Gettext Scanner Gulp 4 Script for Twig Projects

gulpfile.js

/**
 * Gettext Scanner Script for Twig Projects
 * v1.3
 * 
 * Developed by Luís Silva
 * https://github.com/luism-s
 */

/**
 * Purpose:
 * Scan Twig and PHP files in the given directories for gettext function calls and output a POT file for translation. 
 *
 * Description:
 * While working with Wordpress using the Twig template engine, one might find easier to use gettext 
 * functions in .twig files for string translation. To simplify the scanning of .twig files for those same functions, this 
 * script was built to parse .twig files, wrap occurrences of gettext function calls in php tags and 
 * output the result as a .php file and from that generate a POT file.
 * It also scans PHP files as well.
 *
 * Context: https://github.com/timber/timber/issues/1465
 * 
 * Usage: `gulp pot`
 *
 * Logic:
 * - Iterates over all given .twig files
 * - Search and replace for gettext functions in Twig files and wraps them around PHP tags
 * - Outputs each file as .php into a cache folder
 * - Scan all .php files for gettext functions using 'gulp-wp-pot' (cache included)
 * - Generate .pot file
 * 
 * Dependencies:
 * `npm install gulp gulp-if del gulp-wp-pot gulp-replace gulp-rename`
 * 
 * Warning:
 * This script has only ben tested in the context of Wordpress theme development using Timber.
 * 
 * TODO:
 * Cover `translate_nooped_plural` function.
 */
const gulp = require('gulp');
const gulpif = require('gulp-if');
const del = require('del');
const wpPot = require('gulp-wp-pot');
const replace = require('gulp-replace');
const rename = require('gulp-rename');

/**
 * Configuration Options
 * 
 * All paths are as if this script is 
 * located in the root of the theme and all the Twig
 * files are located under /views
 */
const config = {
  "text_domain" : "theme-test",       // Replace with your domain
  "twig_files"  : "views/**/*.twig",  // Twig Files
  "php_files"   : "**/*.php",         // PHP Files
  "cacheFolder" : "views/cache",      // Cache Folder
  "destFolder"  : "languages",        // Folder where .pot file will be saved
  "keepCache"   : true                // Delete cache files after script finishes
};


/**
 * __
 * _e
 * _x
 * _xn
 * _ex
 * _n_noop
 * _nx_noop
 * translate  -> Match __,  _e, _x and so on
 * \(         -> Match (
 * \s*?       -> Match empty space 0 or infinite times, as few times as possible (ungreedy)
 * ['"]     -> Match ' or "
 * .+?        -> Match any character, 1 to infinite times, as few times as possible (ungreedy)
 * ,          -> Match ,
 * .+?        -> Match any character, 1 to infinite times, as few times as possible (ungreedy)
 * \)         -> Match )
 */
const gettext_regex = {

  // _e( "text", "domain" )
  // __( "text", "domain" )
  // translate( "text", "domain" )
  // esc_attr__( "text", "domain" )
  // esc_attr_e( "text", "domain" )
  // esc_html__( "text", "domain" )
  // esc_html_e( "text", "domain" )
  simple: /(__|_e|translate|esc_attr__|esc_attr_e|esc_html__|esc_html_e)\(\s*?['"].+?['"]\s*?,\s*?['"].+?['"]\s*?\)/g,

  // _n( "single", "plural", number, "domain" )
  plural: /_n\(\s*?['"].*?['"]\s*?,\s*?['"].*?['"]\s*?,\s*?.+?\s*?,\s*?['"].+?['"]\s*?\)/g,

  // _x( "text", "context", "domain" )
  // _ex( "text", "context", "domain" )
  // esc_attr_x( "text", "context", "domain" )
  // esc_html_x( "text", "context", "domain" )
  // _nx( "single", "plural", "number", "context", "domain" )
  disambiguation: /(_x|_ex|_nx|esc_attr_x|esc_html_x)\(\s*?['"].+?['"]\s*?,\s*?['"].+?['"]\s*?,\s*?['"].+?['"]\s*?\)/g,

  // _n_noop( "singular", "plural", "domain" )
  // _nx_noop( "singular", "plural", "context", "domain" )
  noop: /(_n_noop|_nx_noop)\((\s*?['"].+?['"]\s*?),(\s*?['"]\w+?['"]\s*?,){0,1}\s*?['"].+?['"]\s*?\)/g,
};

/**
 * Main Task
 */
gulp.task('pot', gulp.series(['compile-twigs', 'generate-pot']));

/**
 * Generate POT file from all .php files in the theme,
 * including the cache folder.
 */
gulp.task('generate-pot', () => {
  const output = gulp.src(config.php_files)
    .pipe(wpPot({
      domain: config.text_domain
    }))
    .pipe(gulp.dest(`${config.destFolder}/${config.text_domain}.pot`))
    .pipe(gulpif(!config.keepCache, del.bind(null, [config.cacheFolder], { force: true })));
  return output;
});

/**
 * Fake Twig Gettext Compiler
 * 
 * Searches and replaces all occurences of __('string', 'domain'), _e('string', 'domain') and so on,
 * with <?php __('string', 'domain'); ?> or <?php _e('string', 'domain'); ?> and saves the content
 * in a .php file with the same name in the cache folder.
 * 
 * Functions supported:
 * 
 * Simple: __(), _e(), translate()
 * Plural: _n()
 * Disambiguation: _x(), _ex(), _nx()
 * Noop: _n_loop(), _nx_noop()
 */
gulp.task('compile-twigs', () => {
  del.bind(null, [config.cacheFolder], {force: true})
  // Iterate over .twig files
  const output = gulp.src(config.twig_files)
    // Search for Gettext function calls and wrap them around PHP tags. 
    .pipe(replace(gettext_regex.simple, match => `<?php ${match}; ?>`))
    .pipe(replace(gettext_regex.plural, match => `<?php ${match}; ?>`))
    .pipe(replace(gettext_regex.disambiguation, match => `<?php ${match}; ?>`))
    .pipe(replace(gettext_regex.noop, match => `<?php ${match}; ?>`))
    // Rename file with .php extension
    .pipe(rename({
      extname: '.php',
    }))
    // Output the result to the cache folder as a .php file.
    .pipe(gulp.dest(config.cacheFolder));
  
   return output;
});

package.json

{
  "name": "twig-gettext-pot-parser",
  "version": "1.2.0",
  "dependencies": {
    "gulp": "3.9.1",
    "del": "^3.0.0",
    "gulp-if": "^2.0.2",
    "gulp-rename": "^1.2.2",
    "gulp-replace": "^0.6.1",
    "gulp-wp-pot": "^2.2.0",
  },
  "scripts": {
    "twig-pot": "gulp pot"
  }
}

twig-gettext.php

<?php
/**
 * Include Wordpress gettext functions in Twig if necessary
 */

// Init twig engine
global $twig;
$loader = new Twig_Loader_Filesystem( '/views' );
$twig = new Twig_Environment( $loader, [] );

// Add wordpress gettext functions
$twig->addFunction(new Twig_SimpleFunction('__', function( $text, $domain = 'default' ) {
  return __($text, $domain);
} ));
$twig->addFunction(new Twig_SimpleFunction('_n', function( $single, $plural, $number, $domain = 'default' ) {
  return _n($single, $plural, $number, $domain);
} ));
$twig->addFunction(new Twig_SimpleFunction('_x', function( $text, $context, $domain = 'default' ) {
  return _x($text, $context, $domain);
} ));
$twig->addFunction(new Twig_SimpleFunction('_ex', function( $text, $context, $domain = 'default' ) {
  return _ex($text, $context, $domain);
} ));
$twig->addFunction(new Twig_SimpleFunction('_nx', function( $single, $plural, $number, $context, $domain = 'default' ) {
  return _nx($single, $plural, $number, $context, $domain);
} ));