FA-77239 / Calendar recurrence rules / Member archive

Parsing and validating RRULE property text: ordinal range · case 04

BYDAY=0MO is accepted as if it had no ordinal.

Member previewVariant 4 · 3 implementations · 7 checks per implementation

Case contract

Parse "NAME=VALUE;..." rule text. Part names are case-insensitive; empty parts (a trailing ";") are ignored; a part without "=" is malformed; any repeated part name is an error; FREQ is required. INTERVAL defaults to 1 and must be >= 1. BYDAY tokens are an optional signed 1-2 digit ordinal (explicit "+" allowed) followed by MO..SU; a present ordinal must satisfy 1 <= |n| <= 53. Errors are returned as {"error": message}; otherwise {"freq","interval","byday":[[n, day]],"count","until"}.

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
zero ordinal	`{"byday": [[0, "MO"]], "count": null, "freq": "MONTHLY", "interval": 1, "until": null}`	`{"error": "bad ordinal"}`	Failed

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