fix(ext/cron): automatically override unspecified values (#22042)

Fixes #22041

1 files changed, 20 insertions, 1 deletions

diff --git a/ext/cron/01_cron.ts b/ext/cron/01_cron.ts
index 84e5c7fff..c2a0c9cd1 100644
--- a/ext/cron/01_cron.ts
+++ b/ext/cron/01_cron.ts
@@ -62,7 +62,7 @@ export function parseScheduleToString(
   if (typeof schedule === "string") {
     return schedule;
   } else {
-    const {
+    let {
       minute,
       hour,
       dayOfMonth,
@@ -70,6 +70,25 @@ export function parseScheduleToString(
       dayOfWeek,
     } = schedule;
 
+    // Automatically override unspecified values for convenience. For example,
+    // to run every 2 hours, `{ hour: { every: 2 } }` can be specified without
+    // explicitely specifying `minute`.
+    if (minute !== undefined) {
+      // Nothing to override.
+    } else if (hour !== undefined) {
+      // Override minute to 0 since it's not specified.
+      minute = 0;
+    } else if (dayOfMonth !== undefined || dayOfWeek !== undefined) {
+      // Override minute and hour to 0 since they're not specified.
+      minute = 0;
+      hour = 0;
+    } else if (month !== undefined) {
+      // Override minute and hour to 0, and dayOfMonth to 1 since they're not specified.
+      minute = 0;
+      hour = 0;
+      dayOfMonth = 1;
+    }
+
     return formatToCronSchedule(minute) +
       " " + formatToCronSchedule(hour) +
       " " + formatToCronSchedule(dayOfMonth) +