Options, Meta APIs: Prime salts when stored in database.

For salts generated and stored in the database, use `wp_prime_site_option_caches()` within `wp_salt()` to prime the options in a single database query, down from up to nine database queries.

The options are primed when the corresponding constant is either undefined or uses the default string `put your unique phrase here`.

Props joemcgill, spacedmonkey, peterwilsoncc.
Fixes #59871.



git-svn-id: https://develop.svn.wordpress.org/trunk@58837 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/pluggable.php

@@ -2468,6 +2468,41 @@ function wp_salt( $scheme = 'auth' ) {
 			}
 		}
 
+		/*
+		 * Determine which options to prime.
+		 *
+		 * If the salt keys are undefined, use a duplicate value or the
+		 * default `put your unique phrase here` value the salt will be
+		 * generated via `wp_generate_password()` and stored as a site
+		 * option. These options will be primed to avoid repeated
+		 * database requests for undefined salts.
+		 */
+		$options_to_prime = array();
+		foreach ( array( 'auth', 'secure_auth', 'logged_in', 'nonce' ) as $key ) {
+			foreach ( array( 'key', 'salt' ) as $second ) {
+				$const = strtoupper( "{$key}_{$second}" );
+				if ( ! defined( $const ) || true === $duplicated_keys[ constant( $const ) ] ) {
+					$options_to_prime[] = "{$key}_{$second}";
+				}
+			}
+		}
+
+		if ( ! empty( $options_to_prime ) ) {
+			/*
+			 * Also prime `secret_key` used for undefined salting schemes.
+			 *
+			 * If the scheme is unknown the default value for `secret_key` will be
+			 * used to for the salt. This should rarely happen so the option is only
+			 * primed if other salts are undefined.
+			 *
+			 * At this point of execution is is known that a database call will be made
+			 * to prime salts so the `secret_key` option can be primed regardless of the
+			 * constants status.
+			 */
+			$options_to_prime[] = 'secret_key';
+			wp_prime_site_option_caches( $options_to_prime );
+		}
+
 		$values = array(
 			'key'  => '',
 			'salt' => '',