JavaScript strings potx does not find: trailing commas, null arguments, template literals

Problem/Motivation

potx extracts Drupal.t() and Drupal.formatPlural() calls of JavaScript with regular expressions. These forms of the calls are reported as faulty or not seen, and their strings are not in the templates:

1. A trailing comma after the last argument. Core's JavaScript is formatted with a trailing comma in multi-line calls:

   Drupal.t(
     'Changes made in this table will not be saved until the form is submitted.',
   );

   The expressions allow a comma after the options only. In a copy of the localize.drupal.org database (to February 2024), such strings of core have lines in every release up to 9.5.11 and 10.0.0-alpha7, and in none of the later Drupal 10 releases, to 10.2.3; the translations of these releases do not have them (checked: "An AJAX HTTP request terminated abnormally.", "Changes made in this table will not be saved until the form is submitted.", "Remove group", "This permission is inherited from the authenticated user role.").

2. null in place of the arguments, with options: Drupal.t('…', null, {context: '…'}). The expressions require an object before the options.
3. Template literals without substitutions: Drupal.t(`The following files could not be loaded: @dependencies`, {…}). The expressions know single and double quotes only. A template literal with ${…} is not a literal string, and it is reported as before.

Strings of a corpus of 51 projects

Drupal 11.4.9 core with its recipes, 33 contrib projects of localize.drupal.org, Drupal 7 core and contrib, potx's own fixtures. Of the 48 faulty JavaScript calls reported for Drupal 11 core, 4 are left, all real: a call with variables in misc/drupal.js, two template literals with ${} in the CKEditor 5 media plugin (source and build), a call in a comment of misc/announce.js.

1. Trailing commas: 26 new source strings of Drupal 11 core, 4 strings in more files, 1 new source string of l10n_server.

2. null arguments: 2 new source strings of Drupal 11 core, modules/ckeditor5/js/ckeditor5.admin.js, with their contexts:

• "The toolbar buttons that don't fit the user's browser window width will be grouped in a dropdown. …" (context: CKEditor 5 toolbar help text, default, no explicit wrapping breakpoint)
• "You have configured a multi-row toolbar by using an explicit wrapping breakpoint. …" (context: CKEditor 5 toolbar help text, with explicit wrapping breakpoint)

3. Template literals: 2 new source strings of Drupal 11 core:

• "The following files could not be loaded: @dependencies" (misc/ajax.js, misc/htmx/htmx-utils.js)
• "@listType button @label" (modules/ckeditor5/js/ckeditor5.admin.js)

Proposed resolution

One commit for each, with a test in JsExtractorTest:

1. The expressions allow a comma after the string of Drupal.t() and the plural of Drupal.formatPlural().
2. The expressions allow null in place of the arguments.
3. The strings of the expressions are also template literals without ${, with the escapes of a double-quoted string.

LLM disclosure

LLM was used to find, diagnose explain and fix this issue. With human review.