Respect 'default_option_' filters during early sanity checks in `add_option()` and `update_option()`.

`add_option()` and `update_option()` both call `get_option()` to compare the
value passed to the function with any existing value for the given option name.
When a `'default_option_'` filter is in place to change the default value of
an option, `add_option()` and `update_option()` ought to check against the
filtered value, rather than a hardcoded `false`, in order to determine whether
a prior value exists.

Props GregLone, tyxla.
Fixes #31047.
Built from https://develop.svn.wordpress.org/trunk@31473


git-svn-id: http://core.svn.wordpress.org/trunk@31454 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/option.php

@@ -268,7 +268,8 @@ function update_option( $option, $value ) {
 	if ( $value === $old_value )
 		return false;
 
-	if ( false === $old_value )
+	/** This filter is documented in wp-includes/option.php */
+	if ( apply_filters( 'default_option_' . $option, false ) === $old_value )
 		return add_option( $option, $value );
 
 	$serialized_value = maybe_serialize( $value );
@@ -370,7 +371,8 @@ function add_option( $option, $value = '', $deprecated = '', $autoload = 'yes' )
 	// Make sure the option doesn't already exist. We can check the 'notoptions' cache before we ask for a db query
 	$notoptions = wp_cache_get( 'notoptions', 'options' );
 	if ( !is_array( $notoptions ) || !isset( $notoptions[$option] ) )
-		if ( false !== get_option( $option ) )
+		/** This filter is documented in wp-includes/option.php */
+		if ( apply_filters( 'default_option_' . $option, false ) !== get_option( $option ) )
 			return false;
 
 	$serialized_value = maybe_serialize( $value );

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.2-alpha-31472';
+$wp_version = '4.2-alpha-31473';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.