feat: Test Rector to upgrade code for PHP 8.1

rector.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Config\RectorConfig;
+use Rector\Php81\Rector\Array_\FirstClassCallableRector;
+use Rector\TypeDeclaration\Rector\ClassMethod\AddVoidReturnTypeWhereNoReturnRector;
+
+return RectorConfig::configure()
+    ->withPaths([
+        __DIR__ . '/src',
+    ])
+    ->withPhpSets(
+        php81: true,
+    )
+    ->withPreparedSets(
+        deadCode: true,
+        codeQuality: true,
+        earlyReturn: true,
+    )
+    ->withSkip([
+        FirstClassCallableRector::class,
+    ])
+    ->withRules([
+        AddVoidReturnTypeWhereNoReturnRector::class,
+    ]);

src/AccessesPostsLazily.php

@@ -96,7 +96,6 @@ public function getArrayCopy(): array
 
     /**
      * @api
-     * @return array
      */
     public function to_array(): array
     {
@@ -106,7 +105,6 @@ public function to_array(): array
     /**
      * @deprecated 2.0.0 use PostCollectionInterface::to_array() instead
      * @api
-     * @return array
      */
     public function get_posts(): array
     {

src/Archives.php

@@ -94,7 +94,7 @@ public function __construct($args = null, $base = '')
      * @param array|string $args
      * @param string       $base
      */
-    public function init($args = null, $base = '')
+    public function init($args = null, $base = ''): void
     {
         $this->base = $base;
         $this->items = $this->items($args);
@@ -265,29 +265,23 @@ public function items($args = null)
             $limit = \absint($args['limit']);
             $limit = ' LIMIT ' . $limit;
         }
-        $order = \strtoupper($order);
+        $order = \strtoupper((string) $order);
         if ($order !== 'ASC') {
             $order = 'DESC';
         }
 
         // this is what will separate dates on weekly archive links
         $archive_week_separator = '–';
 
-        // over-ride general date format ? 0 = no: use the date format set in Options, 1 = yes: over-ride
-        $archive_date_format_over_ride = 0;
-
         // options for daily archive (only if you over-ride the general date format)
         $archive_day_date_format = 'Y/m/d';
 
         // options for weekly archive (only if you over-ride the general date format)
         $archive_week_start_date_format = 'Y/m/d';
         $archive_week_end_date_format = 'Y/m/d';
-
-        if (!$archive_date_format_over_ride) {
-            $archive_day_date_format = \get_option('date_format');
-            $archive_week_start_date_format = \get_option('date_format');
-            $archive_week_end_date_format = \get_option('date_format');
-        }
+        $archive_day_date_format = \get_option('date_format');
+        $archive_week_start_date_format = \get_option('date_format');
+        $archive_week_end_date_format = \get_option('date_format');
 
         $where = $wpdb->prepare('WHERE post_type = "%s" AND post_status = "publish"', $post_type);
 
@@ -372,7 +366,7 @@ public function items($args = null)
                         $text = $result->ID;
                         if ($result->post_title) {
                             /** This filter is documented in wp-includes/post-template.php */
-                            $text = \strip_tags(\apply_filters('the_title', $result->post_title, $result->ID));
+                            $text = \strip_tags((string) \apply_filters('the_title', $result->post_title, $result->ID));
                         }
                         $output[] = $this->get_archives_link($url, $text);
                     }

src/Attachment.php

@@ -27,7 +27,6 @@ class Attachment extends Post
      * File.
      *
      * @api
-     * @var string
      */
     protected string $file;
 
@@ -65,10 +64,8 @@ class Attachment extends Post
 
     /**
      * Size.
-     *
-     * @var integer|null
      */
-    protected ?int $size;
+    protected ?int $size = null;
 
     /**
      * Gets the src for an attachment.
@@ -132,30 +129,20 @@ public function path(): string
      * Gets the relative path to the uploads folder of an attachment.
      *
      * @api
-     *
-     * @return string
      */
     public function file(): string
     {
-        if (isset($this->file)) {
-            return $this->file;
-        }
-        return $this->file = (string) \get_post_meta($this->ID, '_wp_attached_file', true);
+        return $this->file ?? ($this->file = (string) \get_post_meta($this->ID, '_wp_attached_file', true));
     }
 
     /**
      * Gets the absolute path to an attachment.
      *
      * @api
-     *
-     * @return string
      */
     public function file_loc(): string
     {
-        if (isset($this->file_loc)) {
-            return $this->file_loc;
-        }
-        return $this->file_loc = (string) \get_attached_file($this->ID);
+        return $this->file_loc ?? ($this->file_loc = (string) \get_attached_file($this->ID));
     }
 
     /**
@@ -169,8 +156,6 @@ public function file_loc(): string
      * ```html
      * <a href="http://example.org/wp-content/uploads/2015/08/job-ad-5noe2304i.pdf" download>
      * ```
-     *
-     * @return string
      */
     public function src(): string
     {
@@ -192,8 +177,6 @@ public function src(): string
      *     {% endif %}
      * </figure>
      * ```
-     *
-     * @return string|null
      */
     public function caption(): ?string
     {
@@ -259,7 +242,7 @@ public function size(): ?int
          * @see https://developer.wordpress.org/reference/functions/wp_filesize/
          */
         $size = \filesize($this->file_loc());
-        return $this->size = $size === false ? null : (int) $size;
+        return $this->size = $size === false ? null : $size;
     }
 
     /**
@@ -283,10 +266,7 @@ public function size(): ?int
      */
     public function extension(): string
     {
-        if (isset($this->file_extension)) {
-            return $this->file_extension;
-        }
-        return $this->file_extension = \pathinfo($this->file(), PATHINFO_EXTENSION);
+        return $this->file_extension ?? ($this->file_extension = \pathinfo($this->file(), PATHINFO_EXTENSION));
     }
 
     /**
@@ -345,7 +325,6 @@ public function pathinfo()
      *
      * This method is used to retrieve the attachment metadata only when it's needed.
      *
-     * @param string|null $key
      * @return array|string|int|null
      */
     protected function metadata(?string $key = null)

src/Cache/Cleaner.php

@@ -131,9 +131,7 @@ protected static function delete_transients_multisite()
                         )
                     AND b.meta_value < UNIX_TIMESTAMP()
                 ";
-
-        $clean = $wpdb->query($sql);
-        return $clean;
+        return $wpdb->query($sql);
     }
 
     public static function delete_transients()

src/Cache/KeyGenerator.php

@@ -5,10 +5,9 @@
 class KeyGenerator
 {
     /**
-     * @param mixed $value
      * @return string
      */
-    public function generateKey($value)
+    public function generateKey(mixed $value)
     {
         if (\is_a($value, 'Timber\Cache\TimberKeyGeneratorInterface')) {
             return $value->_get_cache_key();
@@ -20,7 +19,7 @@ public function generateKey($value)
 
         $key = \md5(\json_encode($value));
         if (\is_object($value)) {
-            $key = \get_class($value) . ';' . $key;
+            $key = $value::class . ';' . $key;
         }
 
         // Replace any of the reserved characters.

src/Cache/WPObjectCacheAdapter.php

@@ -6,17 +6,10 @@
 
 class WPObjectCacheAdapter
 {
-    private $cache_group;
-
-    /**
-     * @var Loader
-     */
-    private $timberloader;
-
-    public function __construct(Loader $timberloader, $cache_group = 'timber')
-    {
-        $this->cache_group = $cache_group;
-        $this->timberloader = $timberloader;
+    public function __construct(
+        private readonly Loader $timberloader,
+        private $cache_group = 'timber'
+    ) {
     }
 
     public function fetch($key)