Add shortcut methods for the LegacyProxy in the WooCommerce class.

The following methods are added and can be invoked using `WC()`,
they just redirect to the same methods in LegacyProxy:

call_function
call_static
get_instance_of

includes/class-woocommerce.php

@@ -8,6 +8,8 @@
 
 defined( 'ABSPATH' ) || exit;
 
+use Automattic\WooCommerce\Proxies\LegacyProxy;
+
 /**
  * Main WooCommerce Class.
  *
@@ -902,4 +904,51 @@ final class WooCommerce {
 	public function is_wc_admin_active() {
 		return function_exists( 'wc_admin_url' );
 	}
+
+	/**
+	 * Call a user function. This should be used to execute any non-idempotent function, especially
+	 * those in the `includes` directory or provided by WordPress.
+	 *
+	 * @param string $function_name The function to execute.
+	 * @param mixed  ...$parameters The parameters to pass to the function.
+	 *
+	 * @return mixed The result from the function.
+	 *
+	 * @since 4.4
+	 */
+	public function call_function( $function_name, ...$parameters ) {
+		return wc_get_container()->get( LegacyProxy::class )->call_function( $function_name, ...$parameters );
+	}
+
+	/**
+	 * Call a static method in a class. This should be used to execute any non-idempotent method in classes
+	 * from the `includes` directory.
+	 *
+	 * @param string $class_name The name of the class containing the method.
+	 * @param string $method_name The name of the method.
+	 * @param mixed  ...$parameters The parameters to pass to the method.
+	 *
+	 * @return mixed The result from the method.
+	 *
+	 * @since 4.4
+	 */
+	public function call_static( $class_name, $method_name, ...$parameters ) {
+		return wc_get_container()->get( LegacyProxy::class )->call_static( $class_name, $method_name, ...$parameters );
+	}
+
+	/**
+	 * Gets an instance of a given legacy class.
+	 * This must not be used to get instances of classes in the `src` directory.
+	 *
+	 * @param string $class_name The name of the class to get an instance for.
+	 * @param mixed  ...$args Parameters to be passed to the class constructor or to the appropriate internal 'get_instance_of_' method.
+	 *
+	 * @return object The instance of the class.
+	 * @throws \Exception The requested class belongs to the `src` directory, or there was an error creating an instance of the class.
+	 *
+	 * @since 4.4
+	 */
+	public function get_instance_of( string $class_name, ...$args ) {
+		return wc_get_container()->get( LegacyProxy::class )->get_instance_of( $class_name, ...$args );
+	}
 }

tests/php/src/Proxies/ClassThatDependsOnLegacyCodeTest.php

@@ -0,0 +1,128 @@
+<?php
+/**
+ * ClassThatDependsOnLegacyCodeTest class file
+ *
+ * @package Automattic\WooCommerce\Tests\Proxies
+ */
+
+namespace Automattic\WooCommerce\Tests\Proxies;
+
+use Automattic\WooCommerce\Proxies\LegacyProxy;
+use Automattic\WooCommerce\Tests\Proxies\ExampleClasses\ClassThatDependsOnLegacyCode;
+use Automattic\WooCommerce\Tests\Internal\DependencyManagement\ExampleClasses\DependencyClass;
+
+/**
+ * Tests for a class that depends on legacy code
+ */
+class ClassThatDependsOnLegacyCodeTest extends \WC_Unit_Test_Case {
+	/**
+	 * The system under test.
+	 *
+	 * @var LegacyProxy
+	 */
+	private $sut;
+
+	/**
+	 * Runs before each test.
+	 */
+	public function setUp() {
+		$container = wc_get_container();
+		$container->add( ClassThatDependsOnLegacyCode::class )->addArgument( LegacyProxy::class );
+		$this->sut = $container->get( ClassThatDependsOnLegacyCode::class );
+	}
+
+	/**
+	 * Legacy proxy's 'call_function' can be used from both an injected LegacyProxy and from 'WC()->call_function'
+	 *
+	 * @param string $method_to_use Method in the tested class to use.
+	 *
+	 * @testWith ["call_legacy_function_using_injected_proxy"]
+	 *           ["call_legacy_function_using_woocommerce_class"]
+	 */
+	public function test_call_function_can_be_invoked_via_injected_legacy_proxy_and_woocommerce_object( $method_to_use ) {
+		$this->assertEquals( 255, $this->sut->$method_to_use( 'hexdec', 'FF' ) );
+	}
+
+	/**
+	 * Function mocks can be used from both an injected LegacyProxy and from 'WC()->call_function'
+	 *
+	 * @param string $method_to_use Method in the tested class to use.
+	 *
+	 * @testWith ["call_legacy_function_using_injected_proxy"]
+	 *           ["call_legacy_function_using_woocommerce_class"]
+	 */
+	public function test_function_mocks_can_be_used_via_injected_legacy_proxy_and_woocommerce_object( $method_to_use ) {
+		$this->register_legacy_proxy_function_mocks(
+			array(
+				'hexdec' => function( $hex_string ) {
+					return "Mocked hexdec for $hex_string";
+				},
+			)
+		);
+		$this->assertEquals( 'Mocked hexdec for FF', $this->sut->$method_to_use( 'hexdec', 'FF' ) );
+	}
+
+	/**
+	 * Legacy proxy's 'call_static' can be used from both an injected LegacyProxy and from 'WC()->call_function'
+	 *
+	 * @param string $method_to_use Method in the tested class to use.
+	 *
+	 * @testWith ["call_static_method_using_injected_proxy"]
+	 *           ["call_static_method_using_woocommerce_class"]
+	 */
+	public function test_call_static_can_be_invoked_via_injected_legacy_proxy_and_woocommerce_object( $method_to_use ) {
+		$result = $this->sut->$method_to_use( DependencyClass::class, 'concat', 'foo', 'bar', 'fizz' );
+		$this->assertEquals( 'Parts: foo, bar, fizz', $result );
+	}
+
+	/**
+	 * Static method mocks can be used from both an injected LegacyProxy and from 'WC()->call_function'
+	 *
+	 * @param string $method_to_use Method in the tested class to use.
+	 *
+	 * @testWith ["call_static_method_using_injected_proxy"]
+	 *           ["call_static_method_using_woocommerce_class"]
+	 */
+	public function test_static_mocks_can_be_used_via_injected_legacy_proxy_and_woocommerce_object( $method_to_use ) {
+		$this->register_legacy_proxy_static_mocks(
+			array(
+				DependencyClass::class => array(
+					'concat' => function( ...$parts ) {
+						return "I'm returning concat of these parts: " . join( ' ', $parts );
+					},
+				),
+			)
+		);
+
+		$expected = "I'm returning concat of these parts: foo bar fizz";
+		$result   = $this->sut->$method_to_use( DependencyClass::class, 'concat', 'foo', 'bar', 'fizz' );
+		$this->assertEquals( $expected, $result );
+	}
+
+	/**
+	 * Legacy proxy's 'get_instance_of' can be used from both an injected LegacyProxy and from 'WC()->call_function'
+	 *
+	 * @param string $method_to_use Method in the tested class to use.
+	 *
+	 * @testWith ["get_instance_of_using_injected_proxy"]
+	 *           ["get_instance_of_using_woocommerce_class"]
+	 */
+	public function test_get_instance_of_can_be_used_via_injected_legacy_proxy_and_woocommerce_object( $method_to_use ) {
+		$instance = $this->sut->$method_to_use( \WC_Queue_Interface::class, 34 );
+		$this->assertInstanceOf( \WC_Action_Queue::class, $instance );
+	}
+
+	/**
+	 * Legacy object mocks can be used from both an injected LegacyProxy and from 'WC()->call_function'
+	 *
+	 * @param string $method_to_use Method in the tested class to use.
+	 *
+	 * @testWith ["get_instance_of_using_injected_proxy"]
+	 *           ["get_instance_of_using_woocommerce_class"]
+	 */
+	public function test_class_mocks_can_be_used_via_injected_legacy_proxy_and_woocommerce_object( $method_to_use ) {
+		$mock = new \stdClass();
+		$this->register_legacy_proxy_class_mocks( array( \WC_Query::class => $mock ) );
+		$this->assertSame( $mock, $this->sut->$method_to_use( \WC_Query::class ) );
+	}
+}

tests/php/src/Proxies/ExampleClasses/ClassThatDependsOnLegacyCode.php

@@ -0,0 +1,105 @@
+<?php
+/**
+ * ClassThatDependsOnLegacyCode class file
+ *
+ * @package Automattic\WooCommerce\Tests\Proxies\ExampleClasses
+ */
+
+namespace Automattic\WooCommerce\Tests\Proxies\ExampleClasses;
+
+use Automattic\WooCommerce\Proxies\LegacyProxy;
+
+/**
+ * An example class that uses the legacy proxy both from an constructor injected proxy and from the helper methods in the WooCommerce class.
+ */
+class ClassThatDependsOnLegacyCode {
+	/**
+	 * The injected LegacyProxy.
+	 *
+	 * @var LegacyProxy
+	 */
+	private $legacy_proxy;
+
+	/**
+	 * Class constructor.
+	 *
+	 * @param LegacyProxy $legacy_proxy The instance of LegacyProxy to use.
+	 */
+	public function __construct( LegacyProxy $legacy_proxy ) {
+		$this->legacy_proxy = $legacy_proxy;
+	}
+
+	/**
+	 * Use proxy's 'call_function' from the injected proxy.
+	 *
+	 * @param string $function Function to call.
+	 * @param mixed  ...$parameters Parameters to pass to the function.
+	 *
+	 * @return mixed The result from the function.
+	 */
+	public function call_legacy_function_using_injected_proxy( $function, ...$parameters ) {
+		return $this->legacy_proxy->call_function( $function, ...$parameters );
+	}
+
+	/**
+	 * Use proxy's 'call_function' using 'WC()->call_function'.
+	 *
+	 * @param string $function Function to call.
+	 * @param mixed  ...$parameters Parameters to pass to the function.
+	 *
+	 * @return mixed The result from the function.
+	 */
+	public function call_legacy_function_using_woocommerce_class( $function, ...$parameters ) {
+		return WC()->call_function( $function, ...$parameters );
+	}
+
+	/**
+	 * Use proxy's 'call_static' from the injected proxy.
+	 *
+	 * @param string $class_name Class containing the static method to call.
+	 * @param string $method_name Static method to call.
+	 * @param mixed  ...$parameters Parameters to pass to the method.
+	 *
+	 * @return mixed The result from the method.
+	 */
+	public function call_static_method_using_injected_proxy( $class_name, $method_name, ...$parameters ) {
+		return $this->legacy_proxy->call_static( $class_name, $method_name, ...$parameters );
+	}
+
+	/**
+	 * Use proxy's 'call_static' using 'WC()->call_function'.
+	 *
+	 * @param string $class_name Class containing the static method to call.
+	 * @param string $method_name Static method to call.
+	 * @param mixed  ...$parameters Parameters to pass to the method.
+	 *
+	 * @return mixed The result from the method.
+	 */
+	public function call_static_method_using_woocommerce_class( $class_name, $method_name, ...$parameters ) {
+		return WC()->call_static( $class_name, $method_name, ...$parameters );
+	}
+
+	/**
+	 * Use proxy's 'get_instance_of' from the injected proxy.
+	 *
+	 * @param string $class_name The name of the class to get an instance of.
+	 * @param mixed  ...$args Extra arguments for 'get_instance_of'.
+	 *
+	 * @return object The instance obtained.
+	 */
+	public function get_instance_of_using_injected_proxy( string $class_name, ...$args ) {
+		return $this->legacy_proxy->get_instance_of( $class_name, ...$args );
+	}
+
+	/**
+	 * Use proxy's 'get_instance_of' using 'WC()->call_function'.
+	 *
+	 * @param string $class_name The name of the class to get an instance of.
+	 * @param mixed  ...$args Extra arguments for 'get_instance_of'.
+	 *
+	 * @return object The instance obtained.
+	 */
+	public function get_instance_of_using_woocommerce_class( string $class_name, ...$args ) {
+		return WC()->get_instance_of( $class_name, ...$args );
+	}
+}