Use django's gettext in Svelte

Wrapper around django's JavaScript i18n features in Svelte.

Django docs: Using the JavaScript translation catalog

In your rollup configuration:

import svelte from 'rollup-plugin-svelte';
import { writeGettextExtracts, gettextStringExtractor } from 'svelte-django-gettext/build';

export default {
    input: 'app.js',
    output: {...},
    plugins: [
        svelte({
            preprocessors: {
                markup: gettextStringExtractor
            }
        }),
        writeGettextExtracts('js/_svelte_django_extracted_messages.js'),
    ]
}

Or with vite:

import { defineConfig } from 'vite';
import { svelte } from '@sveltejs/vite-plugin-svelte';

import { gettextStringExtractor, writeGettextExtracts } from 'svelte-django-gettext/build';

export default defineConfig({
    base: '',
    plugins: [
        svelte({
            preprocess: {
                markup: gettextStringExtractor
            },
        }),
        writeGettextExtracts('js/_svelte_django_extracted_messages.js'),
    ],
});

In your application:

<script>
import gettext from 'svelte-django-gettext';

</script>

<h1>{gettext('hello')}</h1>

Make sure the page loads the generated catalog, from a django template: <script src="{% url 'javascript-catalog' %}"></script>. If this is not the case, all functions will just return their message id.

How it works:

Django's ./manage.py makemessages cannot parse .svelte files to extract gettext() calls. A preprocessor extracts gettext() calls and outputs _svelte_django_extracted_messages.js, which then contains gettext calls extracted from your .svelte files.

This file should be added to .gitignore, but Django's makemessages management command can read translations strings from it.