type.batch_row_invalid

A file helper's rows can't be read as the type its as: names or from where its items_at: says, its max_unpacked_size: isn't a size, or its rows can't be written as the row its each: gives.

Area 12, Background work; not declinable; the next step is usually the agent's.

A file helper reads each row as the Input its as: names, and writes each as the Output its each: gives. A CSV or TSV row holds one value a cell, so a row type holding a list, a map, an object or a standard type with no one text form is refused, pointing at JSON Lines, whose rows hold any JSON value; so is a row type that isn't an Input (or, written, an Output), or two fields reading or writing one column. The same rule refuses json.read's items_at: when it isn't member names written out between dots ("data.items"), and a reader's max_unpacked_size: when it isn't a size (200mb):

use bakery/types { OrderCode }/// One order a sheet lists, with its lines.type OrderRow = Input {    reference: OrderCode    lines: List<OrderCode>}

use bakery/entities { OrderSheet, OrderSheetNotFound }use bakery/types { OrderRow }use bakery/actions { take_order }/// Starts taking the orders a kept sheet lists.action read_orders(sheet_id: OrderSheet.id) fails OrderSheetNotFound -> BatchRun {    var order_sheet: OrderSheet = attempt OrderSheet.get(sheet_id)    return csv.read(order_sheet.sheet, as: OrderRow, each: order_entry -> take_order(order_entry))}

  |8 |     return csv.read(order_sheet.sheet, as: OrderRow, each: order_entry -> take_order(order_entry))  |                                            ^^^^^^^^ `OrderRow.lines` holds a list