type.batch_from_invalid: A batch's from: is something other than a call of a named query that gives a Page, such as a query that gives a List

A batch's from: is something other than a call of a named query that gives a Page, such as a query that gives a List.

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

Why Jadpo refuses it

A batch, such as batches.each or a file's write helper, walks from: a page at a time in the background, after the action that starts it commits. The run keeps the cursor of the next page, so a crash or a deploy carries on where it stopped. A query that gives a List, or a page already read, has no cursor to keep, so the run couldn't keep its place.

What it looks like

main.jadpo, beside a stock.jadpo that declares Item, a paged query items and the action mark_seen:

example

query first_items() -> List<Item> {    from: Item    order: [Item.code asc]    limit: 10}action sweep_shelf() -> BatchRun {    return batches.each(from: first_items(), each: item -> mark_seen(item))}

jadpo checkcheck failed: 1 error, 2 files

error batches.each's from: isn't a call of a named query giving a Page

--> main.jadpo:8:31

  |8 |     return batches.each(from: first_items(), each: item -> mark_seen(item))  |                               ^^^^^^^^^^^^^ gives `List<Item>`

reason: A run walks from: a page at a time, after the action that starts it commits: it calls a named query that gives a Page<T>, and each item is a T; the query's arguments are worked out now and saved with the run.
next: Write batches.each(from: <query>(...), ...), with a query whose result is Page<T> (agent)
rule: type.batch_from_invalid
help: https://jadpo.dev/docs/errors/type.batch_from_invalid

(agent) at the end of the next: line means your coding agent can make the fix itself.

How to fix it

If a query giving a Page of the items already exists, give the action that query's page settings and call it in from:. In main.jadpo, which no longer needs first_items:

example

action sweep_shelf(page: ItemPage) -> BatchRun {    return batches.each(from: items(page), each: item -> mark_seen(item))}

The run now reads Items in pages of the size page.page_size gives, 25 by default, and calls mark_seen for each. It orders them by id, which no update changes, so each item is seen exactly once.

When there is only a list's query, make it give a Page instead: an order: it can page through and a page: with its size and cursor, in place of limit:. That is the shape of items in stock.jadpo.

Why Jadpo refuses it

What it looks like

How to fix it

Related