Add native block-editor support

• Add wp-scripts for build
• Enqueue script, excluding it from widget block editor
• Localize script with configurable/filterable options
• Localize script with titles for post types to match current functionality
• Register meta and set sanitization callbacks
• Allow meta to be accessed via endpoint
• Create sidebar plugin to show the two fields used by the plugin

tests/test-class-external-permalinks-redux-block-editor.php

+<?php
+/**
+ * Test block-editor integration.
+ *
+ * @package External_Permalinks_Redux
+ */
+
+/**
+ * Class TestClassExternalPermalinksReduxBlockEditor.
+ *
+ * @coversDefaultClass External_Permalinks_Redux_Block_Editor
+ */
+class TestClassExternalPermalinksReduxBlockEditor extends WP_UnitTestCase {
+	/**
+	 * Test meta registration.
+	 *
+	 * @covers ::register_meta()
+	 */
+	public function test_register_meta() {
+		global $wp_meta_keys;
+
+		$wp_meta_keys = null;
+
+		$this->assertFalse(
+			registered_meta_key_exists(
+				'post',
+				external_permalinks_redux::get_instance()->meta_key_target
+			),
+			'Failed to assert that "target" meta key is not registered.'
+		);
+
+		$this->assertFalse(
+			registered_meta_key_exists(
+				'post',
+				external_permalinks_redux::get_instance()->meta_key_type
+			),
+			'Failed to assert that "type" meta key is not registered.'
+		);
+
+		External_Permalinks_Redux_Block_Editor::get_instance()->register_meta();
+
+		$this->assertTrue(
+			registered_meta_key_exists(
+				'post',
+				external_permalinks_redux::get_instance()->meta_key_target
+			),
+			'Failed to assert that "target" meta key is registered.'
+		);
+
+		$this->assertTrue(
+			registered_meta_key_exists(
+				'post',
+				external_permalinks_redux::get_instance()->meta_key_type
+			),
+			'Failed to assert that "type" meta key is registered.'
+		);
+	}
+
+	/**
+	 * Test overridding private meta editing.
+	 *
+	 * @covers ::allow_meta_updates()
+	 */
+	public function test_allow_meta_updates() {
+		$this->assertTrue(
+			External_Permalinks_Redux_Block_Editor::get_instance()->allow_meta_updates(
+				true,
+				'_a_random_key',
+				'term'
+			),
+			'Failed to assert that a term\'s key is not modified..'
+		);
+
+		$this->assertTrue(
+			External_Permalinks_Redux_Block_Editor::get_instance()->allow_meta_updates(
+				true,
+				'_a_random_key',
+				'post'
+			),
+			'Failed to assert that unrelated key\'s protection is not modified.'
+		);
+
+		$this->assertFalse(
+			External_Permalinks_Redux_Block_Editor::get_instance()->allow_meta_updates(
+				true,
+				external_permalinks_redux::get_instance()->meta_key_target,
+				'post'
+			),
+			'Failed to assert that "target" key is not protected.'
+		);
+
+		$this->assertFalse(
+			External_Permalinks_Redux_Block_Editor::get_instance()->allow_meta_updates(
+				true,
+				external_permalinks_redux::get_instance()->meta_key_type,
+				'post'
+			),
+			'Failed to assert that "type" key is not protected.'
+		);
+	}
+
+	/**
+	 * Test script enqueueing.
+	 *
+	 * @covers ::enqueue()
+	 */
+	public function test_enqueue() {
+		$asset_handle = 'external-permalinks-redux';
+
+		$this->assertFalse(
+			wp_script_is( $asset_handle, 'enqueued' ),
+			'Failed to assert that script is not enqueued.'
+		);
+
+		remove_all_actions( 'admin_init' );
+		do_action( 'admin_init' );
+		external_permalinks_redux::get_instance()->action_admin_init();
+		External_Permalinks_Redux_Block_Editor::get_instance()->enqueue();
+
+		$this->assertTrue(
+			wp_script_is( $asset_handle, 'enqueued' ),
+			'Failed to assert that script is enqueued.'
+		);
+
+		$this->assertStringContainsString(
+			'externalPermalinksReduxConfig',
+			wp_scripts()->get_data( $asset_handle, 'data' ),
+			'Failed to assert that configuration data is added.'
+		);
+	}
+
+	/**
+	 * Test conversion of status codes to format expected by Gutenberg's
+	 * `SelectControl` component.
+	 *
+	 * @covers ::_get_status_codes()
+	 */
+	public function test__get_status_codes() {
+		$class      = External_Permalinks_Redux_Block_Editor::get_instance();
+		$reflection = new ReflectionClass( $class );
+
+		$method = $reflection->getMethod( '_get_status_codes' );
+		$method->setAccessible( true );
+
+		remove_all_actions( 'admin_init' );
+		do_action( 'admin_init' );
+		external_permalinks_redux::get_instance()->action_admin_init();
+
+		$this->assertEquals(
+			array(
+				array(
+					'label' => '-- Select --',
+					'value' => 0,
+				),
+				array(
+					'label' => 'Temporary (302)',
+					'value' => 302,
+				),
+				array(
+					'label' => 'Permanent (301)',
+					'value' => 301,
+				),
+			),
+			$method->invoke( $class ),
+			'Failed to assert that status codes are transformed as expected.'
+		);
+	}
+}