todo.export-csv

def export_csv(todos: Sequence[Todo]) -> str

from fune.todo.export_csv import export_csv  # todo.export-csv@^1

from typing import List, Sequence

from .todo_item import Todo  ← from todo.item ^1.0.0 · built alongside by fune

_HEADER = (
    "id", "title", "notes", "done", "priority", "due", "tags",
    "recurrenceFrequency", "recurrenceInterval", "recurrenceAnchor", "createdAt", "completedAt", "order",
)


def _field(text: str) -> str:
    """Quote a field only when RFC 4180 needs it: a comma, a double quote, CR or LF."""
    if not any(ch in text for ch in ',"\r\n'):
        return text
    return '"' + text.replace('"', '""') + '"'


def export_csv(todos: Sequence[Todo]) -> str:
    """Todos as CSV under a fixed 13-column header, one CRLF-ended row each, in the order given."""
    lines: List[str] = [",".join(_HEADER)]
    for todo in todos:
        rule = todo.recurrence
        cells = [
            todo.id,
            todo.title,
            todo.notes if todo.notes is not None else "",
            "true" if todo.done else "false",
            todo.priority,
            todo.due if todo.due is not None else "",
            " ".join(todo.tags),
            "" if rule is None else rule.frequency,
            "" if rule is None else str(rule.interval),
            "" if rule is None else rule.anchor,
            todo.created_at,
            todo.completed_at if todo.completed_at is not None else "",
            str(todo.order),
        ]
        lines.append(",".join(_field(cell) for cell in cells))
    return "".join(line + "\r\n" for line in lines)

Install

fune build

With that line in your source, in a Python project (language python in fune.project), fune build resolves it and its 1 dependency, 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.export-csv

The manifest, vectors and README with only the Python implementation. Install it without the registry with fune add ./todo.export-csv-1.0.0-python.fune, or fetch it from a terminal with fune pull todo.export-csv@1.0.0:python.

The whole function, every language, is one file too: todo.export-csv-1.0.0.fune, 17,768 bytes, sha256 f2f17720f311707190e8643af25b46732546ab8cf545f39a5f5f873f7139bc83. It installs into a project of any language.

# fune: before todo.export-csv

# fune: after todo.export-csv

# fune: replace todo.item in todo.export-csv

# fune: step todo.export-csv after <n|label>

More from the author

CSV as in [RFC 4180, Common Format and MIME Type for Comma-Separated Values (CSV) Files](https://www.rfc-editor.org/rfc/rfc4180). The same format is written by todo.export-csv and read by todo.import-csv.

- A header row, then one row per todo. todo.export-csv writes these 13 columns in this order: `id,title,notes,done,priority,due,tags,recurrenceFrequency,recurrenceInterval,recurrenceAnchor,createdAt,completedAt,order` - `done` is `true` or `false`. `tags` are joined with single spaces. The repeat takes three columns, all empty when the todo does not repeat. `order` and `recurrenceInterval` are decimal integers. A null field (`notes`, `due`, `completedAt`) is empty. - A field is quoted with double quotes exactly when it contains a comma, a double quote, CR or LF, and a double quote inside it is doubled. Nothing else is quoted, and spaces are kept as they are. - Every row, the last one included, ends with CRLF.

**Caveat for spreadsheets.** Nothing is escaped against formula injection: a title such as `=1+1` or `=HYPERLINK(...)` is written as it is, because prefixing it with `'` would change the title when the file is read back. If your app offers the file for opening in Excel, LibreOffice or Google Sheets, warn people, or write a separate spreadsheet export that escapes cells starting with `=`, `+`, `-` or `@`.

## Why it is shaped this way

One column per field, with the repeat split into three plain columns rather than packed into one, so the file is readable in a spreadsheet and easy for other tools to produce. Columns are named after the `Todo` fields, so the header documents itself.

CRLF line endings and minimal quoting are what RFC 4180 describes and what spreadsheets expect; quoting only when needed keeps the file diff-friendly.

## Edge cases

- No todos: just the header line, still ending in CRLF. - Notes that are `""` are written as an empty field, the same as null notes, so they read back as null. Every other valid list reads back exactly: `importCsv(exportCsv(todos))` equals `todos`. - Line breaks inside notes (LF, CRLF or a lone CR) are kept inside quotes as they are. - It does not validate and never throws: a todo is written as it is, even an invalid one (a negative order is written `-1`). Validate on the way in, or let todo.import-csv refuse the file. - The text is a string; encode it as UTF-8 when saving. No byte order mark is written (some versions of Excel need one to read UTF-8; add `\uFEFF` in front if yours does, todo.import-csv accepts it).

Files