Translations on the server

A moost server with a translator serves workflow forms in the user's language: labels, placeholders, validation messages, finish screens and the built-in UI texts the browser shows. The browser only says which language it wants (Accept-Language, sent by <AsWfForm> from provideAsLocale).

// server: main.ts
import { setTranslator } from "moost";

setTranslator({
  en: {}, // the source language first: the default locale
  de: {
    "First name": "Vorname", // a model text: the text is its own id
    MIN_LENGTH: "Mindestens {min} Zeichen", // a validator message: by code
    UI_CANCEL: "Abbrechen", // a built-in UI text: by code
  },
});

That is all: @atscript/moost-wf registers the message catalogs its forms need when it is imported, and every form step answers in the request's language. setTranslator also takes a function (i18next, FormatJS, …) — see moost's i18n docs for the translator contract and how the request's locale is picked.

What a workflow serves translated

What	Translated by
Form schema texts: @meta.label, @meta.description, constraint messages, @ui.* texts	the text itself
Validation errors of resolveInput() / @WfInput()	the error's code (MIN_LENGTH), params filled
requireInput({ errors, formMessage })	the text you pass
finishWf / abortWf: message.text, button labels, skipButton.label	the text you pass
$i18n on the form schema	— the client's dictionary: message templates and expression texts

The @ui.* texts are placeholder, hint, option labels, submit.text, label.singular, action labels, prefix / suffix, literalLabel labels, nav.group and the array add / remove labels. An option without a value keeps its source label as its value, so submitted values never depend on the language. @ui.form.attr values, class names and styles are not texts.

The workflow's state and context are never translated: they are data. For the languages in the translator's locales (a map's keys, or the locales option), the schema is computed once per form and language — and per translator scope (a tenant, a brand) when the translator has one — and reused for every request; any other locale is translated per request.

$i18n — what the browser translates itself

The form schema carries $i18n, merged by <AsWfForm> into the app's texts:

• the validator's message templates (MIN_LENGTH, …) and the built-in UI texts (UI_*) in the request's language, with {name} placeholders kept;
• the translated string literals of the form's expressions (@ui.form.fn.label, @ui.form.fn.value, @ui.form.validate, …): a result that is exactly one of them is shown translated, and t(text, params) in an expression reads them — the way to translate the text of a display-only ui.paragraph. See Texts in the user's language.

Only entries that differ from English are sent.

Registered templates are public

Every template registered with moost's registerMessages is sent, translated, in the $i18n of every form schema (and of /meta responses of @atscript/moost-db). Register only texts a user may see — never secrets or internal messages.

Tables without workflows

@atscript/moost-db (since 0.1.170) serves /meta and action forms in the request's language with their own $i18n, which tables, value help and action forms merge into the app's texts (Tables, value help and action forms). @atscript/moost-wf registers AS_UI_MESSAGES on import. An app that serves tables but no workflow forms registers the built-in UI texts once itself, so /meta carries them translated:

import { registerMessages } from "moost";
import { AS_UI_MESSAGES } from "@atscript/ui/messages";

registerMessages(AS_UI_MESSAGES);

Opting out

serializeFormSchema(Form, { translate: false }), useAtscriptWf(Form, { translate: false }) and @WfInput({ translate: false }) serve a form's source texts — for wording that depends on more than the language (per tenant, per role), which the per-language schema cache cannot hold. Error messages and finish texts are still translated per request.

DOs and DON'Ts

• Do write texts as whole literals in expressions (t("Hello {name}", { name })), never "Hello " + name.
• Do branch on error codes, never on messages. The abort reason is a machine value and is never translated: put the user-facing text in message.
• Don't translate texts yourself before passing them to finishWf or requireInput: pass the source text, the server translates it.
• Do recompile your .as forms with this @atscript/ui version before you turn a translator on: forms compiled by an older plugin carry options without explicit values, whose value would then follow the translated label.
• Labels derived from field names (no @meta.label) are not translated — give translatable fields a @meta.label.

See also

• Language & Translations: the client side, provideAsLocale.
• @atscript/moost-wf reference: serializeFormSchema, useAtscriptWf, finishWf.
• Finish Screens.