feat(wip): allow private hooks calls

Signed-off-by: Bart Jaskulski <bjaskulski@protonmail.com>

src/HooksTrait.php

+<?php
+declare( strict_types=1 );
+
+namespace WPDesk\Init;
+
+/**
+ * Hooks trait.
+ *
+ * Allows protected and private methods to be used as hook callbacks in PHP <8.1. Since PHP 8.1
+ * you are able to take advantage of first class callable and register private methods in hooks
+ * without any workarounds.
+ *
+ * @author  John P. Bloch
+ * @link    https://github.com/johnpbloch/wordpress-dev/blob/master/src/Hooks.php
+ */
+trait HooksTrait {
+
+	/**
+	 * Add a WordPress filter.
+	 *
+	 * @param callable $method
+	 *
+	 * @return true
+	 */
+	protected function add_filter(
+		string $hook,
+		$method,
+		int $priority = 10,
+		int $arg_count = 1
+	): bool {
+		return add_filter(
+			$hook,
+			$this->map_filter( $method, $arg_count ),
+			$priority,
+			$arg_count
+		);
+	}
+
+	/**
+	 * Add a WordPress action.
+	 *
+	 * This is an alias of add_filter().
+	 *
+	 * @param callable $method
+	 *
+	 * @return true
+	 */
+	protected function add_action( string $hook, $method, int $priority = 10, int $arg_count = 1 ): bool {
+		return $this->add_filter( $hook, $method, $priority, $arg_count );
+	}
+
+	/**
+	 * Remove a WordPress filter.
+	 *
+	 * @param callable $method
+	 *
+	 * @return bool Whether the function existed before it was removed.
+	 */
+	protected function remove_filter(
+		string $hook,
+		$method,
+		int $priority = 10,
+		int $arg_count = 1
+	): bool {
+		return remove_filter(
+			$hook,
+			$this->map_filter( $method, $arg_count ),
+			$priority
+		);
+	}
+
+	/**
+	 * Remove a WordPress action.
+	 *
+	 * This is an alias of remove_filter().
+	 *
+	 * @param callable $method
+	 *
+	 * @return bool Whether the function is removed.
+	 */
+	protected function remove_action(
+		string $hook,
+		$method,
+		int $priority = 10,
+		int $arg_count = 1
+	): bool {
+		return $this->remove_filter( $hook, $method, $priority, $arg_count );
+	}
+
+	/**
+	 * Map a filter to a closure that inherits the class' internal scope.
+	 *
+	 * This allows hooks to use protected and private methods.
+	 *
+	 * @param string $callable
+	 * @param int $arg_count
+	 *
+	 * @return \Closure The callable actually attached to a WP hook
+	 */
+	private function map_filter( $callable, int $arg_count ): \Closure {
+		if ( is_string( $callable ) && method_exists( $this, $callable ) ) {
+			$object = $this;
+			$method = $callable;
+		}
+
+		if ( is_array( $callable ) ) {
+			[ $object, $method ] = $callable;
+		}
+
+		return static function () use ( $object, $method, $arg_count ) {
+			return $object->{$method}( ...array_slice( func_get_args(), 0, $arg_count ) );
+		};
+	}
+}

tests/HooksTraitTest.php

+<?php
+declare( strict_types=1 );
+
+namespace WPDesk\Init\Tests;
+
+class HooksTraitTest extends \PHPUnit\Framework\TestCase {
+
+	/**
+	 * How you can call a hook:
+	 * 1. callable string: '__return_true'
+	 * 2. closure: function () { echo "hello"; }
+	 * 3. static call: [stdClass::class, 'hello']
+	 * 4. class instance call: [ $this, 'hello' ]
+	 * 5. invokable object: $this
+	 * ! Since PHP 8.1
+	 * 6. first-class callable: __return_true(...), $this->hello(...)
+	 */
+
+}
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