Normative: Ensure an Object is returned from calendar.mergeFields()

ptomato · Ms2ger · commit 4e63f25f4adc · 2021-09-09T10:42:18.000+02:00
In each case where CalendarMergeFields is called, it is later asserted in
PrepareTemporalFields that Type(_fields_) is Object. Previously the spec
text failed this assertion.

The tests check that a TypeError is thrown in this case, as well as that
the TypeError is thrown before the value is passed to any dateFromFields()
or similar method.
diff --git a/lib/ecmascript.ts b/lib/ecmascript.ts
@@ -1534,7 +1534,9 @@ export const ES = ObjectAssign({}, ES2020, {
   CalendarMergeFields: (calendar, fields, additionalFields) => {
     const mergeFields = ES.GetMethod(calendar, 'mergeFields');
     if (mergeFields === undefined) return { ...fields, ...additionalFields };
-    return ES.Call(mergeFields, calendar, [fields, additionalFields]);
+    const result = ES.Call(mergeFields, calendar, [fields, additionalFields]);
+    if (ES.Type(result) !== 'Object') throw new TypeError('bad return from calendar.mergeFields()');
+    return result;
   },
   CalendarDateAdd: (calendar, date, duration, options, dateAdd) => {
     if (dateAdd === undefined) {
