fix(site-duplication): balance switch_to_blog stack so welcome emails send

inc/duplication/files.php

@@ -23,6 +23,27 @@ class MUCD_Files {
 		 * @param  int $to_site_id   new site id.
 		 */
 		public static function copy_files($from_site_id, $to_site_id) {
+			/*
+			 * Two switch_to_blog() calls are pushed onto the WordPress blog
+			 * stack to read uploads info from the source and destination sites,
+			 * so two restore_current_blog() calls must follow to fully unwind
+			 * the stack. Previously only one restore was issued, leaving the
+			 * caller's blog context pointing at the template/source site after
+			 * copy_files() returned.
+			 *
+			 * The leak broke downstream code that relies on the network/admin
+			 * context — most visibly the site_published email pipeline. When
+			 * a customer signed up with a template the publish flow ran on the
+			 * template's blog context, so wp_mail() picked up the template
+			 * site's options (and per-site SMTP plugins) instead of the
+			 * network's, causing welcome emails to silently fail. Sending a
+			 * test email from the network admin worked because the admin
+			 * request never went through duplication.
+			 *
+			 * @since 2.7.2
+			 * @see https://github.com/Ultimate-Multisite/ultimate-multisite/issues/1163
+			 */
+
 			// Switch to Source site and get uploads info
 			switch_to_blog($from_site_id);
 			$wp_upload_info   = wp_upload_dir();
@@ -34,6 +55,8 @@ public static function copy_files($from_site_id, $to_site_id) {
 			$wp_upload_info = wp_upload_dir();
 			$to_dir         = $wp_upload_info['basedir'];
 
+			// Pop both switches: the destination, then the source.
+			restore_current_blog();
 			restore_current_blog();
 
 			$dirs   = [];

tests/WP_Ultimo/Helpers/Site_Duplicator_Context_Test.php

@@ -0,0 +1,171 @@
+<?php
+/**
+ * Regression tests for site duplication blog-context bookkeeping.
+ *
+ * Covers GH#1163: customers with site templates were not receiving
+ * new-site / welcome emails because MUCD_Files::copy_files() left the
+ * switch_to_blog() stack with the template site on top, so the post-publish
+ * email pipeline ran on the template's blog options and per-site SMTP
+ * plugins instead of the network's.
+ *
+ * @package WP_Ultimo
+ * @subpackage Tests
+ */
+
+namespace WP_Ultimo\Tests\Helpers;
+
+use WP_Ultimo\Helpers\Site_Duplicator;
+use WP_UnitTestCase;
+
+/**
+ * Asserts that the site-duplication code path leaves the WordPress
+ * switch_to_blog() stack balanced and restores the caller's blog context.
+ */
+class Site_Duplicator_Context_Test extends WP_UnitTestCase {
+
+	/**
+	 * Template (source) blog ID.
+	 *
+	 * @var int
+	 */
+	private $template_site_id;
+
+	/**
+	 * Set up: create a template site only. No wu_create_customer() — the
+	 * heavier setUp in Site_Duplicator_Test fails on user-id collisions in
+	 * some local test environments and we don't need a customer here.
+	 */
+	public function setUp(): void {
+		parent::setUp();
+
+		if (! is_multisite()) {
+			$this->markTestSkipped('Site duplication tests require multisite');
+		}
+
+		$this->template_site_id = self::factory()->blog->create(
+			[
+				'domain' => 'context-template.example.com',
+				'path'   => '/',
+				'title'  => 'Context Template',
+			]
+		);
+	}
+
+	/**
+	 * Clean up the template site.
+	 */
+	public function tearDown(): void {
+		if ($this->template_site_id) {
+			wpmu_delete_blog($this->template_site_id, true);
+		}
+
+		parent::tearDown();
+	}
+
+	/**
+	 * MUCD_Files::copy_files() must keep the switch_to_blog() stack balanced —
+	 * exactly one restore_current_blog() per switch_to_blog().
+	 *
+	 * The pre-fix implementation pushed two switch_to_blog() frames (source
+	 * then target) but only popped one, leaking the source site's context
+	 * back to the caller. This test fails on that buggy implementation.
+	 */
+	public function test_copy_files_does_not_leak_blog_context() {
+		$source_id = self::factory()->blog->create(
+			[
+				'domain' => 'copy-files-source.example.com',
+				'path'   => '/',
+				'title'  => 'Copy Files Source',
+			]
+		);
+
+		$target_id = self::factory()->blog->create(
+			[
+				'domain' => 'copy-files-target.example.com',
+				'path'   => '/',
+				'title'  => 'Copy Files Target',
+			]
+		);
+
+		// Defensive: unwind any switch state factory()->blog->create may leak.
+		while (function_exists('ms_is_switched') && ms_is_switched()) {
+			restore_current_blog();
+		}
+
+		$caller_blog_id = get_current_blog_id();
+		$this->assertSame(get_main_site_id(), $caller_blog_id, 'Test prerequisite: caller should be on the main site.');
+
+		// Skip the actual filesystem recursion — we're testing the
+		// switch_to_blog() bookkeeping at the start of copy_files(), not
+		// the file copy itself.
+		add_filter('mucd_copy_dirs', '__return_empty_array', 99);
+
+		\MUCD_Files::copy_files($source_id, $target_id);
+
+		remove_filter('mucd_copy_dirs', '__return_empty_array', 99);
+
+		// Build a diagnostic message in case of failure: shows the residual
+		// switch stack and current blog so it's obvious the unbalanced
+		// switch_to_blog() / restore_current_blog() pairing has regressed.
+		$switched = isset($GLOBALS['_wp_switched_stack']) ? $GLOBALS['_wp_switched_stack'] : [];
+		$msg      = sprintf(
+			'After copy_files(): current=%d, stack=%s, source=%d, target=%d, caller=%d',
+			get_current_blog_id(),
+			wp_json_encode($switched),
+			$source_id,
+			$target_id,
+			$caller_blog_id
+		);
+
+		$this->assertSame(
+			$caller_blog_id,
+			get_current_blog_id(),
+			'copy_files() must restore the caller blog id. ' . $msg
+		);
+
+		$this->assertFalse(
+			ms_is_switched(),
+			'copy_files() must leave the switch_to_blog() stack empty. ' . $msg
+		);
+
+		wpmu_delete_blog($source_id, true);
+		wpmu_delete_blog($target_id, true);
+	}
+
+	/**
+	 * Site_Duplicator::duplicate_site() must restore the caller's blog
+	 * context after the full duplication pipeline runs.
+	 *
+	 * This is the integration-level guard against the email-send regression
+	 * reported in GH#1163.
+	 */
+	public function test_duplicate_site_restores_blog_context() {
+		$caller_blog_id = get_current_blog_id();
+
+		$result = Site_Duplicator::duplicate_site(
+			$this->template_site_id,
+			'Context Restored Site',
+			[
+				'domain' => 'context-restored.example.com',
+				'path'   => '/',
+				'title'  => 'Context Restored Site',
+			]
+		);
+
+		$this->assertIsInt($result, 'duplicate_site() should return the new site id.');
+		$this->assertGreaterThan(0, $result);
+
+		$this->assertSame(
+			$caller_blog_id,
+			get_current_blog_id(),
+			'duplicate_site() must leave the caller on the same blog context it started on.'
+		);
+
+		$this->assertFalse(
+			ms_is_switched(),
+			'duplicate_site() must fully unwind the switch_to_blog() stack.'
+		);
+
+		wpmu_delete_blog($result, true);
+	}
+}