todo.reschedule-recurrence

pub fn reschedule_recurrence(recurrence: Option<&Recurrence>, from_due: Option<&str>, to_due: Option<&str>) -> Option<Recurrence>

fune!(todo.reschedule-recurrence@^1);  // then call reschedule_recurrence(…)

use super::funejson::Value;  ← the fune runtime: the JSON value the test vectors use; fune build keeps it only where a signature takes one
use super::dates_add_days::add_days;  ← from dates.add-days ^1.0.0 · built alongside by fune
use super::todo_item::Recurrence;  ← from todo.item ^1.0.0 · built alongside by fune
use super::todo_item_validate_draft::{recurrence_from_value, recurrence_to_value};

/// The repeat a todo keeps when its due date is edited: a moved date becomes
/// the anchor; an unchanged date keeps it (so a month-end series that has
/// rolled forward stays on the month end).
///
/// # Panics
/// On a malformed or impossible date (dates.add-days's message).
pub fn reschedule_recurrence(recurrence: Option<&Recurrence>, from_due: Option<&str>, to_due: Option<&str>) -> Option<Recurrence> {
    if let Some(date) = from_due {
        add_days(date, 0);
    }
    if let Some(date) = to_due {
        add_days(date, 0);
    }
    let rule = recurrence?;
    add_days(&rule.anchor, 0);
    match to_due {
        Some(date) if Some(date) != from_due => Some(Recurrence { anchor: date.to_string(), ..rule.clone() }),
        _ => Some(rule.clone()),
    }
}

fn opt_date(v: &Value) -> Option<&str> {
    if v.is_null() { None } else { Some(v.as_str()) }
}

pub fn fune_vector(args: &[Value]) -> Value {
    let rule = recurrence_from_value(&args[0]);
    recurrence_to_value(&reschedule_recurrence(rule.as_ref(), opt_date(&args[1]), opt_date(&args[2])))
}

Install

fune build

With that line in your source, in a Rust project (language rust in fune.project), fune build resolves it and its 2 dependencies, pins them in fune.lock, downloads only the Rust package of each, and builds the code above into your project’s .fune/build, one readable file per capability with a header linking back here. A crate’s build.rs runs it before every compile. Or pin a range in fune.project and build in one step:

fune add todo.reschedule-recurrence

The manifest, vectors and README with only the Rust implementation. Install it without the registry with fune add ./todo.reschedule-recurrence-1.0.0-rust.fune, or fetch it from a terminal with fune pull todo.reschedule-recurrence@1.0.0:rust.

The whole function, every language, is one file too: todo.reschedule-recurrence-1.0.0.fune, 9,618 bytes, sha256 32bbf5607d31a2d70a36741adcf309620dd29de47922d0b5e4045c5976eb5451. It installs into a project of any language.

// fune: before todo.reschedule-recurrence

// fune: after todo.reschedule-recurrence

// fune: replace dates.add-days in todo.reschedule-recurrence
// fune: replace todo.item in todo.reschedule-recurrence

// fune: step todo.reschedule-recurrence after <n|label>

More from the author

| recurrence | fromDue → toDue | result | | --- | --- | --- | | null | anything | null | | any | toDue null | unchanged (validateDraft then says a repeating todo needs a due date) | | any | toDue = fromDue | unchanged | | any | toDue ≠ fromDue | the same frequency and interval, anchored on toDue |

- **An unchanged date keeps the anchor.** A monthly series from 31 January is due 28 February after one roll forward; saving an edit to its title must not re-anchor it on the 28th, or it would lose the month end. - A new date is taken as given, even a Saturday for a weekday series: todo.next-occurrence decides the following dates from there. - Every date given (`fromDue`, `toDue`, the anchor) must be a real ISO date, with or without a recurrence; the messages are dates.add-days's (`"2026-02-30" is not a real calendar date`).

Files