Ticket #28637: 28637.3.diff

src/wp-includes/theme.php

@@ -832 +832 @@
 function get_theme_mod( $name, $default = false ) {
         $mods = get_theme_mods();
 
-        if ( isset( $mods[$name] ) ) {
+        if ( isset( $mods[ $name ] ) && '' !== $mods[ $name ] ) {
                 /**
                  * Filter the theme modification, or 'theme_mod', value.
                  *
@@ -845 +845 @@
                  *
                  * @param string $current_mod The value of the current theme modification.
                  */
-                return apply_filters( "theme_mod_{$name}", $mods[$name] );
+                return apply_filters( "theme_mod_{$name}", $mods[ $name ] );
         }
 
-        if ( is_string( $default ) )
+        if ( is_string( $default ) ) {
                 $default = sprintf( $default, get_template_directory_uri(), get_stylesheet_directory_uri() );
+        }
 
         /** This filter is documented in wp-includes/theme.php */
         return apply_filters( "theme_mod_{$name}", $default );
@@ -881 +882 @@
          */
         $mods[ $name ] = apply_filters( "pre_set_theme_mod_$name", $value, $old_value );
 
+        /*
+         * If the filtered value is an empty string, we should remove it entirely before mods are saved to the database.
+         * This will ensure that any requests for this theme modification name to get_theme_mod() will return false,
+         * and subsequently the default value will be returned if one has been passed to the function.
+         */
+        if ( '' === $mods[ $name ] ) {
+                unset( $mods[ $name ] );
+        }
+
         $theme = get_option( 'stylesheet' );
         update_option( "theme_mods_$theme", $mods );
 }

tests/phpunit/tests/option/themeMods.php

@@ -32 +32 @@
                 $this->assertEquals( '', get_theme_mod( 'test_remove' ) );
         }
 
+        function test_theme_mod_returns_default_when_empty_string_was_previously_saved() {
+                // This is to mimic what would happen when an old mod has already saved an empty string value.
+                $name = 'test_empty_value';
+                $mods = get_theme_mods();
+                $mods[ $name ] = '';
+                $theme = get_option( 'stylesheet' );
+                update_option( "theme_mods_$theme", $mods );
+
+                $this->assertEquals( 'expected', get_theme_mod( 'test_empty_value', 'expected' ) );
+        }
+
+        function test_theme_mod_returns_default_when_empty_string_is_not_saved() {
+                remove_theme_mod( 'test_empty_value' );
+                set_theme_mod( 'test_empty_value', '' );
+                $this->assertEquals( 'expected', get_theme_mod( 'test_empty_value', 'expected' ) );
+        }
+
 }