Prevent maintenance mode from changing front page setting

includes/classes/wp-maintenance-mode.php

@@ -126,6 +126,7 @@ private function __construct() {
 					}
 				}
 
+				wpmm_record_show_on_front();
 				update_option( 'show_on_front', 'page' );
 				add_filter(
 					'pre_option_page_on_front',
@@ -162,6 +163,8 @@ function ( $value ) {
 				add_action( 'wpmm_before_scripts', array( $this, 'add_bot_extras' ) );
 				add_action( 'wpmm_footer', array( $this, 'add_js_files' ) );
 			} else {
+				wpmm_restore_show_on_front();
+
 				// restore the maintenance page to its original state when maintenance mode is disabled
 				add_action(
 					'init',
@@ -684,6 +687,8 @@ public static function single_activate( $network_wide = false ) {
 		 * @since 2.0.0
 		 */
 		public static function single_deactivate() {
+			wpmm_restore_show_on_front();
+
 			// give the selected page back to the site in its original state
 			$settings = get_option( 'wpmm_settings' );
 			if ( ! empty( $settings['design']['page_id'] ) ) {

includes/functions/helpers.php

@@ -598,6 +598,32 @@ function wpmm_restore_page_state( $page_id ) {
 	delete_post_meta( $page_id, '_wpmm_applied_status' );
 }
 
+/**
+ * Record the site's front-page setting before maintenance mode changes it.
+ * The first recorded value is kept until maintenance mode is disabled.
+ *
+ * @return void
+ */
+function wpmm_record_show_on_front() {
+	add_option( 'wpmm_original_show_on_front', get_option( 'show_on_front', 'posts' ) );
+}
+
+/**
+ * Restore the front-page setting recorded when maintenance mode was enabled.
+ *
+ * @return void
+ */
+function wpmm_restore_show_on_front() {
+	$original_value = get_option( 'wpmm_original_show_on_front', false );
+
+	if ( false === $original_value ) {
+		return;
+	}
+
+	update_option( 'show_on_front', $original_value );
+	delete_option( 'wpmm_original_show_on_front' );
+}
+
 /**
  * Switch the selected maintenance page: hand the previous page back and take
  * the new one over. The caller is responsible for saving the new selection.

tests/page-state-test.php

@@ -736,13 +736,43 @@ public function test_plugin_deactivation_restores_selected_page() {
 			)
 		);
 
+		update_option( 'show_on_front', 'posts' );
+
 		// Maintenance mode is active: the page is taken over and published.
 		$this->boot_plugin( $this->make_settings( 1, $page_id ) );
 		$this->assertSame( 'publish', get_post_status( $page_id ) );
+		$this->assertSame( 'page', get_option( 'show_on_front' ) );
+		$this->assertSame( 'posts', get_option( 'wpmm_original_show_on_front' ) );
 
-		// Deactivating the plugin hands the page back, private again.
+		// Deactivating the plugin hands both the page and Reading setting back.
 		WP_Maintenance_Mode::single_deactivate();
 
 		$this->assertSame( 'private', get_post_status( $page_id ) );
+		$this->assertSame( 'posts', get_option( 'show_on_front' ) );
+		$this->assertFalse( get_option( 'wpmm_original_show_on_front', false ) );
+	}
+
+	public function test_disabling_maintenance_mode_restores_the_initial_reading_setting() {
+		$page_id = self::factory()->post->create(
+			array(
+				'post_type'   => 'page',
+				'post_status' => 'publish',
+			)
+		);
+
+		update_option( 'show_on_front', 'posts' );
+		$this->boot_plugin( $this->make_settings( 1, $page_id ) );
+		$this->assertSame( 'page', get_option( 'show_on_front' ) );
+		$this->assertSame( 'posts', get_option( 'wpmm_original_show_on_front' ) );
+
+		// Another active request must not overwrite the recorded initial value.
+		$this->boot_plugin( $this->make_settings( 1, $page_id ) );
+		$this->assertSame( 'posts', get_option( 'wpmm_original_show_on_front' ) );
+
+		$this->boot_plugin( $this->make_settings( 0, $page_id ) );
+		do_action( 'init' );
+
+		$this->assertSame( 'posts', get_option( 'show_on_front' ) );
+		$this->assertFalse( get_option( 'wpmm_original_show_on_front', false ) );
 	}
 }

uninstall.php

@@ -17,6 +17,7 @@ function single_uninstall() {
 		'wpmm_settings',
 		'wpmm_notice',
 		'wpmm_version',
+		'wpmm_original_show_on_front',
 	);
 
 	foreach ( $options_to_delete as $option ) {