I18N: Add translation support for script modules

[manzoorwanijk]

Summary

Adds translation support for script modules (WP_Script_Modules), mirroring the existing wp_set_script_translations() infrastructure for classic scripts.

Script modules (ES modules registered via wp_register_script_module()) currently have no way to load i18n translation data. This means any strings using __() from @wordpress/i18n inside script modules remain untranslated. This affects the new admin pages in WordPress 7.0+ that are built as script modules, including Connectors and Fonts.

Trac ticket: https://core.trac.wordpress.org/ticket/65015

Changes

New public API

• wp_set_script_module_translations( $id, $domain, $path ) — registers a text domain for a script module (in script-modules.php)
• load_script_module_textdomain( $id, $domain, $path ) — loads translation JSON files for a script module, resolving the file path from the module's source URL (in l10n.php)

WP_Script_Modules class changes

• Added set_translations() method — stores text domain and translation path per module
• Added get_registered_src() method — public accessor for a module's raw source URL (used by load_script_module_textdomain())
• Added print_script_module_translations() method — outputs inline <script> tags calling wp.i18n.setLocaleData() for each enqueued module with translations
• Hooked print_script_module_translations() at priority 11 on admin_print_footer_scripts (after classic scripts load wp-i18n at priority 10) and priority 21 on wp_footer (after wp_print_footer_scripts at priority 20)

Automatic translation setup

• wp_default_script_modules() now calls wp_set_script_module_translations() for all @wordpress/* script modules that list wp-i18n in their dependencies

Tests

• 7 new unit tests covering set_translations(), get_registered_src(), wp_set_script_module_translations(), and print_script_module_translations()

How it works

The flow mirrors classic script translations:

1. wp_set_script_module_translations() is called after registering a script module, storing the text domain and optional path
2. When the page renders, print_script_module_translations() iterates over all enqueued modules (and their dependencies) that have translations set
3. For each, it calls load_script_module_textdomain() which resolves the module's source URL to a relative path, computes an MD5 hash, and looks for the corresponding JSON translation file (same naming convention as classic scripts)
4. If found, it outputs an inline <script> calling wp.i18n.setLocaleData() with the translated strings
5. These inline scripts execute before the deferred ES modules, ensuring translations are available when modules run

Related

• Gutenberg PR: I18N: Add translation support for script modules gutenberg#77214 — updates build templates to call wp_set_script_module_translations() for route and package script modules, and adds a polyfill for WP < 7.1.

Test plan

Automated tests

Run the script module tests, which now include end-to-end coverage for translation printing:

npm run test:php -- --group script-modules

The new tests test_print_script_module_translations_outputs_set_locale_data and test_print_script_module_translations_includes_dependencies use the pre_load_script_translations filter to provide mock translations (no fixture files needed) and assert that the rendered inline script contains the expected wp.i18n.setLocaleData() call with the translated data.

Manual verification (optional)

Language packs don't include JSON translation files for the new script modules yet, so manual end-to-end verification requires a small mu-plugin to provide mock translations. Paired with the companion Gutenberg PR (#77214), no wp_set_script_module_translations() registration is needed — the build templates call it automatically.

1. Set up the test environment:

• Switch the site language to any non-English language in Settings > General
• Drop the following mu-plugin into src/wp-content/mu-plugins/test-script-module-translations.php (create the mu-plugins directory if it doesn't exist):

test-script-module-translations.php

<?php
/**
 * Test mu-plugin: Provides mock translations for the connectors content module.
 * DELETE after testing.
 *
 * Registers translations for the connectors route module (since `routes.php` in
 * `src/wp-includes/build/` is auto-generated and doesn't yet call
 * `wp_set_script_module_translations()` — that change lives in Gutenberg PR #77214),
 * and provides mock Spanish translations via the `pre_load_script_translations`
 * filter so no language pack JSON files are needed.
 */

add_action( 'admin_enqueue_scripts', function () {
	add_action( 'options-connectors-wp-admin_init', function () {
		wp_set_script_module_translations( 'wp/routes/connectors-home/content', 'default' );
	}, 20 );
}, 5 );

add_filter( 'pre_load_script_translations', function ( $translations, $file, $handle ) {
	if ( 'wp/routes/connectors-home/content' !== $handle ) {
		return $translations;
	}
	return wp_json_encode( array(
		'locale_data' => array(
			'messages' => array(
				''           => array( 'domain' => 'messages', 'lang' => 'es' ),
				'Set up'     => array( 'Configurar' ),
				'Install'    => array( 'Instalar' ),
				'Connectors' => array( 'Conectores' ),
			),
		),
	) );
}, 10, 3 );

2. Verify:

• Navigate to Settings > Connectors (/wp-admin/options-connectors.php)
• Expected: The heading shows "Conectores" and buttons show "Instalar" / "Configurar"
• View page source and search for js-module-translations — inline <script> tags with IDs like wp/routes/connectors-home/content-js-module-translations should appear after the classic scripts

3. Clean up:

• Delete src/wp-content/mu-plugins/test-script-module-translations.php

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 4.6
Used for: Implementation, tests, and PR description were authored with AI assistance; reviewed and tested by me.

[github-actions]

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[github-actions]

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[github-actions]

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[mukeshpanchal27]

Thanks for the PR! Can you expose which AI tool do you use in PR?

## Use of AI Tools

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You are free to use artificial intelligence (AI) tooling to contribute, but you must disclose what tooling you are using and to what extent a pull request has been authored by AI. It is your responsibility to review and take responsibility for what AI generates. See the WordPress AI Guidelines: <https://make.wordpress.org/ai/handbook/ai-guidelines/>.

Example disclosure:

AI assistance: Yes
Tool(s): GitHub Copilot, ChatGPT
Model(s): GPT-5.1
Used for: Initial code skeleton and test suggestions; final implementation and tests were reviewed and edited by me.
-->

[manzoorwanijk]

Thanks for the PR! Can you expose which AI tool do you use in PR?

Updated. Thanks