todo.reschedule-recurrence

def reschedule_recurrence(recurrence: Optional[Recurrence], from_due: Optional[str], to_due: Optional[str]) -> Optional[Recurrence]

from fune.todo.reschedule_recurrence import reschedule_recurrence  # todo.reschedule-recurrence@^1

from dataclasses import replace
from typing import Optional

from .dates_add_days import add_days  ← from dates.add-days ^1.0.0 · built alongside by fune
from .todo_item import Recurrence  ← from todo.item ^1.0.0 · built alongside by fune


def reschedule_recurrence(
    recurrence: Optional[Recurrence], from_due: Optional[str], to_due: Optional[str]
) -> Optional[Recurrence]:
    """The repeat a todo keeps when its due date is edited: a moved date becomes the anchor."""
    # add_days(x, 0) is the date check: it raises dates.add-days's message.
    if from_due is not None:
        add_days(from_due, 0)
    if to_due is not None:
        add_days(to_due, 0)
    if recurrence is None:
        return None
    add_days(recurrence.anchor, 0)
    # No date: todo.item's validate_draft says a repeating todo needs one.
    if to_due is None or to_due == from_due:
        return recurrence
    return replace(recurrence, anchor=to_due)

Install

fune build

With that line in your source, in a Python project (language python in fune.project), fune build resolves it and its 2 dependencies, pins them in fune.lock, downloads only the Python 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. 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 Python implementation. Install it without the registry with fune add ./todo.reschedule-recurrence-1.0.0-python.fune, or fetch it from a terminal with fune pull todo.reschedule-recurrence@1.0.0:python.

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