FA-77029 / Calendar recurrence rules / Member archive

Splitting a series for a this-and-following edit: degenerate split · case 04

Editing from the first occurrence leaves an empty head series behind.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

A daily-interval series (dtstart, interval, and either count or until). Editing from 0-based occurrence k splits it: the head keeps occurrences 0..k-1 (count k, or until = its last retained occurrence date) and the tail starts at the original date of occurrence k with new_interval and the remaining count (or the original until). k <= 0 makes the head None; a split at or past the end makes the tail None. Return {"head": [dtstart, count, until] or None, "tail": [start, interval, count, until] or None}.

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
until split at first	`{"head": ["2024-03-01", null, "2024-02-23"], "tail": ["2024-03-01", 14, null, "2024-06-01"]}`	`{"head": null, "tail": ["2024-03-01", 14, null, "2024-06-01"]}`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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