Ticket #38168: 38168.diff

src/wp-includes/post-template.php

@@ -711 +711 @@
                 $classes[] = 'no-customize-support';
         }
 
-        if ( get_background_color() !== get_theme_support( 'custom-background', 'default-color' ) || get_background_image() )
+        if ( current_theme_supports( 'custom-background' ) &&
+             (
+                     get_background_color() !== get_theme_support( 'custom-background', 'default-color' )
+                     || get_background_image()
+             )
+        ) {
                 $classes[] = 'custom-background';
+        }
 
         if ( has_custom_logo() ) {
                 $classes[] = 'wp-custom-logo';

tests/phpunit/tests/post/getBodyClass.php

@@ -92 +92 @@
                 $this->assertContains( "single-format-standard", $class );
         }
 
+        /**
+         * @ticket 38168
+         */
+        public function test_custom_background_class_is_added_when_theme_supports_it() {
+                set_theme_mod( 'background_color', '#000000' );
+
+                $actual = get_body_class();
+
+                set_theme_mod( 'background_color', false );
+
+                $this->assertTrue( current_theme_supports( 'custom-background' ) );
+                $this->assertContains( 'custom-background', $actual );
+        }
+
+        /**
+         * @ticket 38168
+         */
+        public function test_custom_background_class_is_not_added_when_theme_support_is_missing() {
+                set_theme_mod( 'background_color', '#000000' );
+
+                $theme_support = get_theme_support( 'custom-background' );
+                remove_theme_support( 'custom-background' );
+
+                $actual = get_body_class();
+
+                add_theme_support( 'custom-background', $theme_support );
+                set_theme_mod( 'background_color', false );
+
+                $this->assertNotContains( 'custom-background', $actual );
+        }
 }