Add --importer argument to specify alternative importer class

features/import.feature

@@ -400,3 +400,61 @@ Feature: Import content.
       https://newsite.com/
       """
 
+  @require-wp-5.2 @require-mysql
+  Scenario: Specifying a non-existent importer class produces an error
+    Given a WP install
+    And I run `wp plugin install wordpress-importer --activate`
+
+    When I run `wp export`
+    Then save STDOUT 'Writing to file %s' as {EXPORT_FILE}
+
+    When I try `wp import {EXPORT_FILE} --authors=skip --importer=NonExistentImporterClass`
+    Then STDERR should contain:
+      """
+      Error: Importer class 'NonExistentImporterClass' does not exist.
+      """
+    And the return code should be 1
+
+  @require-wp-5.2 @require-mysql
+  Scenario: Specifying an importer class that is not a subclass of WP_Import produces an error
+    Given a WP install
+    And I run `wp plugin install wordpress-importer --activate`
+
+    When I run `wp export`
+    Then save STDOUT 'Writing to file %s' as {EXPORT_FILE}
+
+    When I try `wp import {EXPORT_FILE} --authors=skip --importer=WP_CLI_Command`
+    Then STDERR should contain:
+      """
+      Error: Importer class 'WP_CLI_Command' must be a subclass of WP_Import.
+      """
+    And the return code should be 1
+
+  @require-wp-5.2 @require-mysql
+  Scenario: Specifying a valid custom importer subclass succeeds
+    Given a WP install
+    And I run `wp plugin install wordpress-importer --activate`
+    And a wp-content/mu-plugins/custom-importer.php file:
+      """
+      <?php
+      if ( ! class_exists( 'WP_Importer' ) ) {
+        require_once ABSPATH . 'wp-admin/includes/class-wp-importer.php';
+      }
+
+      if ( ! class_exists( 'WP_Import' ) ) {
+        require_once WP_PLUGIN_DIR . '/wordpress-importer/class-wp-import.php';
+      }
+
+      class My_Custom_WP_Import extends WP_Import {}
+      """
+
+    When I run `wp export`
+    Then save STDOUT 'Writing to file %s' as {EXPORT_FILE}
+
+    When I run `wp site empty --yes`
+    Then STDOUT should not be empty
+
+    When I run `wp import {EXPORT_FILE} --authors=skip --importer=My_Custom_WP_Import`
+    Then STDOUT should not be empty
+    And STDERR should be empty
+

src/Import_Command.php

@@ -29,6 +29,9 @@ class Import_Command extends WP_CLI_Command {
 	 * : Change all imported URLs that currently link to the previous site so that they now link to this site
 	 * Requires WordPress Importer version 0.9.1 or newer.
 	 *
+	 * [--importer=<importer>]
+	 * : Use a custom importer class instead of the default WP_Import. The class must exist and be a subclass of WP_Import.
+	 *
 	 * ## EXAMPLES
 	 *
 	 *     # Import content from a WXR file
@@ -45,6 +48,7 @@ public function __invoke( $args, $assoc_args ) {
 			'authors'      => null,
 			'skip'         => [],
 			'rewrite_urls' => null,
+			'importer'     => 'WP_Import',
 		);
 		$assoc_args = wp_parse_args( $assoc_args, $defaults );
 
@@ -57,6 +61,16 @@ public function __invoke( $args, $assoc_args ) {
 			WP_CLI::error( $importer );
 		}
 
+		$importer_class = $assoc_args['importer'];
+		if ( 'WP_Import' !== $importer_class ) {
+			if ( ! class_exists( $importer_class, false ) ) {
+				WP_CLI::error( "Importer class '$importer_class' does not exist." );
+			}
+			if ( ! is_subclass_of( $importer_class, 'WP_Import' ) ) {
+				WP_CLI::error( "Importer class '$importer_class' must be a subclass of WP_Import." );
+			}
+		}
+
 		$this->add_wxr_filters();
 
 		WP_CLI::log( 'Starting the import process...' );
@@ -117,7 +131,9 @@ public function __invoke( $args, $assoc_args ) {
 	 */
 	private function import_wxr( $file, $args ) {
 
-		$wp_import                  = new WP_Import();
+		$importer_class = $args['importer'];
+		/** @var WP_Import $wp_import */
+		$wp_import                  = new $importer_class();
 		$wp_import->processed_posts = $this->processed_posts;
 		$import_data                = $wp_import->parse( $file );