    )
+
+    assert values["add"] == "2026-06-03"
+    assert values["shift"] == "2026-06-02T10:30:00"
+    assert isinstance(values["local"], str)
+    assert len(values["local"]) == 10