Support callables to provide the localization data

README.md

@@ -31,6 +31,7 @@ A library for managing asset registration and enqueuing in WordPress.
   * [Conditional enqueuing](#conditional-enqueuing)
   * [Firing a callback after enqueuing occurs](#firing-a-callback-after-enqueuing-occurs)
   * [Output JS data](#output-js-data)
+	  * [Using a callable to provide localization data](#using-a-callable-to-provide-localization-data)
   * [Output content before/after a JS asset is output](#output-content-beforeafter-a-js-asset-is-output)
   * [Style meta data](#style-meta-data)
 
@@ -500,6 +501,28 @@ Note the `my-second-script-mod` handle is overriding a specific nested
 key, `boomshakalaka.project.secondScriptData.animal`, in the `boomshakalaka.project.secondScriptData` object while
 preserving the other keys.
 
+#### Using a callable to provide localization data
+
+If you need to provide localization data dynamically, you can use a callable to do so. The callable will be called
+when the asset is enqueued and the return value will be used. The callable will be passed the asset as the first
+argument and should return an array.
+
+```php
+Asset::add( 'my-script', 'js/some-asset.js' )
+	->add_localize_script(
+		'boomshakalaka.project.myScriptData',
+		function( Asset $asset ) {
+			return [
+				'animal' => 'cat',
+				'color'  => 'orange',
+			];
+		}
+	)
+	->register();
+```
+
+Any valid callable can be used, including Closures, like in the example above.
+
 ### Output content before/after a JS asset is output
 
 There may be times when you wish to output markup or text immediately before or immediately after outputting the JS

src/Assets/Asset.php

@@ -414,11 +414,13 @@ public function call_after_enqueue( $callable ) {
 	 * @since 1.0.0
 	 *
 	 * @param string $object_name JS object name.
-	 * @param array  $data        Data assigned to the JS object.
+	 * @param array|callable  $data Data assigned to the JS object. If a callable is passed, it will be called
+	 *                              when the asset is enqueued and the return value will be used. The callable
+	 *                              will be passed the asset as the first argument and should return an array.
 	 *
 	 * @return static
 	 */
-	public function add_localize_script( string $object_name, array $data ) {
+	public function add_localize_script( string $object_name, $data ) {
 		if ( str_contains( $object_name, '.' ) ) {
 			$this->custom_localize_script_objects[] = [ $object_name, $data ];
 		} else {

src/Assets/Assets.php

@@ -357,7 +357,7 @@ public function filter_add_localization_data( $tag, $handle ) {
 
 				// If we have a Callable as the Localize data we execute it.
 				if ( is_callable( $localize ) ) {
-					$localize = call_user_func( $localize, $asset );
+					$localize = $localize( $asset );
 				}
 
 				wp_localize_script( $asset->get_slug(), $key, $localize );
@@ -378,6 +378,11 @@ public function filter_add_localization_data( $tag, $handle ) {
 		 * Print the dot.notation namespaced objects for the asset.
 		 */
 		foreach ( $custom_localize_scripts as [$object_name, $data] ) {
+			// If we have a Callable as the Localize data we execute it.
+			if ( is_callable( $data ) ) {
+				$data = $data( $asset );
+			}
+
 			$localized_key = "{$asset->get_slug()}::{$object_name}";
 
 			if ( in_array( $localized_key, $this->localized, true ) ) {

tests/wpunit/AssetsTest.php

@@ -215,4 +215,55 @@ public function should_allow_localizing_data_in_normal_and_namespaced_form_for_s
 			$apply_filters
 		);
 	}
+
+	/**
+	 * It should allow localizing data using a Closure
+	 *
+	 * @test
+	 */
+	public function should_allow_localizing_data_using_a_closure(): void {
+		$resolved_one      = false;
+		$resolved_two      = false;
+		$data_callback_one = function () use ( &$resolved_one ) {
+			$resolved_one = true;
+
+			return [
+				'animal' => 'cat',
+				'color'  => 'orange',
+			];
+		};
+		$data_callback_two = function () use ( &$resolved_two ) {
+			$resolved_two = true;
+
+			return [
+				'animal' => 'dog',
+				'color'  => 'green',
+			];
+		};
+
+		Asset::add( 'my-script-with-closure-data', 'test-script.js' )
+		     ->add_localize_script( 'scriptWithClosureData', $data_callback_one )
+		     ->add_localize_script( 'acme.project.closureData', $data_callback_two )
+		     ->register();
+
+		$this->assertFalse( $resolved_one, 'The first callback should not have been resolved yet.' );
+		$this->assertFalse( $resolved_two, 'The second callback should not have been resolved yet.' );
+
+		$apply_filters = apply_filters( 'script_loader_tag', '', 'my-script-with-closure-data' );
+		$this->assertEquals( <<< SCRIPT
+<script id="my-script-with-closure-data-js-extra">
+var scriptWithClosureData = {"animal":"cat","color":"orange"};
+</script>
+<script id="my-script-with-closure-data-ns-extra">
+window.acme = window.acme || {};
+window.acme.project = window.acme.project || {};
+window.acme.project.closureData = Object.assign(window.acme.project.closureData || {}, {"animal":"dog","color":"green"});
+</script>
+SCRIPT,
+			$apply_filters
+		);
+
+		$this->assertTrue( $resolved_one );
+		$this->assertTrue( $resolved_two );
+	}
 }