FA-77080 / Calendar recurrence rules / Member archive

Occurrence test and next-occurrence lookup for an anchored N-weekly series: next index · case 05

Querying on an occurrence date returns that same date as the next occurrence.

Member previewVariant 5 · 3 implementations · 8 checks per implementation

Case contract

A series occurs every interval_weeks weeks starting at anchor, for count occurrences. For a query date return [is_occurrence, next occurrence strictly after the query or None, 0-based index of that next occurrence or None]. Dates before the anchor are never occurrences; the next occurrence after a query before the anchor is the anchor itself.

Why this case matters

Recurring calendar series are expanded into concrete instances for display, reminders and conflict checks.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
four-weekly aligned	`[true, "2024-04-29", 2]`	`[true, "2024-05-27", 3]`	Failed

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