From 75719607d872eb8c4069dccd92bc47bc518b186d Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Mon, 25 Apr 2022 12:49:37 +0200
Subject: [PATCH 01/21] Fix a bug in the
 WP_REST_Pattern_Directory_Controller:get_items. We must also implode slugs as
 implode doesn't work with multi-dimensional arrays.

---
 ...s-wp-rest-pattern-directory-controller.php |  47 ++++++--
 .../rest-pattern-directory-controller.php     | 110 ++++++++++++++++++
 2 files changed, 147 insertions(+), 10 deletions(-)

diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
index 28f42fd5a4938..a8b53081b79b8 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
@@ -119,16 +119,7 @@ public function get_items( $request ) {
 			$query_args['slug'] = $slug;
 		}
 
-		/*
-		 * Include a hash of the query args, so that different requests are stored in
-		 * separate caches.
-		 *
-		 * MD5 is chosen for its speed, low-collision rate, universal availability, and to stay
-		 * under the character limit for `_site_transient_timeout_{...}` keys.
-		 *
-		 * @link https://stackoverflow.com/questions/3665247/fastest-hash-for-non-cryptographic-uses
-		 */
-		$transient_key = 'wp_remote_block_patterns_' . md5( implode( '-', $query_args ) );
+		$transient_key = $this->get_transient_key( $query_args );
 
 		/*
 		 * Use network-wide transient to improve performance. The locale is the only site
@@ -346,4 +337,40 @@ public function get_collection_params() {
 		 */
 		return apply_filters( 'rest_pattern_directory_collection_params', $query_params );
 	}
+
+	/*
+	 * Include a hash of the query args, so that different requests are stored in
+	 * separate caches.
+	 *
+	 * MD5 is chosen for its speed, low-collision rate, universal availability, and to stay
+	 * under the character limit for `_site_transient_timeout_{...}` keys.
+	 *
+	 * @link https://stackoverflow.com/questions/3665247/fastest-hash-for-non-cryptographic-uses
+	 *
+	 * @since 6.0.0
+	 *
+	 * @param array $query_args Query arguments to generate a transient key from.
+	 *
+	 * @return string Transient key.
+	 */
+	private function get_transient_key( $query_args ) {
+
+		if ( array_key_exists( 'slug', $query_args ) ) {
+			if ( ! is_array( $query_args['slug'] ) ) {
+				$query_args['slug'] = explode( ',', (string) $query_args['slug'] );
+			}
+
+			// Let's sort the array so the transient key doesn't depend on the order of slugs.
+			sort( $query_args['slug'] );
+
+			// Slugs have to be imploded separately as implode doesn't work with recursive arrays.
+			$query_args['slug'] = implode( ',', $query_args['slug'] );
+
+			if ( '' === trim( $query_args['slug'] ) ) {
+				unset( $query_args['slug'] );
+			}
+		}
+
+		return 'wp_remote_block_patterns_' . md5( implode( '-', $query_args ) );
+	}
 }
diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index 53a2e0b3646b9..bb454da5682de 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -21,6 +21,15 @@ class WP_REST_Pattern_Directory_Controller_Test extends WP_Test_REST_Controller_
 	 */
 	protected static $contributor_id;
 
+	/**
+	 * An instance of WP_REST_Pattern_Directory_Controller class.
+	 *
+	 * @since 6.0.0
+	 *
+	 * @var WP_REST_Pattern_Directory_Controller
+	 */
+	private static $controller;
+
 	/**
 	 * Set up class test fixtures.
 	 *
@@ -34,6 +43,8 @@ public static function wpSetUpBeforeClass( $factory ) {
 				'role' => 'contributor',
 			)
 		);
+
+		static::$controller = new WP_REST_Pattern_Directory_Controller();
 	}
 
 	/**
@@ -399,6 +410,88 @@ public function test_get_item_schema() {
 		$this->markTestSkipped( "The controller's schema is hardcoded, so tests would not be meaningful." );
 	}
 
+	/**
+	 * Tests if the transient key gets generated correctly.
+	 *
+	 * @dataProvider data_get_query_parameters
+	 *
+	 * @covers WP_REST_Pattern_Directory_Controller::get_transient_key
+	 *
+	 * @ticket xxxxx
+	 *
+	 * @param array     $parameters_1   Expected query arguments.
+	 * @param array     $parameters_2   Actual query arguments.
+	 * @param string    $message        An error message to display.
+	 * @param bool      $assert_same    Assertion type (assertSame vs assertNotSame).
+	 */
+	public function test_transient_keys_get_generated_correctly( $parameters_1, $parameters_2, $message, $assert_same = true ) {
+		$method = $this->get_reflection_method( self::$controller, 'get_transient_key' );
+
+		$result_1 = $method->invoke( self::$controller, $parameters_1 );
+		$result_2 = $method->invoke( self::$controller, $parameters_2 );
+
+		$this->assertIsString( $result_1 );
+		$this->assertNotEmpty( $result_1 );
+
+		$this->assertIsString( $result_2 );
+		$this->assertNotEmpty( $result_2 );
+
+		if ( $assert_same ) {
+			$this->assertSame( $result_1, $result_2, $message );
+		} else {
+			$this->assertNotSame( $result_1, $result_2, $message );
+		}
+
+	}
+
+	public function data_get_query_parameters() {
+		return array(
+			array(
+				array(
+					'parameter_1' => 1,
+					'slug'        => null,
+				),
+				array(
+					'parameter_1' => 1,
+				),
+				'Empty slugs should not affect the transient key.'
+			),
+			array(
+				array(
+					'parameter_1' => 1,
+					'slug'        => false,
+				),
+				array(
+					'parameter_1' => 1,
+				),
+				'Empty slugs should not affect the transient key.'
+			),
+			array(
+				array(
+					'parameter_1' => 1,
+					'slug'        => '1,2',
+				),
+				array(
+					'parameter_1' => 1,
+					'slug'        => '2,1',
+				),
+				'message' => 'The order of slugs should not affect transient key.'
+			),
+			array(
+				array(
+					'parameter_1' => 1,
+					'slug'        => 'some_slug',
+				),
+				array(
+					'parameter_1' => 1,
+					'slug'        => 'some_other_slug',
+				),
+				'message' => 'Transient keys must not match.',
+				false,
+			),
+		);
+	}
+
 	/**
 	 * Simulate a successful outbound HTTP requests, to keep tests pure and performant.
 	 *
@@ -461,4 +554,21 @@ static function ( $return, $args, $url ) use ( $blocked_host ) {
 			3
 		);
 	}
+
+	/**
+	 * Returns a reflection method and changes its scope.
+	 *
+	 * @since 6.0.0
+	 *
+	 * @param $object An object that has a private method that has to be called.
+	 * @param $method Name of the method.
+	 *
+	 * @return ReflectionMethod
+	 */
+	private function get_reflection_method($object, $method)
+	{
+		$reflection_method = new ReflectionMethod($object, $method);
+		$reflection_method->setAccessible(true);
+		return $reflection_method;
+	}
 }

From f06d3d0768c473c0cb020f278f1e776bbfec1f82 Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Mon, 25 Apr 2022 18:06:46 +0200
Subject: [PATCH 02/21] Update ticket reference.

---
 .../tests/rest-api/rest-pattern-directory-controller.php        | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index bb454da5682de..928b7e49a9514 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -417,7 +417,7 @@ public function test_get_item_schema() {
 	 *
 	 * @covers WP_REST_Pattern_Directory_Controller::get_transient_key
 	 *
-	 * @ticket xxxxx
+	 * @ticket 55617
 	 *
 	 * @param array     $parameters_1   Expected query arguments.
 	 * @param array     $parameters_2   Actual query arguments.

From b504030a99e8856b7fef20fea247f57210198bee Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Mon, 25 Apr 2022 18:22:00 +0200
Subject: [PATCH 03/21] Fix code style.

---
 .../rest-pattern-directory-controller.php      | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index 928b7e49a9514..e7e586d652389 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -454,7 +454,7 @@ public function data_get_query_parameters() {
 				array(
 					'parameter_1' => 1,
 				),
-				'Empty slugs should not affect the transient key.'
+				'Empty slugs should not affect the transient key.',
 			),
 			array(
 				array(
@@ -464,7 +464,7 @@ public function data_get_query_parameters() {
 				array(
 					'parameter_1' => 1,
 				),
-				'Empty slugs should not affect the transient key.'
+				'Empty slugs should not affect the transient key.',
 			),
 			array(
 				array(
@@ -475,7 +475,7 @@ public function data_get_query_parameters() {
 					'parameter_1' => 1,
 					'slug'        => '2,1',
 				),
-				'message' => 'The order of slugs should not affect transient key.'
+				'message' => 'The order of slugs should not affect transient key.',
 			),
 			array(
 				array(
@@ -558,17 +558,17 @@ static function ( $return, $args, $url ) use ( $blocked_host ) {
 	/**
 	 * Returns a reflection method and changes its scope.
 	 *
-	 * @since 6.0.0
-	 *
 	 * @param $object An object that has a private method that has to be called.
 	 * @param $method Name of the method.
 	 *
 	 * @return ReflectionMethod
+	 * @since 6.0.0
+	 *
 	 */
-	private function get_reflection_method($object, $method)
-	{
-		$reflection_method = new ReflectionMethod($object, $method);
-		$reflection_method->setAccessible(true);
+	private function get_reflection_method( $object, $method ) {
+		$reflection_method = new ReflectionMethod( $object, $method );
+		$reflection_method->setAccessible( true );
+
 		return $reflection_method;
 	}
 }

From b1598ab4191ac31cb8f3e019163f7c384a22ad5a Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Mon, 25 Apr 2022 18:42:18 +0200
Subject: [PATCH 04/21] Add `slug` to the collection parameters. Previously, it
 was missing.

---
 .../endpoints/class-wp-rest-pattern-directory-controller.php | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
index a8b53081b79b8..8c3c822cccd45 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
@@ -328,6 +328,11 @@ public function get_collection_params() {
 			'minimum'     => 1,
 		);
 
+		$query_params['slug'] = array(
+			'description' => __( 'Limit results to those matching a pattern (slug).' ),
+			'type'        => array( 'string', 'array' ),
+		);
+
 		/**
 		 * Filter collection parameters for the block pattern directory controller.
 		 *

From e284e1ec8bccca44cce52eda596c04925320407c Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Mon, 25 Apr 2022 18:57:58 +0200
Subject: [PATCH 05/21] Improve PHPDOC blocks.

---
 .../rest-api/rest-pattern-directory-controller.php    | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index e7e586d652389..30bfd7a9ea058 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -417,6 +417,8 @@ public function test_get_item_schema() {
 	 *
 	 * @covers WP_REST_Pattern_Directory_Controller::get_transient_key
 	 *
+	 * @since 6.0.0
+	 *
 	 * @ticket 55617
 	 *
 	 * @param array     $parameters_1   Expected query arguments.
@@ -444,6 +446,11 @@ public function test_transient_keys_get_generated_correctly( $parameters_1, $par
 
 	}
 
+	/**
+	 * @since 6.0.0
+	 *
+	 * @ticket 55617
+	 */
 	public function data_get_query_parameters() {
 		return array(
 			array(
@@ -558,12 +565,12 @@ static function ( $return, $args, $url ) use ( $blocked_host ) {
 	/**
 	 * Returns a reflection method and changes its scope.
 	 *
+	 * @since 6.0.0
+	 *
 	 * @param $object An object that has a private method that has to be called.
 	 * @param $method Name of the method.
 	 *
 	 * @return ReflectionMethod
-	 * @since 6.0.0
-	 *
 	 */
 	private function get_reflection_method( $object, $method ) {
 		$reflection_method = new ReflectionMethod( $object, $method );

From 7fb829d45cf98a0d4184fb14371bc84f4c91a580 Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Mon, 25 Apr 2022 20:23:08 +0200
Subject: [PATCH 06/21] Update wp-api-generated.js schema.

---
 tests/qunit/fixtures/wp-api-generated.js | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tests/qunit/fixtures/wp-api-generated.js b/tests/qunit/fixtures/wp-api-generated.js
index c8874649d707d..84dfaf24141e6 100644
--- a/tests/qunit/fixtures/wp-api-generated.js
+++ b/tests/qunit/fixtures/wp-api-generated.js
@@ -10385,7 +10385,15 @@ mockedApiResponse.Schema = {
                             "type": "integer",
                             "minimum": 1,
                             "required": false
-                        }
+						},
+						"slug": {
+							"description": "Limit results to those matching a pattern (slug).",
+							"type": [
+								"string",
+								"array"
+							],
+							required: false
+						}
                     }
                 }
             ],

From 07aa848c3c96c54a6962f9269a6d79efb4869ffd Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Mon, 25 Apr 2022 20:37:37 +0200
Subject: [PATCH 07/21] Update wp-api-generated.js schema.

---
 tests/qunit/fixtures/wp-api-generated.js | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/tests/qunit/fixtures/wp-api-generated.js b/tests/qunit/fixtures/wp-api-generated.js
index 84dfaf24141e6..f94be665d5d98 100644
--- a/tests/qunit/fixtures/wp-api-generated.js
+++ b/tests/qunit/fixtures/wp-api-generated.js
@@ -10385,15 +10385,15 @@ mockedApiResponse.Schema = {
                             "type": "integer",
                             "minimum": 1,
                             "required": false
-						},
-						"slug": {
-							"description": "Limit results to those matching a pattern (slug).",
-							"type": [
-								"string",
-								"array"
-							],
-							required: false
-						}
+                        },
+                        "slug": {
+                            "description": "Limit results to those matching a pattern (slug).",
+                            "type": [
+                                "string",
+                                "array"
+                            ],
+                            required: false
+                        }
                     }
                 }
             ],

From fd1642d736e10ef023bce233b5acc8b4be3af78a Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Mon, 25 Apr 2022 20:47:12 +0200
Subject: [PATCH 08/21] Update wp-api-generated.js schema.

---
 tests/qunit/fixtures/wp-api-generated.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/qunit/fixtures/wp-api-generated.js b/tests/qunit/fixtures/wp-api-generated.js
index f94be665d5d98..0abee9959e91a 100644
--- a/tests/qunit/fixtures/wp-api-generated.js
+++ b/tests/qunit/fixtures/wp-api-generated.js
@@ -10392,7 +10392,7 @@ mockedApiResponse.Schema = {
                                 "string",
                                 "array"
                             ],
-                            required: false
+                            "required": false
                         }
                     }
                 }

From 5c9a336481cb584064cb5a9ed7105b1f33316236 Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Mon, 25 Apr 2022 22:09:54 +0200
Subject: [PATCH 09/21] Update comment.

---
 .../endpoints/class-wp-rest-pattern-directory-controller.php    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
index 8c3c822cccd45..20d491df72eb7 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
@@ -365,7 +365,7 @@ private function get_transient_key( $query_args ) {
 				$query_args['slug'] = explode( ',', (string) $query_args['slug'] );
 			}
 
-			// Let's sort the array so the transient key doesn't depend on the order of slugs.
+			// Sort the array so that the transient key doesn't depend on the order of slugs.
 			sort( $query_args['slug'] );
 
 			// Slugs have to be imploded separately as implode doesn't work with recursive arrays.

From 5e923bc73da1322a2b64bfaf9fc090abfadfc57b Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Tue, 26 Apr 2022 11:17:42 +0200
Subject: [PATCH 10/21] "Slug" must be of type array. Strings will be
 automatically converted to an array. Per suggestion here:
 https://github.com/WordPress/wordpress-develop/pull/2625#discussion_r858069357

---
 .../endpoints/class-wp-rest-pattern-directory-controller.php | 2 +-
 tests/qunit/fixtures/wp-api-generated.js                     | 5 +----
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
index 20d491df72eb7..786abb628786e 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
@@ -330,7 +330,7 @@ public function get_collection_params() {
 
 		$query_params['slug'] = array(
 			'description' => __( 'Limit results to those matching a pattern (slug).' ),
-			'type'        => array( 'string', 'array' ),
+			'type'        => 'array',
 		);
 
 		/**
diff --git a/tests/qunit/fixtures/wp-api-generated.js b/tests/qunit/fixtures/wp-api-generated.js
index 0abee9959e91a..6161cf14fc137 100644
--- a/tests/qunit/fixtures/wp-api-generated.js
+++ b/tests/qunit/fixtures/wp-api-generated.js
@@ -10388,10 +10388,7 @@ mockedApiResponse.Schema = {
                         },
                         "slug": {
                             "description": "Limit results to those matching a pattern (slug).",
-                            "type": [
-                                "string",
-                                "array"
-                            ],
+                            "type": "array",
                             "required": false
                         }
                     }

From c2122fb148d7257f6cbf254a94de6711871fac60 Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Tue, 26 Apr 2022 18:22:42 +0200
Subject: [PATCH 11/21] Change the scope of the
 WP_REST_Pattern_Directory_Controller::get_transient_key method as it would be
 helpful to make it available to child classes.

---
 .../endpoints/class-wp-rest-pattern-directory-controller.php    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
index 786abb628786e..a4b24b0505cb6 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
@@ -358,7 +358,7 @@ public function get_collection_params() {
 	 *
 	 * @return string Transient key.
 	 */
-	private function get_transient_key( $query_args ) {
+	protected function get_transient_key( $query_args ) {
 
 		if ( array_key_exists( 'slug', $query_args ) ) {
 			if ( ! is_array( $query_args['slug'] ) ) {

From 005de4aa8ae617dc0df455d433861e7a83bf4bce Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Wed, 27 Apr 2022 01:09:40 +0200
Subject: [PATCH 12/21] Replace array_key_exist with isset because
 $query_args['slug'] isn't supposed to be null.

---
 ...s-wp-rest-pattern-directory-controller.php |  7 +++----
 .../rest-pattern-directory-controller.php     | 20 +++++--------------
 2 files changed, 8 insertions(+), 19 deletions(-)

diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
index a4b24b0505cb6..a6848f301d214 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
@@ -360,10 +360,9 @@ public function get_collection_params() {
 	 */
 	protected function get_transient_key( $query_args ) {
 
-		if ( array_key_exists( 'slug', $query_args ) ) {
-			if ( ! is_array( $query_args['slug'] ) ) {
-				$query_args['slug'] = explode( ',', (string) $query_args['slug'] );
-			}
+		if ( isset( $query_args['slug'] ) ) {
+			// This is an additional precaution because the "sort" function expects an array.
+			$query_args['slug'] = (array) $query_args['slug'];
 
 			// Sort the array so that the transient key doesn't depend on the order of slugs.
 			sort( $query_args['slug'] );
diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index 30bfd7a9ea058..4fa25dd665c05 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -456,7 +456,7 @@ public function data_get_query_parameters() {
 			array(
 				array(
 					'parameter_1' => 1,
-					'slug'        => null,
+					'slug'        => array(),
 				),
 				array(
 					'parameter_1' => 1,
@@ -466,32 +466,22 @@ public function data_get_query_parameters() {
 			array(
 				array(
 					'parameter_1' => 1,
-					'slug'        => false,
+					'slug'        => array( 0, 2 ),
 				),
 				array(
 					'parameter_1' => 1,
-				),
-				'Empty slugs should not affect the transient key.',
-			),
-			array(
-				array(
-					'parameter_1' => 1,
-					'slug'        => '1,2',
-				),
-				array(
-					'parameter_1' => 1,
-					'slug'        => '2,1',
+					'slug'        => array( 2, 0 ),
 				),
 				'message' => 'The order of slugs should not affect transient key.',
 			),
 			array(
 				array(
 					'parameter_1' => 1,
-					'slug'        => 'some_slug',
+					'slug'        => array( 'some_slug' ),
 				),
 				array(
 					'parameter_1' => 1,
-					'slug'        => 'some_other_slug',
+					'slug'        => array( 'some_other_slug' ),
 				),
 				'message' => 'Transient keys must not match.',
 				false,

From 0a2c2ebfbfaf9de86be352e0957942f73b253f81 Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Wed, 27 Apr 2022 16:15:42 +0200
Subject: [PATCH 13/21] Pass $query_args['slugs'] through wp_parse_list to
 ensure that it is an array.

---
 .../endpoints/class-wp-rest-pattern-directory-controller.php    | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
index a6848f301d214..4e11ef78bd6b5 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
@@ -362,7 +362,7 @@ protected function get_transient_key( $query_args ) {
 
 		if ( isset( $query_args['slug'] ) ) {
 			// This is an additional precaution because the "sort" function expects an array.
-			$query_args['slug'] = (array) $query_args['slug'];
+			$query_args['slug'] = wp_parse_list( $query_args['slug'] );
 
 			// Sort the array so that the transient key doesn't depend on the order of slugs.
 			sort( $query_args['slug'] );

From 7d1c51221c42336c151aa454c7ce3b407b7e250f Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Wed, 27 Apr 2022 16:58:21 +0200
Subject: [PATCH 14/21] Refactor WP_REST_Pattern_Directory_Controller_Test. Use
 WP_REST_Pattern_Directory_Controller_Test::setUp to set up the controller.

---
 .../rest-pattern-directory-controller.php     | 47 ++++++++-----------
 1 file changed, 19 insertions(+), 28 deletions(-)

diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index 4fa25dd665c05..25fa0cd796b9e 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -28,7 +28,7 @@ class WP_REST_Pattern_Directory_Controller_Test extends WP_Test_REST_Controller_
 	 *
 	 * @var WP_REST_Pattern_Directory_Controller
 	 */
-	private static $controller;
+	private $controller;
 
 	/**
 	 * Set up class test fixtures.
@@ -43,8 +43,17 @@ public static function wpSetUpBeforeClass( $factory ) {
 				'role' => 'contributor',
 			)
 		);
+	}
 
-		static::$controller = new WP_REST_Pattern_Directory_Controller();
+	/**
+	 * Set up class test fixtures.
+	 *
+	 * @since 6.0.0
+	 */
+	public function setUp() {
+		parent::setUp();
+
+		$this->controller = new WP_REST_Pattern_Directory_Controller();
 	}
 
 	/**
@@ -333,12 +342,11 @@ public function test_delete_item() {
 	 * @since 5.8.0
 	 */
 	public function test_prepare_item() {
-		$controller                   = new WP_REST_Pattern_Directory_Controller();
 		$raw_patterns                 = json_decode( self::get_raw_response( 'browse-all' ) );
 		$raw_patterns[0]->extra_field = 'this should be removed';
 
-		$prepared_pattern = $controller->prepare_response_for_collection(
-			$controller->prepare_item_for_response( $raw_patterns[0], new WP_REST_Request() )
+		$prepared_pattern = $this->controller->prepare_response_for_collection(
+			$this->controller->prepare_item_for_response( $raw_patterns[0], new WP_REST_Request() )
 		);
 
 		$this->assertPatternMatchesSchema( $prepared_pattern );
@@ -351,12 +359,11 @@ public function test_prepare_item() {
 	 * @since 5.8.0
 	 */
 	public function test_prepare_item_search() {
-		$controller                   = new WP_REST_Pattern_Directory_Controller();
 		$raw_patterns                 = json_decode( self::get_raw_response( 'search' ) );
 		$raw_patterns[0]->extra_field = 'this should be removed';
 
-		$prepared_pattern = $controller->prepare_response_for_collection(
-			$controller->prepare_item_for_response( $raw_patterns[0], new WP_REST_Request() )
+		$prepared_pattern = $this->controller->prepare_response_for_collection(
+			$this->controller->prepare_item_for_response( $raw_patterns[0], new WP_REST_Request() )
 		);
 
 		$this->assertPatternMatchesSchema( $prepared_pattern );
@@ -427,10 +434,11 @@ public function test_get_item_schema() {
 	 * @param bool      $assert_same    Assertion type (assertSame vs assertNotSame).
 	 */
 	public function test_transient_keys_get_generated_correctly( $parameters_1, $parameters_2, $message, $assert_same = true ) {
-		$method = $this->get_reflection_method( self::$controller, 'get_transient_key' );
+		$reflection_method = new ReflectionMethod( $this->controller, 'get_transient_key' );
+		$reflection_method->setAccessible( true );
 
-		$result_1 = $method->invoke( self::$controller, $parameters_1 );
-		$result_2 = $method->invoke( self::$controller, $parameters_2 );
+		$result_1 = $reflection_method->invoke( self::$controller, $parameters_1 );
+		$result_2 = $reflection_method->invoke( self::$controller, $parameters_2 );
 
 		$this->assertIsString( $result_1 );
 		$this->assertNotEmpty( $result_1 );
@@ -551,21 +559,4 @@ static function ( $return, $args, $url ) use ( $blocked_host ) {
 			3
 		);
 	}
-
-	/**
-	 * Returns a reflection method and changes its scope.
-	 *
-	 * @since 6.0.0
-	 *
-	 * @param $object An object that has a private method that has to be called.
-	 * @param $method Name of the method.
-	 *
-	 * @return ReflectionMethod
-	 */
-	private function get_reflection_method( $object, $method ) {
-		$reflection_method = new ReflectionMethod( $object, $method );
-		$reflection_method->setAccessible( true );
-
-		return $reflection_method;
-	}
 }

From 1257482d039b0322f78f0781c732deb80b0e9c67 Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Wed, 27 Apr 2022 19:36:51 +0200
Subject: [PATCH 15/21] Refactor the test to use the static $controller
 property. It seems there is some issue with the ::setUp method.

---
 .../rest-pattern-directory-controller.php     | 25 ++++++-------------
 1 file changed, 8 insertions(+), 17 deletions(-)

diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index 25fa0cd796b9e..807037da86484 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -28,7 +28,7 @@ class WP_REST_Pattern_Directory_Controller_Test extends WP_Test_REST_Controller_
 	 *
 	 * @var WP_REST_Pattern_Directory_Controller
 	 */
-	private $controller;
+	private static $controller;
 
 	/**
 	 * Set up class test fixtures.
@@ -43,17 +43,8 @@ public static function wpSetUpBeforeClass( $factory ) {
 				'role' => 'contributor',
 			)
 		);
-	}
-
-	/**
-	 * Set up class test fixtures.
-	 *
-	 * @since 6.0.0
-	 */
-	public function setUp() {
-		parent::setUp();
 
-		$this->controller = new WP_REST_Pattern_Directory_Controller();
+		static::$controller = new WP_REST_Pattern_Directory_Controller();
 	}
 
 	/**
@@ -62,7 +53,7 @@ public function setUp() {
 	 * @param WP_REST_Response[] $pattern An individual pattern from the REST API response.
 	 */
 	public function assertPatternMatchesSchema( $pattern ) {
-		$schema     = ( new WP_REST_Pattern_Directory_Controller() )->get_item_schema();
+		$schema     = static::$controller->get_item_schema();
 		$pattern_id = isset( $pattern->id ) ? $pattern->id : '{pattern ID is missing}';
 
 		$this->assertTrue(
@@ -345,8 +336,8 @@ public function test_prepare_item() {
 		$raw_patterns                 = json_decode( self::get_raw_response( 'browse-all' ) );
 		$raw_patterns[0]->extra_field = 'this should be removed';
 
-		$prepared_pattern = $this->controller->prepare_response_for_collection(
-			$this->controller->prepare_item_for_response( $raw_patterns[0], new WP_REST_Request() )
+		$prepared_pattern = static::$controller->prepare_response_for_collection(
+			static::$controller->prepare_item_for_response( $raw_patterns[0], new WP_REST_Request() )
 		);
 
 		$this->assertPatternMatchesSchema( $prepared_pattern );
@@ -362,8 +353,8 @@ public function test_prepare_item_search() {
 		$raw_patterns                 = json_decode( self::get_raw_response( 'search' ) );
 		$raw_patterns[0]->extra_field = 'this should be removed';
 
-		$prepared_pattern = $this->controller->prepare_response_for_collection(
-			$this->controller->prepare_item_for_response( $raw_patterns[0], new WP_REST_Request() )
+		$prepared_pattern = static::$controller->prepare_response_for_collection(
+			static::$controller->prepare_item_for_response( $raw_patterns[0], new WP_REST_Request() )
 		);
 
 		$this->assertPatternMatchesSchema( $prepared_pattern );
@@ -434,7 +425,7 @@ public function test_get_item_schema() {
 	 * @param bool      $assert_same    Assertion type (assertSame vs assertNotSame).
 	 */
 	public function test_transient_keys_get_generated_correctly( $parameters_1, $parameters_2, $message, $assert_same = true ) {
-		$reflection_method = new ReflectionMethod( $this->controller, 'get_transient_key' );
+		$reflection_method = new ReflectionMethod( static::$controller, 'get_transient_key' );
 		$reflection_method->setAccessible( true );
 
 		$result_1 = $reflection_method->invoke( self::$controller, $parameters_1 );

From 2c08eeab216148827b02aa5f99a309948ca31a3b Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Wed, 27 Apr 2022 19:45:22 +0200
Subject: [PATCH 16/21] Use serialize instead of implode because transient keys
 must depend on request keys.

---
 ...s-wp-rest-pattern-directory-controller.php |  8 +++-----
 .../rest-pattern-directory-controller.php     | 20 +++++++++++++++++++
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
index 4e11ef78bd6b5..8db9eb7f2f824 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
@@ -367,14 +367,12 @@ protected function get_transient_key( $query_args ) {
 			// Sort the array so that the transient key doesn't depend on the order of slugs.
 			sort( $query_args['slug'] );
 
-			// Slugs have to be imploded separately as implode doesn't work with recursive arrays.
-			$query_args['slug'] = implode( ',', $query_args['slug'] );
-
-			if ( '' === trim( $query_args['slug'] ) ) {
+			// Empty arrays should not affect the transient key.
+			if ( 0 === count( $query_args['slug'] ) ) {
 				unset( $query_args['slug'] );
 			}
 		}
 
-		return 'wp_remote_block_patterns_' . md5( implode( '-', $query_args ) );
+		return 'wp_remote_block_patterns_' . md5( serialize( $query_args ) );
 	}
 }
diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index 807037da86484..734e452bc0d69 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -473,6 +473,16 @@ public function data_get_query_parameters() {
 				),
 				'message' => 'The order of slugs should not affect transient key.',
 			),
+			array(
+				array(
+					'parameter_1' => 1,
+					'slug'        => array(),
+				),
+				array(
+					'parameter_1' => 1,
+				),
+				'message' => 'Transient keys must match.',
+			),
 			array(
 				array(
 					'parameter_1' => 1,
@@ -485,6 +495,16 @@ public function data_get_query_parameters() {
 				'message' => 'Transient keys must not match.',
 				false,
 			),
+			array(
+				array(
+					'parameter_1' => 1,
+				),
+				array(
+					'parameter_2' => 1,
+				),
+				'message' => 'Transient keys must depend on array keys.',
+				false,
+			),
 		);
 	}
 

From 0411a8126f16dac6d7e7dd730cdd4a2b7cbacf33 Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Fri, 29 Apr 2022 15:49:34 +0200
Subject: [PATCH 17/21] Improve
 WP_REST_Pattern_Directory_Controller_Test::test_transient_keys_get_generated_correctly:
 add error messages.

---
 .../tests/rest-api/rest-pattern-directory-controller.php  | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index 734e452bc0d69..67f4b6b642723 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -431,11 +431,11 @@ public function test_transient_keys_get_generated_correctly( $parameters_1, $par
 		$result_1 = $reflection_method->invoke( self::$controller, $parameters_1 );
 		$result_2 = $reflection_method->invoke( self::$controller, $parameters_2 );
 
-		$this->assertIsString( $result_1 );
-		$this->assertNotEmpty( $result_1 );
+		$this->assertIsString( $result_1, 'The transient key must be a string.' );
+		$this->assertNotEmpty( $result_1, 'The transient key must not be empty.' );
 
-		$this->assertIsString( $result_2 );
-		$this->assertNotEmpty( $result_2 );
+		$this->assertIsString( $result_2, 'The transient key must be a string.' );
+		$this->assertNotEmpty( $result_2, 'The transient key must not be empty.' );
 
 		if ( $assert_same ) {
 			$this->assertSame( $result_1, $result_2, $message );

From 5653f25aa2893fc715d5dd9be6ecd7483aa83e64 Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Fri, 29 Apr 2022 15:52:13 +0200
Subject: [PATCH 18/21] Improve
 WP_REST_Pattern_Directory_Controller_Test::test_transient_keys_get_generated_correctly:
 add error messages.

---
 .../tests/rest-api/rest-pattern-directory-controller.php  | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index 67f4b6b642723..c0ff680d36c53 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -431,11 +431,11 @@ public function test_transient_keys_get_generated_correctly( $parameters_1, $par
 		$result_1 = $reflection_method->invoke( self::$controller, $parameters_1 );
 		$result_2 = $reflection_method->invoke( self::$controller, $parameters_2 );
 
-		$this->assertIsString( $result_1, 'The transient key must be a string.' );
-		$this->assertNotEmpty( $result_1, 'The transient key must not be empty.' );
+		$this->assertIsString( $result_1, 'Transient key #1 must be a string.' );
+		$this->assertNotEmpty( $result_1, 'Transient key #1 must not be empty.' );
 
-		$this->assertIsString( $result_2, 'The transient key must be a string.' );
-		$this->assertNotEmpty( $result_2, 'The transient key must not be empty.' );
+		$this->assertIsString( $result_2, 'Transient key #2 must be a string.' );
+		$this->assertNotEmpty( $result_2, 'Transient key #2 must not be empty.' );
 
 		if ( $assert_same ) {
 			$this->assertSame( $result_1, $result_2, $message );

From 0879fe08723b153db98a7db5762e4d9a8898a107 Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Fri, 29 Apr 2022 16:20:55 +0200
Subject: [PATCH 19/21] Update the test per @costdev 's suggestion.

---
 .../rest-pattern-directory-controller.php     | 20 +++++--------------
 1 file changed, 5 insertions(+), 15 deletions(-)

diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index c0ff680d36c53..2ab0f6b14c32a 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -452,7 +452,7 @@ public function test_transient_keys_get_generated_correctly( $parameters_1, $par
 	 */
 	public function data_get_query_parameters() {
 		return array(
-			array(
+			'same key and empty slugs'              => array(
 				array(
 					'parameter_1' => 1,
 					'slug'        => array(),
@@ -462,7 +462,7 @@ public function data_get_query_parameters() {
 				),
 				'Empty slugs should not affect the transient key.',
 			),
-			array(
+			'same key and slugs in different order' => array(
 				array(
 					'parameter_1' => 1,
 					'slug'        => array( 0, 2 ),
@@ -471,19 +471,9 @@ public function data_get_query_parameters() {
 					'parameter_1' => 1,
 					'slug'        => array( 2, 0 ),
 				),
-				'message' => 'The order of slugs should not affect transient key.',
+				'message' => 'The order of slugs should not affect the transient key.',
 			),
-			array(
-				array(
-					'parameter_1' => 1,
-					'slug'        => array(),
-				),
-				array(
-					'parameter_1' => 1,
-				),
-				'message' => 'Transient keys must match.',
-			),
-			array(
+			'same key and different slugs'          => array(
 				array(
 					'parameter_1' => 1,
 					'slug'        => array( 'some_slug' ),
@@ -495,7 +485,7 @@ public function data_get_query_parameters() {
 				'message' => 'Transient keys must not match.',
 				false,
 			),
-			array(
+			'different keys'                        => array(
 				array(
 					'parameter_1' => 1,
 				),

From 8ec23a091f7a4b2b640f651da0265d78b136ca52 Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Fri, 29 Apr 2022 16:26:27 +0200
Subject: [PATCH 20/21] Update the test per @costdev 's suggestion.

---
 .../rest-pattern-directory-controller.php     | 24 +++++++++----------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
index 2ab0f6b14c32a..43ca497edbd40 100644
--- a/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
+++ b/tests/phpunit/tests/rest-api/rest-pattern-directory-controller.php
@@ -453,46 +453,46 @@ public function test_transient_keys_get_generated_correctly( $parameters_1, $par
 	public function data_get_query_parameters() {
 		return array(
 			'same key and empty slugs'              => array(
-				array(
+				'parameters_1' => array(
 					'parameter_1' => 1,
 					'slug'        => array(),
 				),
-				array(
+				'parameters_2' => array(
 					'parameter_1' => 1,
 				),
-				'Empty slugs should not affect the transient key.',
+				'message'      => 'Empty slugs should not affect the transient key.',
 			),
 			'same key and slugs in different order' => array(
-				array(
+				'parameters_1' => array(
 					'parameter_1' => 1,
 					'slug'        => array( 0, 2 ),
 				),
-				array(
+				'parameters_2' => array(
 					'parameter_1' => 1,
 					'slug'        => array( 2, 0 ),
 				),
-				'message' => 'The order of slugs should not affect the transient key.',
+				'message'      => 'The order of slugs should not affect the transient key.',
 			),
 			'same key and different slugs'          => array(
-				array(
+				'parameters_1' => array(
 					'parameter_1' => 1,
 					'slug'        => array( 'some_slug' ),
 				),
-				array(
+				'parameters_2' => array(
 					'parameter_1' => 1,
 					'slug'        => array( 'some_other_slug' ),
 				),
-				'message' => 'Transient keys must not match.',
+				'message'      => 'Transient keys must not match.',
 				false,
 			),
 			'different keys'                        => array(
-				array(
+				'parameters_1' => array(
 					'parameter_1' => 1,
 				),
-				array(
+				'parameters_2' => array(
 					'parameter_2' => 1,
 				),
-				'message' => 'Transient keys must depend on array keys.',
+				'message'      => 'Transient keys must depend on array keys.',
 				false,
 			),
 		);

From 1d8f893540d5fb7755444376d606059cfd677508 Mon Sep 17 00:00:00 2001
From: Anton Vlasenko <vlasenko.anton@gmail.com>
Date: Mon, 2 May 2022 15:02:25 +0200
Subject: [PATCH 21/21] Micro-optimisations per @hellofromtonya 's suggestion
 here:
 https://github.com/WordPress/wordpress-develop/pull/2625#discussion_r862808359

---
 .../class-wp-rest-pattern-directory-controller.php        | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
index 8db9eb7f2f824..8e5f063cd5024 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-pattern-directory-controller.php
@@ -364,12 +364,12 @@ protected function get_transient_key( $query_args ) {
 			// This is an additional precaution because the "sort" function expects an array.
 			$query_args['slug'] = wp_parse_list( $query_args['slug'] );
 
-			// Sort the array so that the transient key doesn't depend on the order of slugs.
-			sort( $query_args['slug'] );
-
 			// Empty arrays should not affect the transient key.
-			if ( 0 === count( $query_args['slug'] ) ) {
+			if ( empty( $query_args['slug'] ) ) {
 				unset( $query_args['slug'] );
+			} else {
+				// Sort the array so that the transient key doesn't depend on the order of slugs.
+				sort( $query_args['slug'] );
 			}
 		}