[wp-trac] [WordPress Trac] #58317: Refactor determine_locale() for performance

[WordPress Trac]

#58317: Refactor determine_locale() for performance
-------------------------+-----------------------------
 Reporter:  Cybr         |      Owner:  (none)
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:  Awaiting Review
Component:  General      |    Version:  trunk
 Severity:  minor        |   Keywords:  has-patch
  Focuses:  performance  |
-------------------------+-----------------------------
 `determine_locale()` breaks various performance tropes. Albeit an obscure
 function, I hope this refactor will be the first of many.

 The first defense clause:
 {{{#!php
 <?PHP
 if ( ! empty( $determined_locale ) && is_string( $determined_locale ) ) {
 }}}
 Could become:
 {{{#!php
 <?PHP
 if ( $determined_locale && is_string( $determined_locale ) ) {
 }}}
 Here, I removed a function call and a NOT operation, resulting in exactly
 the same code.

 Determining the user locale:
 {{{#!php
 <?php
 $determined_locale = get_locale();

 if ( is_admin() ) {
         $determined_locale = get_user_locale();
 }

 if ( isset( $_GET['_locale'] ) && 'user' === $_GET['_locale'] &&
 wp_is_json_request() ) {
         $determined_locale = get_user_locale();
 }
 }}}
 Could become:
 {{{#!php
 <?php
 if (
            is_admin()
         || ( isset( $_GET['_locale'] ) && 'user' === $_GET['_locale'] &&
 wp_is_json_request() )
 ) {
         $determined_locale = get_user_locale();
 } else {
         $determined_locale = get_locale();
 }
 }}}
 Here I exchange a jump for an operator (first and second if-statements are
 combined and exchanged with a logic operator). I also removed writing to
 the variable twice in admin and insecure JSON requests.

 Writing WP lang:
 {{{#!php
 <?php
 $wp_lang = '';

 if ( ! empty( $_GET['wp_lang'] ) ) {
         $wp_lang = sanitize_text_field( $_GET['wp_lang'] );
 } elseif ( ! empty( $_COOKIE['wp_lang'] ) ) {
         $wp_lang = sanitize_text_field( $_COOKIE['wp_lang'] );
 }

 if ( ! empty( $wp_lang ) && ! empty( $GLOBALS['pagenow'] ) && 'wp-
 login.php' === $GLOBALS['pagenow'] ) {
         $determined_locale = $wp_lang;
 }
 }}}
 Could become:
 {{{#!php
 <?php
 if ( isset( $GLOBALS['pagenow'] ) && 'wp-login.php' ===
 $GLOBALS['pagenow'] ) {
         if ( ! empty( $_GET['wp_lang'] ) ) {
                 $determined_locale = sanitize_text_field( $_GET['wp_lang']
 ) ?: $determined_locale;
         } elseif ( ! empty( $_COOKIE['wp_lang'] ) ) {
                 $determined_locale = sanitize_text_field(
 $_COOKIE['wp_lang'] ) ?: $determined_locale;
         }
 }
 }}}
 Here, instead of writing to `$wp_lang` twice, and then determining whether
 we actually should use that value if the second attempt didn't happen, we
 first determine the latter. Using the amazing power of the short ternary,
 we spare a jump if the value amounts to nothing.

 Still, the last two refactorizations could be combined, but I could not
 think of a way to maintain readability while keeping in mind "DRY"
 standards.

 The refactorization makes the function about [https://3v4l.org/9PsqQ 1.5x
 faster on the front-end], and about [https://3v4l.org/NNkoU 2.2x faster in
 admin] — without changing any functionality.

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/58317>
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