From a52381d9f599748a24ea4c9edcb022f7cb7a65ef Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Wed, 21 Aug 2024 15:19:31 -0700
Subject: [PATCH 01/16] Allow URL metric schema to be extended

---
 .../class-od-url-metric.php                   | 102 ++++++++-
 .../tests/test-class-od-url-metric.php        | 194 +++++++++++++++++-
 2 files changed, 286 insertions(+), 10 deletions(-)

diff --git a/plugins/optimization-detective/class-od-url-metric.php b/plugins/optimization-detective/class-od-url-metric.php
index 83eca93e81..a0971c5759 100644
--- a/plugins/optimization-detective/class-od-url-metric.php
+++ b/plugins/optimization-detective/class-od-url-metric.php
@@ -121,7 +121,7 @@ public static function get_json_schema(): array {
 		 * Note that 'number' is used specifically instead of 'integer' because the values are all specified as
 		 * floats/doubles.
 		 */
-		$properties = array_fill_keys(
+		$dom_rect_properties = array_fill_keys(
 			array(
 				'width',
 				'height',
@@ -139,17 +139,17 @@ public static function get_json_schema(): array {
 		);
 
 		// The spec allows these to be negative but this doesn't make sense in the context of intersectionRect and boundingClientRect.
-		$properties['width']['minimum']  = 0.0;
-		$properties['height']['minimum'] = 0.0;
+		$dom_rect_properties['width']['minimum']  = 0.0;
+		$dom_rect_properties['height']['minimum'] = 0.0;
 
 		$dom_rect_schema = array(
 			'type'                 => 'object',
 			'required'             => true,
-			'properties'           => $properties,
+			'properties'           => $dom_rect_properties,
 			'additionalProperties' => false,
 		);
 
-		return array(
+		$schema = array(
 			'$schema'              => 'http://json-schema.org/draft-04/schema#',
 			'title'                => 'od-url-metric',
 			'type'                 => 'object',
@@ -231,6 +231,98 @@ public static function get_json_schema(): array {
 			),
 			'additionalProperties' => false,
 		);
+
+		/**
+		 * Filters additional schema properties which should be allowed at the root of a URL metric.
+		 *
+		 * @since n.e.x.t
+		 *
+		 * @param array<string, array{type: string}> $additional_properties Additional properties.
+		 */
+		$additional_properties = (array) apply_filters( 'od_url_metric_schema_root_additional_properties', array() );
+		if ( count( $additional_properties ) > 0 ) {
+			$schema['properties'] = self::extend_schema_with_optional_properties( $schema['properties'], $additional_properties, 'od_url_metric_schema_root_additional_properties' );
+		}
+
+		/**
+		 * Filters additional schema properties which should be allowed for an elements item in a URL metric.
+		 *
+		 * @since n.e.x.t
+		 *
+		 * @param array<string, array{type: string}> $additional_properties Additional properties.
+		 */
+		$additional_properties = (array) apply_filters( 'od_url_metric_schema_element_item_additional_properties', array() );
+		if ( count( $additional_properties ) > 0 ) {
+			$schema['properties']['elements']['items']['properties'] = self::extend_schema_with_optional_properties(
+				$schema['properties']['elements']['items']['properties'],
+				$additional_properties,
+				'od_url_metric_schema_root_additional_properties'
+			);
+		}
+
+		return $schema;
+	}
+
+	/**
+	 * Extends a schema with additional optional properties.
+	 *
+	 * @since n.e.x.t
+	 *
+	 * @param array<string, mixed> $properties_schema     Properties schema to extend.
+	 * @param array<string, mixed> $additional_properties Additional properties.
+	 * @param string               $filter_name           Filter name used to extend.
+	 *
+	 * @return array<string, mixed> Extended schema.
+	 */
+	protected static function extend_schema_with_optional_properties( array $properties_schema, array $additional_properties, string $filter_name ): array {
+		$doing_it_wrong = static function ( string $message ) use ( $filter_name ): void {
+			_doing_it_wrong(
+				esc_html( "add_filter({$filter_name},...)" ),
+				esc_html( $message ),
+				'Optimization Detective n.e.x.t'
+			);
+		};
+		foreach ( $additional_properties as $property_key => $property_schema ) {
+			if ( ! is_array( $property_schema ) ) {
+				continue;
+			}
+			if ( isset( $properties_schema[ $property_key ] ) ) {
+				$doing_it_wrong(
+					sprintf(
+						/* translators: property name */
+						__( 'Disallowed override of existing schema property "%s".', 'optimization-detective' ),
+						$property_key
+					)
+				);
+				continue;
+			}
+			if ( ! isset( $property_schema['type'] ) || ! is_string( $property_schema['type'] ) ) {
+				$doing_it_wrong(
+					sprintf(
+						/* translators: 1: property name, 2: 'type' */
+						__( 'Supplied schema property "%1$s" with missing "%2$s" key.', 'optimization-detective' ),
+						'type',
+						$property_key
+					)
+				);
+				continue;
+			}
+			// TODO: Should 'default' be required?
+			if ( isset( $property_schema['required'] ) && false !== $property_schema['required'] ) {
+				$doing_it_wrong(
+					sprintf(
+						/* translators: 1: property name, 2: 'required' */
+						__( 'Supplied schema property "%1$s" with truthy for "%2$s". All properties must be optional.', 'optimization-detective' ),
+						'type',
+						$property_key
+					)
+				);
+			}
+			$property_schema['required'] = false;
+
+			$properties_schema[ $property_key ] = $property_schema;
+		}
+		return $properties_schema;
 	}
 
 	/**
diff --git a/plugins/optimization-detective/tests/test-class-od-url-metric.php b/plugins/optimization-detective/tests/test-class-od-url-metric.php
index d301997d58..6a09d4fe6d 100644
--- a/plugins/optimization-detective/tests/test-class-od-url-metric.php
+++ b/plugins/optimization-detective/tests/test-class-od-url-metric.php
@@ -215,7 +215,189 @@ public function test_constructor( array $data, string $error = '' ): void {
 	 */
 	public function test_get_json_schema(): void {
 		$schema = OD_URL_Metric::get_json_schema();
-		$this->check_schema_subset( $schema, 'root' );
+		$this->check_schema_subset( $schema, 'root', false );
+	}
+
+	/**
+	 * Data provider.
+	 *
+	 * @return array<string, mixed>
+	 */
+	public function data_provider_to_test_get_json_schema_extensibility(): array {
+		return array(
+			'missing_type'                   => array(
+				'set_up'                   => static function (): void {
+					add_filter(
+						'od_url_metric_schema_root_additional_properties',
+						static function ( $additional_properties ) {
+							$additional_properties['foo'] = array(
+								'missing',
+							);
+							return $additional_properties;
+						}
+					);
+				},
+				'assert'                   => function ( array $original_schema, $extended_schema ): void {
+					$this->assertSame( $original_schema, $extended_schema );
+				},
+				'expected_incorrect_usage' => 'add_filter(od_url_metric_schema_root_additional_properties,...)',
+			),
+
+			'bad_type'                       => array(
+				'set_up'                   => static function (): void {
+					add_filter(
+						'od_url_metric_schema_root_additional_properties',
+						static function ( $additional_properties ) {
+							$additional_properties['foo'] = array(
+								'type' => 123,
+							);
+							return $additional_properties;
+						}
+					);
+				},
+				'assert'                   => function ( array $original_schema, $extended_schema ): void {
+					$this->assertSame( $original_schema, $extended_schema );
+				},
+				'expected_incorrect_usage' => 'add_filter(od_url_metric_schema_root_additional_properties,...)',
+			),
+
+			'bad_required'                   => array(
+				'set_up'                   => static function (): void {
+					add_filter(
+						'od_url_metric_schema_root_additional_properties',
+						static function ( $additional_properties ) {
+							$additional_properties['foo'] = array(
+								'type'     => 'string',
+								'required' => true,
+							);
+							return $additional_properties;
+						}
+					);
+				},
+				'assert'                   => function ( array $original_schema, $extended_schema ): void {
+					$expected_schema = $original_schema;
+					$expected_schema['properties']['foo'] = array(
+						'type'     => 'string',
+						'required' => false,
+					);
+					$this->assertSame( $expected_schema, $extended_schema );
+				},
+				'expected_incorrect_usage' => 'add_filter(od_url_metric_schema_root_additional_properties,...)',
+			),
+
+			'bad_existing_root_property'     => array(
+				'set_up'                   => static function (): void {
+					add_filter(
+						'od_url_metric_schema_root_additional_properties',
+						static function ( $additional_properties ) {
+							$additional_properties['uuid'] = array(
+								'type' => 'number',
+							);
+							return $additional_properties;
+						}
+					);
+				},
+				'assert'                   => function ( array $original_schema, $extended_schema ): void {
+					$this->assertSame( $original_schema, $extended_schema );
+				},
+				'expected_incorrect_usage' => 'add_filter(od_url_metric_schema_root_additional_properties,...)',
+			),
+
+			'bad_existing_element_property'  => array(
+				'set_up'                   => static function (): void {
+					add_filter(
+						'od_url_metric_schema_element_item_additional_properties',
+						static function ( $additional_properties ) {
+							$additional_properties['intersectionRatio'] = array(
+								'type' => 'string',
+							);
+							return $additional_properties;
+						}
+					);
+				},
+				'assert'                   => function ( array $original_schema, $extended_schema ): void {
+					$this->assertSame( $original_schema, $extended_schema );
+				},
+				'expected_incorrect_usage' => 'add_filter(od_url_metric_schema_root_additional_properties,...)',
+			),
+
+			'adding_root_string'             => array(
+				'set_up'                   => static function (): void {
+					add_filter(
+						'od_url_metric_schema_root_additional_properties',
+						static function ( $additional_properties ) {
+							$additional_properties['foo'] = array(
+								'type' => 'string',
+							);
+							return $additional_properties;
+						}
+					);
+				},
+				'assert'                   => function ( array $original_schema, $extended_schema ): void {
+					$expected_schema = $original_schema;
+					$expected_schema['properties']['foo'] = array(
+						'type'     => 'string',
+						'required' => false,
+					);
+					$this->assertSame( $expected_schema, $extended_schema );
+				},
+				'expected_incorrect_usage' => null,
+			),
+
+			'adding_root_and_element_string' => array(
+				'set_up'                   => static function (): void {
+					add_filter(
+						'od_url_metric_schema_root_additional_properties',
+						static function ( $additional_properties ) {
+							$additional_properties['foo'] = array(
+								'type' => 'string',
+							);
+							return $additional_properties;
+						}
+					);
+					add_filter(
+						'od_url_metric_schema_element_item_additional_properties',
+						static function ( $additional_properties ) {
+							$additional_properties['bar'] = array(
+								'type' => 'number',
+							);
+							return $additional_properties;
+						}
+					);
+				},
+				'assert'                   => function ( array $original_schema, $extended_schema ): void {
+					$expected_schema = $original_schema;
+					$expected_schema['properties']['foo'] = array(
+						'type'     => 'string',
+						'required' => false,
+					);
+					$expected_schema['properties']['elements']['items']['properties']['bar'] = array(
+						'type'     => 'number',
+						'required' => false,
+					);
+					$this->assertSame( $expected_schema, $extended_schema );
+				},
+				'expected_incorrect_usage' => null,
+			),
+		);
+	}
+
+	/**
+	 * Tests get_json_schema() extensibility.
+	 *
+	 * @dataProvider data_provider_to_test_get_json_schema_extensibility
+	 *
+	 * @covers ::get_json_schema
+	 */
+	public function test_get_json_schema_extensibility( Closure $set_up, Closure $assert, ?string $expected_incorrect_usage ): void {
+		if ( null !== $expected_incorrect_usage ) {
+			$this->setExpectedIncorrectUsage( $expected_incorrect_usage );
+		}
+		$original_schema = OD_URL_Metric::get_json_schema();
+		$set_up();
+		$extended_schema = OD_URL_Metric::get_json_schema();
+		$this->check_schema_subset( $extended_schema, 'root', true );
+		$assert( $original_schema, $extended_schema );
 	}
 
 	/**
@@ -223,20 +405,22 @@ public function test_get_json_schema(): void {
 	 *
 	 * @param array<string, mixed> $schema Schema subset.
 	 */
-	protected function check_schema_subset( array $schema, string $path ): void {
+	protected function check_schema_subset( array $schema, string $path, bool $extended = false ): void {
 		$this->assertArrayHasKey( 'required', $schema, $path );
-		$this->assertTrue( $schema['required'], $path );
+		if ( ! $extended ) {
+			$this->assertTrue( $schema['required'], $path );
+		}
 		$this->assertArrayHasKey( 'type', $schema, $path );
 		if ( 'object' === $schema['type'] ) {
 			$this->assertArrayHasKey( 'properties', $schema, $path );
 			$this->assertArrayHasKey( 'additionalProperties', $schema, $path );
 			$this->assertFalse( $schema['additionalProperties'] );
 			foreach ( $schema['properties'] as $key => $property_schema ) {
-				$this->check_schema_subset( $property_schema, "$path/$key" );
+				$this->check_schema_subset( $property_schema, "$path/$key", $extended );
 			}
 		} elseif ( 'array' === $schema['type'] ) {
 			$this->assertArrayHasKey( 'items', $schema, $path );
-			$this->check_schema_subset( $schema['items'], "$path/items" );
+			$this->check_schema_subset( $schema['items'], "$path/items", $extended );
 		}
 	}
 }

From e244b22f52b9ccf1044f193962cec3ade082d40f Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Wed, 21 Aug 2024 15:56:24 -0700
Subject: [PATCH 02/16] Add get() and __get() methods to OD_URL_Metric

Co-authored-by: felixarntz <flixos90@git.wordpress.org>
---
 .../class-od-url-metric.php                   | 36 +++++++++++++++++++
 .../tests/test-class-od-url-metric.php        | 20 +++++++++++
 2 files changed, 56 insertions(+)

diff --git a/plugins/optimization-detective/class-od-url-metric.php b/plugins/optimization-detective/class-od-url-metric.php
index a0971c5759..4c4db37711 100644
--- a/plugins/optimization-detective/class-od-url-metric.php
+++ b/plugins/optimization-detective/class-od-url-metric.php
@@ -44,6 +44,12 @@
  *                                elements: ElementData[]
  *                            }
  *
+ * @property-read string        $uuid
+ * @property-read string        $url
+ * @property-read float         $timestamp
+ * @property-read ViewportRect  $viewport
+ * @property-read ElementData[] $elements
+ *
  * @since 0.1.0
  * @access private
  */
@@ -325,6 +331,36 @@ protected static function extend_schema_with_optional_properties( array $propert
 		return $properties_schema;
 	}
 
+	/**
+	 * Gets property value for an arbitrary key.
+	 *
+	 * This is particularly useful in conjunction with the `od_url_metric_schema_root_additional_properties` filter.
+	 *
+	 * @since n.e.x.t
+	 * @todo Instead of returning null when the key doesn't exist, should the `default` value be returned as defined in the schema?
+	 *
+	 * @param string $key Property.
+	 * @return mixed|null
+	 */
+	public function get( string $key ) {
+		return $this->data[ $key ] ?? null;
+	}
+
+	/**
+	 * Gets property value for an arbitrary key.
+	 *
+	 * This is useful with the `@property-read` annotations for the class. For accessing other data,
+	 * it's likely the `get()` method will be more useful for static analysis reasons.
+	 *
+	 * @since n.e.x.t
+	 *
+	 * @param string $key Property.
+	 * @return mixed|null
+	 */
+	public function __get( string $key ) {
+		return $this->get( $key );
+	}
+
 	/**
 	 * Gets UUID.
 	 *
diff --git a/plugins/optimization-detective/tests/test-class-od-url-metric.php b/plugins/optimization-detective/tests/test-class-od-url-metric.php
index 6a09d4fe6d..5d32154cbe 100644
--- a/plugins/optimization-detective/tests/test-class-od-url-metric.php
+++ b/plugins/optimization-detective/tests/test-class-od-url-metric.php
@@ -178,6 +178,8 @@ public function data_provider(): array {
 	/**
 	 * Tests construction.
 	 *
+	 * @todo PHPStan complains when adding @covers tags for `::get()` and `::__get()` saying they are invalid method references.
+	 *
 	 * @covers ::get_viewport
 	 * @covers ::get_viewport_width
 	 * @covers ::get_timestamp
@@ -195,11 +197,29 @@ public function test_constructor( array $data, string $error = '' ): void {
 			$this->expectExceptionMessage( $error );
 		}
 		$url_metric = new OD_URL_Metric( $data );
+
 		$this->assertSame( $data['viewport'], $url_metric->get_viewport() );
+		$this->assertSame( $data['viewport'], $url_metric->get( 'viewport' ) );
+		$this->assertSame( $data['viewport'], $url_metric->viewport );
 		$this->assertSame( $data['viewport']['width'], $url_metric->get_viewport_width() );
+		$this->assertSame( $data['viewport']['width'], $url_metric->viewport['width'] );
+
 		$this->assertSame( $data['timestamp'], $url_metric->get_timestamp() );
+		$this->assertSame( $data['timestamp'], $url_metric->get( 'timestamp' ) );
+		$this->assertSame( $data['timestamp'], $url_metric->timestamp );
+
 		$this->assertSame( $data['elements'], $url_metric->get_elements() );
+		$this->assertSame( $data['elements'], $url_metric->get( 'elements' ) );
+		$this->assertSame( $data['elements'], $url_metric->elements );
+
+		$this->assertSame( $data['url'], $url_metric->get_url() );
+		$this->assertSame( $data['url'], $url_metric->get( 'url' ) );
+		$this->assertSame( $data['url'], $url_metric->url );
+
 		$this->assertTrue( wp_is_uuid( $url_metric->get_uuid() ) );
+		$this->assertSame( $url_metric->get_uuid(), $url_metric->uuid );
+		$this->assertSame( $url_metric->get_uuid(), $url_metric->get( 'uuid' ) );
+
 		$serialized = $url_metric->jsonSerialize();
 		if ( ! array_key_exists( 'uuid', $data ) ) {
 			$this->assertTrue( wp_is_uuid( $serialized['uuid'] ) );

From 079e6d9f082cc7c98887052ed8710e1e6f35a063 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Thu, 22 Aug 2024 09:44:56 -0700
Subject: [PATCH 03/16] Account for type being an array

---
 plugins/optimization-detective/class-od-url-metric.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/plugins/optimization-detective/class-od-url-metric.php b/plugins/optimization-detective/class-od-url-metric.php
index 4c4db37711..bb71a51ac1 100644
--- a/plugins/optimization-detective/class-od-url-metric.php
+++ b/plugins/optimization-detective/class-od-url-metric.php
@@ -302,7 +302,7 @@ protected static function extend_schema_with_optional_properties( array $propert
 				);
 				continue;
 			}
-			if ( ! isset( $property_schema['type'] ) || ! is_string( $property_schema['type'] ) ) {
+			if ( ! isset( $property_schema['type'] ) || ! ( is_string( $property_schema['type'] ) || is_array( $property_schema['type'] ) ) ) {
 				$doing_it_wrong(
 					sprintf(
 						/* translators: 1: property name, 2: 'type' */

From bbc97dc350a71babb9c477c90a1fe21c2e46cb33 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Thu, 22 Aug 2024 12:23:36 -0700
Subject: [PATCH 04/16] Add od_url_metric_collected action

---
 .../storage/rest-api.php                      | 27 +++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/plugins/optimization-detective/storage/rest-api.php b/plugins/optimization-detective/storage/rest-api.php
index fb16ed1441..13348a7677 100644
--- a/plugins/optimization-detective/storage/rest-api.php
+++ b/plugins/optimization-detective/storage/rest-api.php
@@ -161,6 +161,33 @@ function od_handle_rest_request( WP_REST_Request $request ) {
 	if ( $result instanceof WP_Error ) {
 		return $result;
 	}
+	$post_id = $result;
+
+	/**
+	 * Fires whenever a URL Metric was successfully collected.
+	 *
+	 * @since n.e.x.t
+	 *
+	 * @param array $context {
+	 *     Context about the successful URL Metric collection.
+	 *
+	 *     @var int                                   $post_id
+	 *     @var WP_REST_Request<array<string, mixed>> $request
+	 *     @var OD_URL_Metric                         $url_metric
+	 *     @var OD_URL_Metrics_Group                  $group
+	 *     @var OD_URL_Metrics_Group_Collection       $group_collection
+	 * }
+	 */
+	do_action(
+		'od_url_metric_collected',
+		array(
+			'post_id'                      => $post_id,
+			'request'                      => $request,
+			'url_metric'                   => $url_metric,
+			'url_metrics_group'            => $group,
+			'url_metrics_group_collection' => $group_collection,
+		)
+	);
 
 	return new WP_REST_Response(
 		array(

From 70fd8258521933305c91ee123d025953c11a5531 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Thu, 22 Aug 2024 12:24:11 -0700
Subject: [PATCH 05/16] Add todos related to store_url_metric()

---
 .../storage/class-od-url-metrics-post-type.php                   | 1 +
 plugins/optimization-detective/storage/rest-api.php              | 1 +
 2 files changed, 2 insertions(+)

diff --git a/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php b/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
index d51fbd450c..43079459a1 100644
--- a/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
+++ b/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
@@ -188,6 +188,7 @@ static function ( $url_metric_data ) use ( $trigger_error ) {
 	 * Stores URL metric by merging it with the other URL metrics which share the same normalized query vars.
 	 *
 	 * @since 0.1.0
+	 * @todo There is duplicate logic here with od_handle_rest_request().
 	 *
 	 * @param string        $slug           Slug (hash of normalized query vars).
 	 * @param OD_URL_Metric $new_url_metric New URL metric.
diff --git a/plugins/optimization-detective/storage/rest-api.php b/plugins/optimization-detective/storage/rest-api.php
index 13348a7677..17a2e4fc1d 100644
--- a/plugins/optimization-detective/storage/rest-api.php
+++ b/plugins/optimization-detective/storage/rest-api.php
@@ -153,6 +153,7 @@ function od_handle_rest_request( WP_REST_Request $request ) {
 		);
 	}
 
+	// TODO: This should be changed from store_url_metric($slug, $url_metric) instead be update_post( $slug, $group_collection ). As it stands, store_url_metric() is duplicating logic here.
 	$result = OD_URL_Metrics_Post_Type::store_url_metric(
 		$request->get_param( 'slug' ),
 		$url_metric

From 381c829ceea2417e422dd7b7d498273153641c0b Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Fri, 6 Sep 2024 12:57:11 -0700
Subject: [PATCH 06/16] Adopt Yoast SEO scheme for filter _doing_it_wrong

---
 plugins/optimization-detective/class-od-url-metric.php |  2 +-
 .../tests/test-class-od-url-metric.php                 | 10 +++++-----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/plugins/optimization-detective/class-od-url-metric.php b/plugins/optimization-detective/class-od-url-metric.php
index bb71a51ac1..d5667da888 100644
--- a/plugins/optimization-detective/class-od-url-metric.php
+++ b/plugins/optimization-detective/class-od-url-metric.php
@@ -283,7 +283,7 @@ public static function get_json_schema(): array {
 	protected static function extend_schema_with_optional_properties( array $properties_schema, array $additional_properties, string $filter_name ): array {
 		$doing_it_wrong = static function ( string $message ) use ( $filter_name ): void {
 			_doing_it_wrong(
-				esc_html( "add_filter({$filter_name},...)" ),
+				esc_html( "Filter: '{$filter_name}'" ),
 				esc_html( $message ),
 				'Optimization Detective n.e.x.t'
 			);
diff --git a/plugins/optimization-detective/tests/test-class-od-url-metric.php b/plugins/optimization-detective/tests/test-class-od-url-metric.php
index 5d32154cbe..0aa636f3c3 100644
--- a/plugins/optimization-detective/tests/test-class-od-url-metric.php
+++ b/plugins/optimization-detective/tests/test-class-od-url-metric.php
@@ -260,7 +260,7 @@ static function ( $additional_properties ) {
 				'assert'                   => function ( array $original_schema, $extended_schema ): void {
 					$this->assertSame( $original_schema, $extended_schema );
 				},
-				'expected_incorrect_usage' => 'add_filter(od_url_metric_schema_root_additional_properties,...)',
+				'expected_incorrect_usage' => 'Filter: &#039;od_url_metric_schema_root_additional_properties&#039;',
 			),
 
 			'bad_type'                       => array(
@@ -278,7 +278,7 @@ static function ( $additional_properties ) {
 				'assert'                   => function ( array $original_schema, $extended_schema ): void {
 					$this->assertSame( $original_schema, $extended_schema );
 				},
-				'expected_incorrect_usage' => 'add_filter(od_url_metric_schema_root_additional_properties,...)',
+				'expected_incorrect_usage' => 'Filter: &#039;od_url_metric_schema_root_additional_properties&#039;',
 			),
 
 			'bad_required'                   => array(
@@ -302,7 +302,7 @@ static function ( $additional_properties ) {
 					);
 					$this->assertSame( $expected_schema, $extended_schema );
 				},
-				'expected_incorrect_usage' => 'add_filter(od_url_metric_schema_root_additional_properties,...)',
+				'expected_incorrect_usage' => 'Filter: &#039;od_url_metric_schema_root_additional_properties&#039;',
 			),
 
 			'bad_existing_root_property'     => array(
@@ -320,7 +320,7 @@ static function ( $additional_properties ) {
 				'assert'                   => function ( array $original_schema, $extended_schema ): void {
 					$this->assertSame( $original_schema, $extended_schema );
 				},
-				'expected_incorrect_usage' => 'add_filter(od_url_metric_schema_root_additional_properties,...)',
+				'expected_incorrect_usage' => 'Filter: &#039;od_url_metric_schema_root_additional_properties&#039;',
 			),
 
 			'bad_existing_element_property'  => array(
@@ -338,7 +338,7 @@ static function ( $additional_properties ) {
 				'assert'                   => function ( array $original_schema, $extended_schema ): void {
 					$this->assertSame( $original_schema, $extended_schema );
 				},
-				'expected_incorrect_usage' => 'add_filter(od_url_metric_schema_root_additional_properties,...)',
+				'expected_incorrect_usage' => 'Filter: &#039;od_url_metric_schema_root_additional_properties&#039;',
 			),
 
 			'adding_root_string'             => array(

From e85c68337419bc512dd5f80cfed1c6e4f67a6b29 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Fri, 6 Sep 2024 15:00:32 -0700
Subject: [PATCH 07/16] Fix and clarify message for disallowed required
 property in extended schema

---
 plugins/optimization-detective/class-od-url-metric.php | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/plugins/optimization-detective/class-od-url-metric.php b/plugins/optimization-detective/class-od-url-metric.php
index d5667da888..5717d1b24e 100644
--- a/plugins/optimization-detective/class-od-url-metric.php
+++ b/plugins/optimization-detective/class-od-url-metric.php
@@ -318,9 +318,9 @@ protected static function extend_schema_with_optional_properties( array $propert
 				$doing_it_wrong(
 					sprintf(
 						/* translators: 1: property name, 2: 'required' */
-						__( 'Supplied schema property "%1$s" with truthy for "%2$s". All properties must be optional.', 'optimization-detective' ),
-						'type',
-						$property_key
+						__( 'Supplied schema property "%1$s" has a truthy value for "%2$s". All extended properties must be optional so that URL Metrics are not all immediately invalidated once an extension is deactivated..', 'optimization-detective' ),
+						$property_key,
+						'required'
 					)
 				);
 			}

From 0cc91030d50bd0979f05ae289eca7dd9100ffe2e Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Fri, 6 Sep 2024 16:58:44 -0700
Subject: [PATCH 08/16] Add sanitization in addition to validation to ensure
 expected PHP types

---
 .../class-od-url-metric.php                   | 19 +++----
 .../test-class-od-url-metrics-post-type.php   |  2 +-
 .../tests/test-class-od-url-metric.php        | 51 +++++++++++++++----
 3 files changed, 51 insertions(+), 21 deletions(-)

diff --git a/plugins/optimization-detective/class-od-url-metric.php b/plugins/optimization-detective/class-od-url-metric.php
index 5717d1b24e..44ea0b513c 100644
--- a/plugins/optimization-detective/class-od-url-metric.php
+++ b/plugins/optimization-detective/class-od-url-metric.php
@@ -67,28 +67,28 @@ final class OD_URL_Metric implements JsonSerializable {
 	 *
 	 * @phpstan-param Data|array<string, mixed> $data Valid data or invalid data (in which case an exception is thrown).
 	 *
-	 * @param array<string, mixed> $data URL metric data.
-	 *
 	 * @throws OD_Data_Validation_Exception When the input is invalid.
+	 *
+	 * @param array<string, mixed> $data URL metric data.
 	 */
 	public function __construct( array $data ) {
 		if ( ! isset( $data['uuid'] ) ) {
 			$data['uuid'] = wp_generate_uuid4();
 		}
-		$this->validate_data( $data );
-		$this->data = $data;
+		$this->data = $this->prepare_data( $data );
 	}
 
 	/**
-	 * Validate data.
+	 * Prepares data with validation and sanitization.
 	 *
-	 * @phpstan-assert Data $data
+	 * @throws OD_Data_Validation_Exception When the input is invalid.
 	 *
 	 * @param array<string, mixed> $data Data to validate.
-	 * @throws OD_Data_Validation_Exception When the input is invalid.
+	 * @return Data Validated and sanitized data.
 	 */
-	private function validate_data( array $data ): void {
-		$valid = rest_validate_object_value_from_schema( $data, self::get_json_schema(), self::class );
+	private function prepare_data( array $data ): array {
+		$schema = static::get_json_schema();
+		$valid  = rest_validate_object_value_from_schema( $data, $schema, self::class );
 		if ( is_wp_error( $valid ) ) {
 			throw new OD_Data_Validation_Exception( esc_html( $valid->get_error_message() ) );
 		}
@@ -111,6 +111,7 @@ private function validate_data( array $data ): void {
 				)
 			);
 		}
+		return rest_sanitize_value_from_schema( $data, $schema, self::class );
 	}
 
 	/**
diff --git a/plugins/optimization-detective/tests/storage/test-class-od-url-metrics-post-type.php b/plugins/optimization-detective/tests/storage/test-class-od-url-metrics-post-type.php
index 8872d13156..135595194c 100644
--- a/plugins/optimization-detective/tests/storage/test-class-od-url-metrics-post-type.php
+++ b/plugins/optimization-detective/tests/storage/test-class-od-url-metrics-post-type.php
@@ -94,7 +94,7 @@ public function data_provider_test_get_url_metrics_from_post(): array {
 					'width'  => 640,
 					'height' => 480,
 				),
-				'timestamp' => (int) microtime( true ), // Integer to facilitate equality tests.
+				'timestamp' => microtime( true ),
 				'elements'  => array(),
 			),
 		);
diff --git a/plugins/optimization-detective/tests/test-class-od-url-metric.php b/plugins/optimization-detective/tests/test-class-od-url-metric.php
index 0aa636f3c3..96a34baa2b 100644
--- a/plugins/optimization-detective/tests/test-class-od-url-metric.php
+++ b/plugins/optimization-detective/tests/test-class-od-url-metric.php
@@ -48,6 +48,26 @@ public function data_provider(): array {
 					),
 				),
 			),
+			// This tests that sanitization converts values into their expected PHP types.
+			'valid_but_props_are_strings'     => array(
+				'data' => array(
+					'url'       => home_url( '/' ),
+					'viewport'  => array_map( 'strval', $viewport ),
+					'timestamp' => (string) microtime( true ),
+					'elements'  => array(
+						array_map(
+							static function ( $value ) {
+								if ( is_array( $value ) ) {
+									return array_map( 'strval', $value );
+								} else {
+									return (string) $value;
+								}
+							},
+							$valid_element
+						),
+					),
+				),
+			),
 			'bad_uuid'                        => array(
 				'data'  => array(
 					'uuid'      => 'foo',
@@ -198,19 +218,26 @@ public function test_constructor( array $data, string $error = '' ): void {
 		}
 		$url_metric = new OD_URL_Metric( $data );
 
-		$this->assertSame( $data['viewport'], $url_metric->get_viewport() );
-		$this->assertSame( $data['viewport'], $url_metric->get( 'viewport' ) );
-		$this->assertSame( $data['viewport'], $url_metric->viewport );
-		$this->assertSame( $data['viewport']['width'], $url_metric->get_viewport_width() );
-		$this->assertSame( $data['viewport']['width'], $url_metric->viewport['width'] );
+		$this->assertSame( array_map( 'intval', $data['viewport'] ), $url_metric->get_viewport() );
+		$this->assertSame( array_map( 'intval', $data['viewport'] ), $url_metric->get( 'viewport' ) );
+		$this->assertSame( array_map( 'intval', $data['viewport'] ), $url_metric->viewport );
+		$this->assertSame( (int) $data['viewport']['width'], $url_metric->get_viewport_width() );
+		$this->assertSame( (int) $data['viewport']['width'], $url_metric->viewport['width'] );
 
-		$this->assertSame( $data['timestamp'], $url_metric->get_timestamp() );
-		$this->assertSame( $data['timestamp'], $url_metric->get( 'timestamp' ) );
-		$this->assertSame( $data['timestamp'], $url_metric->timestamp );
+		$this->assertSame( (float) $data['timestamp'], $url_metric->get_timestamp() );
+		$this->assertSame( (float) $data['timestamp'], $url_metric->get( 'timestamp' ) );
+		$this->assertSame( (float) $data['timestamp'], $url_metric->timestamp );
 
-		$this->assertSame( $data['elements'], $url_metric->get_elements() );
-		$this->assertSame( $data['elements'], $url_metric->get( 'elements' ) );
-		$this->assertSame( $data['elements'], $url_metric->elements );
+		$this->assertCount( count( $data['elements'] ), $url_metric->elements );
+		for ( $i = 0, $length = count( $data['elements'] ); $i < $length; $i++ ) {
+			$this->assertSame( (bool) $data['elements'][ $i ]['isLCP'], $url_metric->elements[ $i ]['isLCP'] );
+			$this->assertSame( (bool) $data['elements'][ $i ]['isLCPCandidate'], $url_metric->elements[ $i ]['isLCPCandidate'] );
+			$this->assertSame( (float) $data['elements'][ $i ]['intersectionRatio'], $url_metric->elements[ $i ]['intersectionRatio'] );
+			$this->assertSame( array_map( 'floatval', $data['elements'][ $i ]['boundingClientRect'] ), $url_metric->elements[ $i ]['boundingClientRect'] );
+			$this->assertSame( array_map( 'floatval', $data['elements'][ $i ]['intersectionRect'] ), $url_metric->elements[ $i ]['intersectionRect'] );
+		}
+		$this->assertSame( $url_metric->elements, $url_metric->get_elements() );
+		$this->assertSame( $url_metric->elements, $url_metric->get( 'elements' ) );
 
 		$this->assertSame( $data['url'], $url_metric->get_url() );
 		$this->assertSame( $data['url'], $url_metric->get( 'url' ) );
@@ -225,6 +252,8 @@ public function test_constructor( array $data, string $error = '' ): void {
 			$this->assertTrue( wp_is_uuid( $serialized['uuid'] ) );
 			unset( $serialized['uuid'] );
 		}
+
+		// The use of assertEquals instead of assertSame ensures that lossy type comparisons are employed.
 		$this->assertEquals( $data, $serialized );
 	}
 

From 00d57b46c4a1a5105d3a0f5ca5bc30b46df15705 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Fri, 6 Sep 2024 18:14:47 -0700
Subject: [PATCH 09/16] Persist unknown properties in stored URL Metrics but
 reject in new URL Metric storage requests

---
 .../class-od-strict-url-metric.php            |  63 ++++++
 .../class-od-url-metric.php                   |  17 +-
 plugins/optimization-detective/load.php       |   1 +
 .../storage/rest-api.php                      |  30 +--
 .../test-class-od-url-metrics-post-type.php   |  17 +-
 .../tests/storage/test-rest-api.php           |  60 +++++-
 .../tests/test-class-od-strict-url-metric.php |  62 ++++++
 .../tests/test-class-od-url-metric.php        | 183 +++++++++++++++++-
 8 files changed, 402 insertions(+), 31 deletions(-)
 create mode 100644 plugins/optimization-detective/class-od-strict-url-metric.php
 create mode 100644 plugins/optimization-detective/tests/test-class-od-strict-url-metric.php

diff --git a/plugins/optimization-detective/class-od-strict-url-metric.php b/plugins/optimization-detective/class-od-strict-url-metric.php
new file mode 100644
index 0000000000..89d1196435
--- /dev/null
+++ b/plugins/optimization-detective/class-od-strict-url-metric.php
@@ -0,0 +1,63 @@
+<?php
+/**
+ * Optimization Detective: OD_Strict_URL_Metric class
+ *
+ * @package optimization-detective
+ * @since n.e.x.t
+ */
+
+// Exit if accessed directly.
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+/**
+ * Representation of the measurements taken from a single client's visit to a specific URL without additionalProperties allowed.
+ *
+ * This is used exclusively in the REST API endpoint for capturing new URL metrics to prevent invalid additional data from being
+ * submitted in the request. For URL metrics which have been stored the looser OD_URL_Metric class is used instead.
+ *
+ * @since n.e.x.t
+ * @access private
+ */
+final class OD_Strict_URL_Metric extends OD_URL_Metric {
+
+	/**
+	 * Gets JSON schema for URL Metric without additionalProperties.
+	 *
+	 * @since n.e.x.t
+	 *
+	 * @return array<string, mixed> Schema.
+	 */
+	public static function get_json_schema(): array {
+		return self::falsify_additional_properties( parent::get_json_schema() );
+	}
+
+	/**
+	 * Recursively processes the schema to ensure that all objects have additionalProperties set to false.
+	 *
+	 * @since n.e.x.t
+	 *
+	 * @param mixed $schema Schema.
+	 * @return mixed Processed schema.
+	 */
+	private static function falsify_additional_properties( $schema ) {
+		if ( ! isset( $schema['type'] ) ) {
+			return $schema;
+		}
+		if ( 'object' === $schema['type'] ) {
+			$schema['additionalProperties'] = false;
+			if ( isset( $schema['properties'] ) && is_array( $schema['properties'] ) ) {
+				$schema['properties'] = array_map(
+					static function ( $property_schema ) {
+						return self::falsify_additional_properties( $property_schema );
+					},
+					$schema['properties']
+				);
+			}
+		} elseif ( 'array' === $schema['type'] && isset( $schema['items'] ) && is_array( $schema['items'] ) ) {
+			$schema['items'] = self::falsify_additional_properties( $schema['items'] );
+		}
+		return $schema;
+	}
+}
diff --git a/plugins/optimization-detective/class-od-url-metric.php b/plugins/optimization-detective/class-od-url-metric.php
index 44ea0b513c..9017322f57 100644
--- a/plugins/optimization-detective/class-od-url-metric.php
+++ b/plugins/optimization-detective/class-od-url-metric.php
@@ -53,14 +53,14 @@
  * @since 0.1.0
  * @access private
  */
-final class OD_URL_Metric implements JsonSerializable {
+class OD_URL_Metric implements JsonSerializable {
 
 	/**
 	 * Data.
 	 *
 	 * @var Data
 	 */
-	private $data;
+	protected $data;
 
 	/**
 	 * Constructor.
@@ -123,7 +123,7 @@ private function prepare_data( array $data ): array {
 	 */
 	public static function get_json_schema(): array {
 		/*
-		 * The intersectionRect and clientBoundingRect are both instances of the DOMRectReadOnly, which
+		 * The intersectionRect and boundingClientRect are both instances of the DOMRectReadOnly, which
 		 * the following schema describes. See <https://developer.mozilla.org/en-US/docs/Web/API/DOMRectReadOnly>.
 		 * Note that 'number' is used specifically instead of 'integer' because the values are all specified as
 		 * floats/doubles.
@@ -232,11 +232,18 @@ public static function get_json_schema(): array {
 							'intersectionRect'   => $dom_rect_schema,
 							'boundingClientRect' => $dom_rect_schema,
 						),
-						'additionalProperties' => false,
+
+						// Additional properties may be added to the schema for items of elements via the od_url_metric_schema_element_item_additional_properties filter.
+						// See further explanation below.
+						'additionalProperties' => true,
 					),
 				),
 			),
-			'additionalProperties' => false,
+			// Additional root properties may be added to the schema via the od_url_metric_schema_root_additional_properties filter.
+			// Therefore, additionalProperties is set to true so that additional properties defined in the extended schema may persist
+			// in a stored URL Metric even when the extension is deactivated. For REST API requests, the OD_Strict_URL_Metric
+			// which sets this to false so that newly-submitted URL Metrics only ever include the known properties.
+			'additionalProperties' => true,
 		);
 
 		/**
diff --git a/plugins/optimization-detective/load.php b/plugins/optimization-detective/load.php
index 59e5405e7f..52902fb31f 100644
--- a/plugins/optimization-detective/load.php
+++ b/plugins/optimization-detective/load.php
@@ -99,6 +99,7 @@ static function ( string $version ): void {
 		require_once __DIR__ . '/class-od-data-validation-exception.php';
 		require_once __DIR__ . '/class-od-html-tag-processor.php';
 		require_once __DIR__ . '/class-od-url-metric.php';
+		require_once __DIR__ . '/class-od-strict-url-metric.php';
 		require_once __DIR__ . '/class-od-url-metrics-group.php';
 		require_once __DIR__ . '/class-od-url-metrics-group-collection.php';
 
diff --git a/plugins/optimization-detective/storage/rest-api.php b/plugins/optimization-detective/storage/rest-api.php
index 17a2e4fc1d..77b7fda2d0 100644
--- a/plugins/optimization-detective/storage/rest-api.php
+++ b/plugins/optimization-detective/storage/rest-api.php
@@ -67,7 +67,7 @@ function od_register_endpoint(): void {
 			'methods'             => 'POST',
 			'args'                => array_merge(
 				$args,
-				rest_get_endpoint_args_for_schema( OD_URL_Metric::get_json_schema() )
+				rest_get_endpoint_args_for_schema( OD_Strict_URL_Metric::get_json_schema() )
 			),
 			'callback'            => static function ( WP_REST_Request $request ) {
 				return od_handle_rest_request( $request );
@@ -128,19 +128,23 @@ function od_handle_rest_request( WP_REST_Request $request ) {
 	OD_Storage_Lock::set_lock();
 
 	try {
-		$url_metric = new OD_URL_Metric(
-			array_merge(
-				wp_array_slice_assoc(
-					$request->get_params(),
-					array_keys( OD_URL_Metric::get_json_schema()['properties'] )
-				),
-				array(
-					// Now supply the readonly args which were omitted from the REST API params due to being `readonly`.
-					'timestamp' => microtime( true ),
-					'uuid'      => wp_generate_uuid4(),
-				)
+		$data = $request->get_params();
+		// Remove params which are only used for the REST API request and which are not part of a URL Metric.
+		unset(
+			$data['slug'],
+			$data['nonce']
+		);
+		$data = array_merge(
+			$data,
+			array(
+				// Now supply the readonly args which were omitted from the REST API params due to being `readonly`.
+				'timestamp' => microtime( true ),
+				'uuid'      => wp_generate_uuid4(),
 			)
 		);
+
+		// The "strict" URL Metric class is being used here to ensure additionalProperties of all objects are disallowed.
+		$url_metric = new OD_Strict_URL_Metric( $data );
 	} catch ( OD_Data_Validation_Exception $e ) {
 		return new WP_Error(
 			'rest_invalid_param',
@@ -174,7 +178,7 @@ function od_handle_rest_request( WP_REST_Request $request ) {
 	 *
 	 *     @var int                                   $post_id
 	 *     @var WP_REST_Request<array<string, mixed>> $request
-	 *     @var OD_URL_Metric                         $url_metric
+	 *     @var OD_Strict_URL_Metric                  $url_metric
 	 *     @var OD_URL_Metrics_Group                  $group
 	 *     @var OD_URL_Metrics_Group_Collection       $group_collection
 	 * }
diff --git a/plugins/optimization-detective/tests/storage/test-class-od-url-metrics-post-type.php b/plugins/optimization-detective/tests/storage/test-class-od-url-metrics-post-type.php
index 135595194c..b9eec5d906 100644
--- a/plugins/optimization-detective/tests/storage/test-class-od-url-metrics-post-type.php
+++ b/plugins/optimization-detective/tests/storage/test-class-od-url-metrics-post-type.php
@@ -102,27 +102,34 @@ public function data_provider_test_get_url_metrics_from_post(): array {
 		$valid_content_with_uuid            = $valid_content;
 		$valid_content_with_uuid[0]['uuid'] = wp_generate_uuid4();
 
+		$valid_content_with_extra_property             = $valid_content_with_uuid;
+		$valid_content_with_extra_property[0]['extra'] = 'foo';
+
 		return array(
-			'malformed_json'  => array(
+			'malformed_json'        => array(
 				'post_content'   => '{"bad":',
 				'expected_value' => array(),
 			),
-			'not_array_json'  => array(
+			'not_array_json'        => array(
 				'post_content'   => '{"cool":"beans"}',
 				'expected_value' => array(),
 			),
-			'missing_keys'    => array(
+			'missing_keys'          => array(
 				'post_content'   => '[{},{},{}]',
 				'expected_value' => array(),
 			),
-			'valid_sans_uuid' => array(
+			'valid_sans_uuid'       => array(
 				'post_content'   => wp_json_encode( $valid_content ),
 				'expected_value' => $valid_content,
 			),
-			'valid_with_uuid' => array(
+			'valid_with_uuid'       => array(
 				'post_content'   => wp_json_encode( $valid_content_with_uuid ),
 				'expected_value' => $valid_content_with_uuid,
 			),
+			'valid_with_extra_prop' => array(
+				'post_content'   => wp_json_encode( $valid_content_with_extra_property ),
+				'expected_value' => $valid_content_with_extra_property,
+			),
 		);
 	}
 
diff --git a/plugins/optimization-detective/tests/storage/test-rest-api.php b/plugins/optimization-detective/tests/storage/test-rest-api.php
index 5661a469bc..603d40cd98 100644
--- a/plugins/optimization-detective/tests/storage/test-rest-api.php
+++ b/plugins/optimization-detective/tests/storage/test-rest-api.php
@@ -22,15 +22,49 @@ public function test_od_register_endpoint_hooked(): void {
 		$this->assertSame( 10, has_action( 'rest_api_init', 'od_register_endpoint' ) );
 	}
 
+	/**
+	 * Data provider.
+	 *
+	 * @return array<string, mixed>
+	 */
+	public function data_provider_to_test_rest_request_good_params(): array {
+		return array(
+			'not_extended' => array(
+				'set_up' => function () {
+					return $this->get_valid_params();
+				},
+			),
+			'extended'     => array(
+				'set_up' => function () {
+					add_filter(
+						'od_url_metric_schema_root_additional_properties',
+						static function ( array $properties ): array {
+							$properties['extra'] = array(
+								'type' => 'string',
+							);
+							return $properties;
+						}
+					);
+
+					$params = $this->get_valid_params();
+					$params['extra'] = 'foo';
+					return $params;
+				},
+			),
+		);
+	}
+
 	/**
 	 * Test good params.
 	 *
+	 * @dataProvider data_provider_to_test_rest_request_good_params
+	 *
 	 * @covers ::od_register_endpoint
 	 * @covers ::od_handle_rest_request
 	 */
-	public function test_rest_request_good_params(): void {
+	public function test_rest_request_good_params( Closure $set_up ): void {
+		$valid_params = $set_up();
 		$request      = new WP_REST_Request( 'POST', self::ROUTE );
-		$valid_params = $this->get_valid_params();
 		$this->assertCount( 0, get_posts( array( 'post_type' => OD_URL_Metrics_Post_Type::SLUG ) ) );
 		$request->set_body_params( $valid_params );
 		$response = rest_get_server()->dispatch( $request );
@@ -47,6 +81,13 @@ public function test_rest_request_good_params(): void {
 		$this->assertCount( 1, $url_metrics, 'Expected number of URL metrics stored.' );
 		$this->assertSame( $valid_params['elements'], $url_metrics[0]->get_elements() );
 		$this->assertSame( $valid_params['viewport']['width'], $url_metrics[0]->get_viewport_width() );
+
+		$expected_data = $valid_params;
+		unset( $expected_data['nonce'], $expected_data['slug'] );
+		$this->assertSame(
+			$expected_data,
+			wp_array_slice_assoc( $url_metrics[0]->jsonSerialize(), array_keys( $expected_data ) )
+		);
 	}
 
 	/**
@@ -151,6 +192,19 @@ function ( $params ) {
 						),
 					),
 				),
+				'invalid_root_property'                    => array(
+					'is_touch' => false,
+				),
+				'invalid_element_property'                 => array(
+					'elements' => array(
+						array_merge(
+							$valid_element,
+							array(
+								'is_big' => true,
+							)
+						),
+					),
+				),
 			)
 		);
 	}
@@ -406,6 +460,7 @@ private function get_valid_params( array $extras = array() ): array {
 				),
 			)
 		)->jsonSerialize();
+		unset( $data['timestamp'], $data['uuid'] ); // Since these are readonly.
 		$data = array_merge(
 			array(
 				'slug'  => $slug,
@@ -413,7 +468,6 @@ private function get_valid_params( array $extras = array() ): array {
 			),
 			$data
 		);
-		unset( $data['timestamp'] ); // Since provided by default args.
 		if ( count( $extras ) > 0 ) {
 			$data = $this->recursive_merge( $data, $extras );
 		}
diff --git a/plugins/optimization-detective/tests/test-class-od-strict-url-metric.php b/plugins/optimization-detective/tests/test-class-od-strict-url-metric.php
new file mode 100644
index 0000000000..33be2b8ffc
--- /dev/null
+++ b/plugins/optimization-detective/tests/test-class-od-strict-url-metric.php
@@ -0,0 +1,62 @@
+<?php
+/**
+ * Tests for optimization-detective class OD_Strict_URL_Metric.
+ *
+ * @package optimization-detective
+ *
+ * @coversDefaultClass OD_Strict_URL_Metric
+ */
+class Test_OD_Strict_URL_Metric extends WP_UnitTestCase {
+	use Optimization_Detective_Test_Helpers;
+
+	/**
+	 * Tests get_json_schema().
+	 *
+	 * @covers ::get_json_schema
+	 */
+	public function test_get_json_schema(): void {
+		add_filter(
+			'od_url_metric_schema_root_additional_properties',
+			static function ( array $properties ) {
+				$properties['colors'] = array(
+					'type'                 => 'object',
+					'properties'           => array(
+						'hex' => array(
+							'type' => 'string',
+						),
+					),
+					'additionalProperties' => true,
+				);
+				return $properties;
+			}
+		);
+		add_filter(
+			'od_url_metric_schema_element_item_additional_properties',
+			static function ( array $properties ) {
+				$properties['region'] = array(
+					'type'                 => 'object',
+					'properties'           => array(
+						'continent' => array(
+							'type' => 'string',
+						),
+					),
+					'additionalProperties' => true,
+				);
+				return $properties;
+			}
+		);
+		$loose_schema = OD_URL_Metric::get_json_schema();
+		$this->assertTrue( $loose_schema['additionalProperties'] );
+		$this->assertFalse( $loose_schema['properties']['viewport']['additionalProperties'] ); // The viewport is never extensible. Only the root and the elements are.
+		$this->assertTrue( $loose_schema['properties']['elements']['items']['additionalProperties'] );
+		$this->assertTrue( $loose_schema['properties']['elements']['items']['properties']['region']['additionalProperties'] );
+		$this->assertTrue( $loose_schema['properties']['colors']['additionalProperties'] );
+
+		$strict_schema = OD_Strict_URL_Metric::get_json_schema();
+		$this->assertFalse( $strict_schema['additionalProperties'] );
+		$this->assertFalse( $strict_schema['properties']['viewport']['additionalProperties'] );
+		$this->assertFalse( $strict_schema['properties']['elements']['items']['additionalProperties'] );
+		$this->assertFalse( $strict_schema['properties']['elements']['items']['properties']['region']['additionalProperties'] );
+		$this->assertFalse( $strict_schema['properties']['colors']['additionalProperties'] );
+	}
+}
diff --git a/plugins/optimization-detective/tests/test-class-od-url-metric.php b/plugins/optimization-detective/tests/test-class-od-url-metric.php
index 96a34baa2b..b678bdbf8e 100644
--- a/plugins/optimization-detective/tests/test-class-od-url-metric.php
+++ b/plugins/optimization-detective/tests/test-class-od-url-metric.php
@@ -14,7 +14,7 @@ class Test_OD_URL_Metric extends WP_UnitTestCase {
 	 *
 	 * @return array<string, mixed> Data.
 	 */
-	public function data_provider(): array {
+	public function data_provider_to_test_constructor(): array {
 		$viewport      = array(
 			'width'  => 640,
 			'height' => 480,
@@ -198,15 +198,15 @@ static function ( $value ) {
 	/**
 	 * Tests construction.
 	 *
-	 * @todo PHPStan complains when adding @covers tags for `::get()` and `::__get()` saying they are invalid method references.
-	 *
 	 * @covers ::get_viewport
 	 * @covers ::get_viewport_width
 	 * @covers ::get_timestamp
 	 * @covers ::get_elements
 	 * @covers ::jsonSerialize
+	 * @covers ::get
+	 * @covers ::__get
 	 *
-	 * @dataProvider data_provider
+	 * @dataProvider data_provider_to_test_constructor
 	 *
 	 * @param array<string, mixed> $data  Data.
 	 * @param string               $error Error.
@@ -257,6 +257,175 @@ public function test_constructor( array $data, string $error = '' ): void {
 		$this->assertEquals( $data, $serialized );
 	}
 
+	/**
+	 * Data provider.
+	 *
+	 * @return array<string, mixed> Data.
+	 */
+	public function data_provider_to_test_constructor_with_extended_schema(): array {
+		$viewport      = array(
+			'width'  => 640,
+			'height' => 480,
+		);
+		$valid_element = array(
+			'isLCP'              => true,
+			'isLCPCandidate'     => true,
+			'xpath'              => '/*[0][self::HTML]/*[1][self::BODY]/*[0][self::IMG]',
+			'intersectionRatio'  => 1.0,
+			'intersectionRect'   => $this->get_sample_dom_rect(),
+			'boundingClientRect' => $this->get_sample_dom_rect(),
+		);
+
+		return array(
+			'added_valid_root_property'      => array(
+				'set_up' => static function (): void {
+					add_filter(
+						'od_url_metric_schema_root_additional_properties',
+						static function ( array $properties ): array {
+							$properties['isTouch'] = array(
+								'type' => 'boolean',
+							);
+							return $properties;
+						}
+					);
+				},
+				'data'   => array(
+					'url'       => home_url( '/' ),
+					'viewport'  => $viewport,
+					'timestamp' => microtime( true ),
+					'elements'  => array(),
+					'isTouch'   => 1, // This should get cast to `true` after the extended schema has applied.
+				),
+				'assert' => function ( OD_URL_Metric $extended_url_metric, OD_URL_Metric $original_url_metric ): void {
+					$this->assertSame( $original_url_metric->get_viewport(), $extended_url_metric->get_viewport() );
+
+					$original_data = $original_url_metric->jsonSerialize();
+					$this->assertArrayHasKey( 'isTouch', $original_data );
+					$this->assertSame( 1, $original_data['isTouch'] );
+					$this->assertSame( 1, $original_url_metric->get( 'isTouch' ) );
+
+					$extended_data = $extended_url_metric->jsonSerialize();
+					$this->assertArrayHasKey( 'isTouch', $extended_data );
+					$this->assertTrue( $extended_data['isTouch'] );
+					$this->assertTrue( $extended_url_metric->get( 'isTouch' ) );
+				},
+			),
+
+			'added_invalid_root_property'    => array(
+				'set_up' => static function (): void {
+					add_filter(
+						'od_url_metric_schema_root_additional_properties',
+						static function ( array $properties ): array {
+							$properties['isTouch'] = array(
+								'type' => 'boolean',
+							);
+							return $properties;
+						}
+					);
+				},
+				'data'   => array(
+					'url'       => home_url( '/' ),
+					'viewport'  => $viewport,
+					'timestamp' => microtime( true ),
+					'elements'  => array(),
+					'isTouch'   => array( 'cannot be cast to boolean' ),
+				),
+				'assert' => static function (): void {},
+				'error'  => 'OD_URL_Metric[isTouch] is not of type boolean.',
+			),
+
+			'added_valid_element_property'   => array(
+				'set_up' => static function (): void {
+					add_filter(
+						'od_url_metric_schema_element_item_additional_properties',
+						static function ( array $properties ): array {
+							$properties['isColorful'] = array(
+								'type' => 'boolean',
+							);
+							return $properties;
+						}
+					);
+				},
+				'data'   => array(
+					'url'       => home_url( '/' ),
+					'viewport'  => $viewport,
+					'timestamp' => microtime( true ),
+					'elements'  => array(
+						array_merge(
+							$valid_element,
+							array( 'isColorful' => 'false' )
+						),
+					),
+				),
+				'assert' => function ( OD_URL_Metric $extended_url_metric, OD_URL_Metric $original_url_metric ): void {
+					$this->assertSame( $original_url_metric->get_viewport(), $extended_url_metric->get_viewport() );
+
+					$original_data = $original_url_metric->jsonSerialize();
+					$this->assertArrayHasKey( 'isColorful', $original_data['elements'][0] );
+					$this->assertSame( 'false', $original_data['elements'][0]['isColorful'] );
+					$this->assertSame( 'false', $original_url_metric->get_elements()[0]['isColorful'] );
+
+					$extended_data = $extended_url_metric->jsonSerialize();
+					$this->assertArrayHasKey( 'isColorful', $extended_data['elements'][0] );
+					$this->assertFalse( $extended_data['elements'][0]['isColorful'] );
+					$this->assertFalse( $extended_url_metric->get_elements()[0]['isColorful'] );
+				},
+			),
+
+			'added_invalid_element_property' => array(
+				'set_up' => static function (): void {
+					add_filter(
+						'od_url_metric_schema_element_item_additional_properties',
+						static function ( array $properties ): array {
+							$properties['isColorful'] = array(
+								'type' => 'boolean',
+							);
+							return $properties;
+						}
+					);
+				},
+				'data'   => array(
+					'url'       => home_url( '/' ),
+					'viewport'  => $viewport,
+					'timestamp' => microtime( true ),
+					'elements'  => array(
+						array_merge(
+							$valid_element,
+							array( 'isColorful' => array( 'cannot be cast to boolean' ) )
+						),
+					),
+				),
+				'assert' => static function (): void {},
+				'error'  => 'OD_URL_Metric[elements][0][isColorful] is not of type boolean.',
+			),
+		);
+	}
+
+	/**
+	 * Tests construction with extended schema.
+	 *
+	 * @covers ::jsonSerialize
+	 * @covers ::get
+	 * @covers ::__get
+	 *
+	 * @dataProvider data_provider_to_test_constructor_with_extended_schema
+	 *
+	 * @param Closure              $set_up Set up to extend schema.
+	 * @param array<string, mixed> $data   Data.
+	 * @param Closure              $assert Assert.
+	 * @param string               $error  Error.
+	 */
+	public function test_constructor_with_extended_schema( Closure $set_up, array $data, Closure $assert, string $error = '' ): void {
+		if ( '' !== $error ) {
+			$this->expectException( OD_Data_Validation_Exception::class );
+			$this->expectExceptionMessage( $error );
+		}
+		$url_metric_sans_extended_schema = new OD_URL_Metric( $data );
+		$set_up();
+		$url_metric_with_extended_schema = new OD_URL_Metric( $data );
+		$assert( $url_metric_with_extended_schema, $url_metric_sans_extended_schema );
+	}
+
 	/**
 	 * Tests get_json_schema().
 	 *
@@ -463,7 +632,11 @@ protected function check_schema_subset( array $schema, string $path, bool $exten
 		if ( 'object' === $schema['type'] ) {
 			$this->assertArrayHasKey( 'properties', $schema, $path );
 			$this->assertArrayHasKey( 'additionalProperties', $schema, $path );
-			$this->assertFalse( $schema['additionalProperties'] );
+			if ( 'root/viewport' === $path || 'root/elements/items/intersectionRect' === $path || 'root/elements/items/boundingClientRect' === $path ) {
+				$this->assertFalse( $schema['additionalProperties'], "Path: $path" );
+			} else {
+				$this->assertTrue( $schema['additionalProperties'], "Path: $path" );
+			}
 			foreach ( $schema['properties'] as $key => $property_schema ) {
 				$this->check_schema_subset( $property_schema, "$path/$key", $extended );
 			}

From 22711e42308b47cba5f61f1f51fb89dd89e8f889 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Tue, 10 Sep 2024 09:58:02 -0700
Subject: [PATCH 10/16] Add return description

Co-authored-by: Felix Arntz <felixarntz@google.com>
---
 plugins/optimization-detective/class-od-url-metric.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/plugins/optimization-detective/class-od-url-metric.php b/plugins/optimization-detective/class-od-url-metric.php
index 9017322f57..781c4cb0a1 100644
--- a/plugins/optimization-detective/class-od-url-metric.php
+++ b/plugins/optimization-detective/class-od-url-metric.php
@@ -348,7 +348,7 @@ protected static function extend_schema_with_optional_properties( array $propert
 	 * @todo Instead of returning null when the key doesn't exist, should the `default` value be returned as defined in the schema?
 	 *
 	 * @param string $key Property.
-	 * @return mixed|null
+	 * @return mixed|null The property value, or null if not set.
 	 */
 	public function get( string $key ) {
 		return $this->data[ $key ] ?? null;

From 384fa53f9de60b3080b515ab95a06070b50b1a04 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Tue, 10 Sep 2024 11:31:00 -0700
Subject: [PATCH 11/16] Use properties instead of get methods

---
 .../class-od-url-metrics-group-collection.php               | 4 ++--
 .../optimization-detective/class-od-url-metrics-group.php   | 6 +++---
 .../storage/class-od-url-metrics-post-type.php              | 4 ++--
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/plugins/optimization-detective/class-od-url-metrics-group-collection.php b/plugins/optimization-detective/class-od-url-metrics-group-collection.php
index 21bce9a0c5..dd2306a73b 100644
--- a/plugins/optimization-detective/class-od-url-metrics-group-collection.php
+++ b/plugins/optimization-detective/class-od-url-metrics-group-collection.php
@@ -193,7 +193,7 @@ private function create_groups(): array {
 	 */
 	public function add_url_metric( OD_URL_Metric $new_url_metric ): void {
 		foreach ( $this->groups as $group ) {
-			if ( $group->is_viewport_width_in_range( $new_url_metric->get_viewport_width() ) ) {
+			if ( $group->is_viewport_width_in_range( $new_url_metric->viewport['width'] ) ) {
 				$group->add_url_metric( $new_url_metric );
 				return;
 			}
@@ -416,7 +416,7 @@ public function get_all_element_max_intersection_ratios(): array {
 			 */
 			foreach ( $this->groups as $group ) {
 				foreach ( $group as $url_metric ) {
-					foreach ( $url_metric->get_elements() as $element ) {
+					foreach ( $url_metric->elements as $element ) {
 						$element_max_intersection_ratios[ $element['xpath'] ] = array_key_exists( $element['xpath'], $element_max_intersection_ratios )
 							? max( $element_max_intersection_ratios[ $element['xpath'] ], $element['intersectionRatio'] )
 							: $element['intersectionRatio'];
diff --git a/plugins/optimization-detective/class-od-url-metrics-group.php b/plugins/optimization-detective/class-od-url-metrics-group.php
index 97e1bf7cc7..79dd57cf61 100644
--- a/plugins/optimization-detective/class-od-url-metrics-group.php
+++ b/plugins/optimization-detective/class-od-url-metrics-group.php
@@ -181,7 +181,7 @@ public function is_viewport_width_in_range( int $viewport_width ): bool {
 	 * @param OD_URL_Metric $url_metric URL metric.
 	 */
 	public function add_url_metric( OD_URL_Metric $url_metric ): void {
-		if ( ! $this->is_viewport_width_in_range( $url_metric->get_viewport_width() ) ) {
+		if ( ! $this->is_viewport_width_in_range( $url_metric->viewport['width'] ) ) {
 			throw new InvalidArgumentException(
 				esc_html__( 'URL metric is not in the viewport range for group.', 'optimization-detective' )
 			);
@@ -201,7 +201,7 @@ public function add_url_metric( OD_URL_Metric $url_metric ): void {
 			usort(
 				$this->url_metrics,
 				static function ( OD_URL_Metric $a, OD_URL_Metric $b ): int {
-					return $b->get_timestamp() <=> $a->get_timestamp();
+					return $b->timestamp <=> $a->timestamp;
 				}
 			);
 
@@ -283,7 +283,7 @@ public function get_lcp_element(): ?array {
 			$breadcrumb_element = array();
 
 			foreach ( $this->url_metrics as $url_metric ) {
-				foreach ( $url_metric->get_elements() as $element ) {
+				foreach ( $url_metric->elements as $element ) {
 					if ( ! $element['isLCP'] ) {
 						continue;
 					}
diff --git a/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php b/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
index 43079459a1..8bfcccd096 100644
--- a/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
+++ b/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
@@ -200,7 +200,7 @@ public static function store_url_metric( string $slug, OD_URL_Metric $new_url_me
 			// multiple URL Metric instances, each of which also contains the URL for which the metric was captured. The URL
 			// appearing in the post title is therefore the most recent URL seen for the URL Metrics which have the same
 			// normalized query vars among them.
-			'post_title' => $new_url_metric->get_url(),
+			'post_title' => $new_url_metric->url,
 		);
 
 		$post = self::get_post( $slug );
@@ -221,7 +221,7 @@ public static function store_url_metric( string $slug, OD_URL_Metric $new_url_me
 		);
 
 		try {
-			$group = $group_collection->get_group_for_viewport_width( $new_url_metric->get_viewport_width() );
+			$group = $group_collection->get_group_for_viewport_width( $new_url_metric->viewport['width'] );
 			$group->add_url_metric( $new_url_metric );
 		} catch ( InvalidArgumentException $e ) {
 			return new WP_Error( 'invalid_url_metric', $e->getMessage() );

From ed5815158552d27359a730e1f6dfa41ccbcc61c9 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Tue, 10 Sep 2024 11:36:31 -0700
Subject: [PATCH 12/16] Replace remaining use of get_timestamp

---
 plugins/optimization-detective/class-od-url-metrics-group.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/plugins/optimization-detective/class-od-url-metrics-group.php b/plugins/optimization-detective/class-od-url-metrics-group.php
index 79dd57cf61..6eb364aa19 100644
--- a/plugins/optimization-detective/class-od-url-metrics-group.php
+++ b/plugins/optimization-detective/class-od-url-metrics-group.php
@@ -229,7 +229,7 @@ public function is_complete(): bool {
 			}
 			$current_time = microtime( true );
 			foreach ( $this->url_metrics as $url_metric ) {
-				if ( $current_time > $url_metric->get_timestamp() + $this->freshness_ttl ) {
+				if ( $current_time > $url_metric->timestamp + $this->freshness_ttl ) {
 					return false;
 				}
 			}

From aa1e66334e52abb2e9e0acb168c080346abcc907 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Tue, 10 Sep 2024 13:51:30 -0700
Subject: [PATCH 13/16] Disallow default value for schema

---
 .../class-od-url-metric.php                   | 16 +++-
 .../tests/test-class-od-url-metric.php        | 96 +++++++++++++++++--
 2 files changed, 103 insertions(+), 9 deletions(-)

diff --git a/plugins/optimization-detective/class-od-url-metric.php b/plugins/optimization-detective/class-od-url-metric.php
index 781c4cb0a1..261423b776 100644
--- a/plugins/optimization-detective/class-od-url-metric.php
+++ b/plugins/optimization-detective/class-od-url-metric.php
@@ -321,12 +321,11 @@ protected static function extend_schema_with_optional_properties( array $propert
 				);
 				continue;
 			}
-			// TODO: Should 'default' be required?
 			if ( isset( $property_schema['required'] ) && false !== $property_schema['required'] ) {
 				$doing_it_wrong(
 					sprintf(
 						/* translators: 1: property name, 2: 'required' */
-						__( 'Supplied schema property "%1$s" has a truthy value for "%2$s". All extended properties must be optional so that URL Metrics are not all immediately invalidated once an extension is deactivated..', 'optimization-detective' ),
+						__( 'Supplied schema property "%1$s" has a truthy value for "%2$s". All extended properties must be optional so that URL Metrics are not all immediately invalidated once an extension is deactivated.', 'optimization-detective' ),
 						$property_key,
 						'required'
 					)
@@ -334,6 +333,18 @@ protected static function extend_schema_with_optional_properties( array $propert
 			}
 			$property_schema['required'] = false;
 
+			if ( isset( $property_schema['default'] ) ) {
+				$doing_it_wrong(
+					sprintf(
+						/* translators: 1: property name, 2: 'default' */
+						__( 'Supplied schema property "%1$s" has disallowed "%2$s" specified.', 'optimization-detective' ),
+						$property_key,
+						'default'
+					)
+				);
+				unset( $property_schema['default'] );
+			}
+
 			$properties_schema[ $property_key ] = $property_schema;
 		}
 		return $properties_schema;
@@ -345,7 +356,6 @@ protected static function extend_schema_with_optional_properties( array $propert
 	 * This is particularly useful in conjunction with the `od_url_metric_schema_root_additional_properties` filter.
 	 *
 	 * @since n.e.x.t
-	 * @todo Instead of returning null when the key doesn't exist, should the `default` value be returned as defined in the schema?
 	 *
 	 * @param string $key Property.
 	 * @return mixed|null The property value, or null if not set.
diff --git a/plugins/optimization-detective/tests/test-class-od-url-metric.php b/plugins/optimization-detective/tests/test-class-od-url-metric.php
index b678bdbf8e..b3732b6ae7 100644
--- a/plugins/optimization-detective/tests/test-class-od-url-metric.php
+++ b/plugins/optimization-detective/tests/test-class-od-url-metric.php
@@ -277,7 +277,7 @@ public function data_provider_to_test_constructor_with_extended_schema(): array
 		);
 
 		return array(
-			'added_valid_root_property'      => array(
+			'added_valid_root_property_populated'        => array(
 				'set_up' => static function (): void {
 					add_filter(
 						'od_url_metric_schema_root_additional_properties',
@@ -311,7 +311,38 @@ static function ( array $properties ): array {
 				},
 			),
 
-			'added_invalid_root_property'    => array(
+			'added_valid_root_property_not_populated'    => array(
+				'set_up' => static function (): void {
+					add_filter(
+						'od_url_metric_schema_root_additional_properties',
+						static function ( array $properties ): array {
+							$properties['isTouch'] = array(
+								'type' => 'boolean',
+							);
+							return $properties;
+						}
+					);
+				},
+				'data'   => array(
+					'url'       => home_url( '/' ),
+					'viewport'  => $viewport,
+					'timestamp' => microtime( true ),
+					'elements'  => array(),
+				),
+				'assert' => function ( OD_URL_Metric $extended_url_metric, OD_URL_Metric $original_url_metric ): void {
+					$this->assertSame( $original_url_metric->get_viewport(), $extended_url_metric->get_viewport() );
+
+					$original_data = $original_url_metric->jsonSerialize();
+					$this->assertArrayNotHasKey( 'isTouch', $original_data );
+					$this->assertNull( $original_url_metric->get( 'isTouch' ) );
+
+					$extended_data = $extended_url_metric->jsonSerialize();
+					$this->assertArrayNotHasKey( 'isTouch', $extended_data ); // If rest_sanitize_value_from_schema() took default into account (and we allowed defaults), this could be different.
+					$this->assertNull( $extended_url_metric->get( 'isTouch' ) );
+				},
+			),
+
+			'added_invalid_root_property'                => array(
 				'set_up' => static function (): void {
 					add_filter(
 						'od_url_metric_schema_root_additional_properties',
@@ -334,7 +365,7 @@ static function ( array $properties ): array {
 				'error'  => 'OD_URL_Metric[isTouch] is not of type boolean.',
 			),
 
-			'added_valid_element_property'   => array(
+			'added_valid_element_property_populated'     => array(
 				'set_up' => static function (): void {
 					add_filter(
 						'od_url_metric_schema_element_item_additional_properties',
@@ -363,16 +394,45 @@ static function ( array $properties ): array {
 					$original_data = $original_url_metric->jsonSerialize();
 					$this->assertArrayHasKey( 'isColorful', $original_data['elements'][0] );
 					$this->assertSame( 'false', $original_data['elements'][0]['isColorful'] );
-					$this->assertSame( 'false', $original_url_metric->get_elements()[0]['isColorful'] );
+					$this->assertSame( 'false', $original_url_metric->elements[0]['isColorful'] );
 
 					$extended_data = $extended_url_metric->jsonSerialize();
 					$this->assertArrayHasKey( 'isColorful', $extended_data['elements'][0] );
 					$this->assertFalse( $extended_data['elements'][0]['isColorful'] );
-					$this->assertFalse( $extended_url_metric->get_elements()[0]['isColorful'] );
+					$this->assertFalse( $extended_url_metric->elements[0]['isColorful'] );
+				},
+			),
+
+			'added_valid_element_property_not_populated' => array(
+				'set_up' => static function (): void {
+					add_filter(
+						'od_url_metric_schema_element_item_additional_properties',
+						static function ( array $properties ): array {
+							$properties['isColorful'] = array(
+								'type' => 'boolean',
+							);
+							return $properties;
+						}
+					);
+				},
+				'data'   => array(
+					'url'       => home_url( '/' ),
+					'viewport'  => $viewport,
+					'timestamp' => microtime( true ),
+					'elements'  => array( $valid_element ),
+				),
+				'assert' => function ( OD_URL_Metric $extended_url_metric, OD_URL_Metric $original_url_metric ): void {
+					$this->assertSame( $original_url_metric->get_viewport(), $extended_url_metric->get_viewport() );
+
+					$original_data = $original_url_metric->jsonSerialize();
+					$this->assertArrayNotHasKey( 'isColorful', $original_data['elements'][0] );
+
+					$extended_data = $extended_url_metric->jsonSerialize();
+					$this->assertArrayNotHasKey( 'isColorful', $extended_data['elements'][0] );  // If rest_sanitize_value_from_schema() took default into account (and we allowed defaults), this could be different.
 				},
 			),
 
-			'added_invalid_element_property' => array(
+			'added_invalid_element_property'             => array(
 				'set_up' => static function (): void {
 					add_filter(
 						'od_url_metric_schema_element_item_additional_properties',
@@ -503,6 +563,30 @@ static function ( $additional_properties ) {
 				'expected_incorrect_usage' => 'Filter: &#039;od_url_metric_schema_root_additional_properties&#039;',
 			),
 
+			'bad_default'                    => array(
+				'set_up'                   => static function (): void {
+					add_filter(
+						'od_url_metric_schema_root_additional_properties',
+						static function ( $additional_properties ) {
+							$additional_properties['foo'] = array(
+								'type'    => 'string',
+								'default' => 'bar',
+							);
+							return $additional_properties;
+						}
+					);
+				},
+				'assert'                   => function ( array $original_schema, $extended_schema ): void {
+					$expected_schema = $original_schema;
+					$expected_schema['properties']['foo'] = array(
+						'type'     => 'string',
+						'required' => false,
+					);
+					$this->assertSame( $expected_schema, $extended_schema );
+				},
+				'expected_incorrect_usage' => 'Filter: &#039;od_url_metric_schema_root_additional_properties&#039;',
+			),
+
 			'bad_existing_root_property'     => array(
 				'set_up'                   => static function (): void {
 					add_filter(

From 8917ce990922a6ee28d3f482f7989df30e29926e Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Tue, 10 Sep 2024 13:57:01 -0700
Subject: [PATCH 14/16] Explicitly fork
 rest_default_additional_properties_to_false()

---
 .../class-od-strict-url-metric.php            | 40 +++++++++++++------
 1 file changed, 28 insertions(+), 12 deletions(-)

diff --git a/plugins/optimization-detective/class-od-strict-url-metric.php b/plugins/optimization-detective/class-od-strict-url-metric.php
index 89d1196435..d3e0a5a5da 100644
--- a/plugins/optimization-detective/class-od-strict-url-metric.php
+++ b/plugins/optimization-detective/class-od-strict-url-metric.php
@@ -30,34 +30,50 @@ final class OD_Strict_URL_Metric extends OD_URL_Metric {
 	 * @return array<string, mixed> Schema.
 	 */
 	public static function get_json_schema(): array {
-		return self::falsify_additional_properties( parent::get_json_schema() );
+		return self::set_additional_properties_to_false( parent::get_json_schema() );
 	}
 
 	/**
 	 * Recursively processes the schema to ensure that all objects have additionalProperties set to false.
 	 *
+	 * This is a forked version of `rest_default_additional_properties_to_false()` which isn't being used itself because
+	 * it does not override `additionalProperties` to be false, but rather only sets it when it is empty.
+	 *
 	 * @since n.e.x.t
+	 * @see rest_default_additional_properties_to_false()
 	 *
 	 * @param mixed $schema Schema.
 	 * @return mixed Processed schema.
 	 */
-	private static function falsify_additional_properties( $schema ) {
+	private static function set_additional_properties_to_false( $schema ) {
 		if ( ! isset( $schema['type'] ) ) {
 			return $schema;
 		}
-		if ( 'object' === $schema['type'] ) {
+
+		$type = (array) $schema['type'];
+
+		if ( in_array( 'object', $type, true ) ) {
+			if ( isset( $schema['properties'] ) ) {
+				foreach ( $schema['properties'] as $key => $child_schema ) {
+					$schema['properties'][ $key ] = self::set_additional_properties_to_false( $child_schema );
+				}
+			}
+
+			if ( isset( $schema['patternProperties'] ) ) {
+				foreach ( $schema['patternProperties'] as $key => $child_schema ) {
+					$schema['patternProperties'][ $key ] = self::set_additional_properties_to_false( $child_schema );
+				}
+			}
+
 			$schema['additionalProperties'] = false;
-			if ( isset( $schema['properties'] ) && is_array( $schema['properties'] ) ) {
-				$schema['properties'] = array_map(
-					static function ( $property_schema ) {
-						return self::falsify_additional_properties( $property_schema );
-					},
-					$schema['properties']
-				);
+		}
+
+		if ( in_array( 'array', $type, true ) ) {
+			if ( isset( $schema['items'] ) ) {
+				$schema['items'] = self::set_additional_properties_to_false( $schema['items'] );
 			}
-		} elseif ( 'array' === $schema['type'] && isset( $schema['items'] ) && is_array( $schema['items'] ) ) {
-			$schema['items'] = self::falsify_additional_properties( $schema['items'] );
 		}
+
 		return $schema;
 	}
 }

From 907d8c3ba344d1247fa48a39c7b23512da2ba07a Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Tue, 10 Sep 2024 13:59:00 -0700
Subject: [PATCH 15/16] Add return description for magic getter

---
 plugins/optimization-detective/class-od-url-metric.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/plugins/optimization-detective/class-od-url-metric.php b/plugins/optimization-detective/class-od-url-metric.php
index 261423b776..3c27631b44 100644
--- a/plugins/optimization-detective/class-od-url-metric.php
+++ b/plugins/optimization-detective/class-od-url-metric.php
@@ -373,7 +373,7 @@ public function get( string $key ) {
 	 * @since n.e.x.t
 	 *
 	 * @param string $key Property.
-	 * @return mixed|null
+	 * @return mixed|null The property value, or null if not set.
 	 */
 	public function __get( string $key ) {
 		return $this->get( $key );

From 0db296f40002a7c2a13b88ca415928b2fa1644c4 Mon Sep 17 00:00:00 2001
From: Weston Ruter <westonruter@google.com>
Date: Wed, 11 Sep 2024 15:08:34 -0700
Subject: [PATCH 16/16] Eliminate magic getter

Co-authored-by: felixarntz <flixos90@git.wordpress.org>
---
 .../class-od-url-metric.php                   | 21 -------------
 .../class-od-url-metrics-group-collection.php |  4 +--
 .../class-od-url-metrics-group.php            |  8 ++---
 .../class-od-url-metrics-post-type.php        |  4 +--
 .../tests/test-class-od-url-metric.php        | 30 +++++++------------
 5 files changed, 19 insertions(+), 48 deletions(-)

diff --git a/plugins/optimization-detective/class-od-url-metric.php b/plugins/optimization-detective/class-od-url-metric.php
index 3c27631b44..a64db2f1dd 100644
--- a/plugins/optimization-detective/class-od-url-metric.php
+++ b/plugins/optimization-detective/class-od-url-metric.php
@@ -44,12 +44,6 @@
  *                                elements: ElementData[]
  *                            }
  *
- * @property-read string        $uuid
- * @property-read string        $url
- * @property-read float         $timestamp
- * @property-read ViewportRect  $viewport
- * @property-read ElementData[] $elements
- *
  * @since 0.1.0
  * @access private
  */
@@ -364,21 +358,6 @@ public function get( string $key ) {
 		return $this->data[ $key ] ?? null;
 	}
 
-	/**
-	 * Gets property value for an arbitrary key.
-	 *
-	 * This is useful with the `@property-read` annotations for the class. For accessing other data,
-	 * it's likely the `get()` method will be more useful for static analysis reasons.
-	 *
-	 * @since n.e.x.t
-	 *
-	 * @param string $key Property.
-	 * @return mixed|null The property value, or null if not set.
-	 */
-	public function __get( string $key ) {
-		return $this->get( $key );
-	}
-
 	/**
 	 * Gets UUID.
 	 *
diff --git a/plugins/optimization-detective/class-od-url-metrics-group-collection.php b/plugins/optimization-detective/class-od-url-metrics-group-collection.php
index dd2306a73b..21bce9a0c5 100644
--- a/plugins/optimization-detective/class-od-url-metrics-group-collection.php
+++ b/plugins/optimization-detective/class-od-url-metrics-group-collection.php
@@ -193,7 +193,7 @@ private function create_groups(): array {
 	 */
 	public function add_url_metric( OD_URL_Metric $new_url_metric ): void {
 		foreach ( $this->groups as $group ) {
-			if ( $group->is_viewport_width_in_range( $new_url_metric->viewport['width'] ) ) {
+			if ( $group->is_viewport_width_in_range( $new_url_metric->get_viewport_width() ) ) {
 				$group->add_url_metric( $new_url_metric );
 				return;
 			}
@@ -416,7 +416,7 @@ public function get_all_element_max_intersection_ratios(): array {
 			 */
 			foreach ( $this->groups as $group ) {
 				foreach ( $group as $url_metric ) {
-					foreach ( $url_metric->elements as $element ) {
+					foreach ( $url_metric->get_elements() as $element ) {
 						$element_max_intersection_ratios[ $element['xpath'] ] = array_key_exists( $element['xpath'], $element_max_intersection_ratios )
 							? max( $element_max_intersection_ratios[ $element['xpath'] ], $element['intersectionRatio'] )
 							: $element['intersectionRatio'];
diff --git a/plugins/optimization-detective/class-od-url-metrics-group.php b/plugins/optimization-detective/class-od-url-metrics-group.php
index 6eb364aa19..97e1bf7cc7 100644
--- a/plugins/optimization-detective/class-od-url-metrics-group.php
+++ b/plugins/optimization-detective/class-od-url-metrics-group.php
@@ -181,7 +181,7 @@ public function is_viewport_width_in_range( int $viewport_width ): bool {
 	 * @param OD_URL_Metric $url_metric URL metric.
 	 */
 	public function add_url_metric( OD_URL_Metric $url_metric ): void {
-		if ( ! $this->is_viewport_width_in_range( $url_metric->viewport['width'] ) ) {
+		if ( ! $this->is_viewport_width_in_range( $url_metric->get_viewport_width() ) ) {
 			throw new InvalidArgumentException(
 				esc_html__( 'URL metric is not in the viewport range for group.', 'optimization-detective' )
 			);
@@ -201,7 +201,7 @@ public function add_url_metric( OD_URL_Metric $url_metric ): void {
 			usort(
 				$this->url_metrics,
 				static function ( OD_URL_Metric $a, OD_URL_Metric $b ): int {
-					return $b->timestamp <=> $a->timestamp;
+					return $b->get_timestamp() <=> $a->get_timestamp();
 				}
 			);
 
@@ -229,7 +229,7 @@ public function is_complete(): bool {
 			}
 			$current_time = microtime( true );
 			foreach ( $this->url_metrics as $url_metric ) {
-				if ( $current_time > $url_metric->timestamp + $this->freshness_ttl ) {
+				if ( $current_time > $url_metric->get_timestamp() + $this->freshness_ttl ) {
 					return false;
 				}
 			}
@@ -283,7 +283,7 @@ public function get_lcp_element(): ?array {
 			$breadcrumb_element = array();
 
 			foreach ( $this->url_metrics as $url_metric ) {
-				foreach ( $url_metric->elements as $element ) {
+				foreach ( $url_metric->get_elements() as $element ) {
 					if ( ! $element['isLCP'] ) {
 						continue;
 					}
diff --git a/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php b/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
index 8bfcccd096..43079459a1 100644
--- a/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
+++ b/plugins/optimization-detective/storage/class-od-url-metrics-post-type.php
@@ -200,7 +200,7 @@ public static function store_url_metric( string $slug, OD_URL_Metric $new_url_me
 			// multiple URL Metric instances, each of which also contains the URL for which the metric was captured. The URL
 			// appearing in the post title is therefore the most recent URL seen for the URL Metrics which have the same
 			// normalized query vars among them.
-			'post_title' => $new_url_metric->url,
+			'post_title' => $new_url_metric->get_url(),
 		);
 
 		$post = self::get_post( $slug );
@@ -221,7 +221,7 @@ public static function store_url_metric( string $slug, OD_URL_Metric $new_url_me
 		);
 
 		try {
-			$group = $group_collection->get_group_for_viewport_width( $new_url_metric->viewport['width'] );
+			$group = $group_collection->get_group_for_viewport_width( $new_url_metric->get_viewport_width() );
 			$group->add_url_metric( $new_url_metric );
 		} catch ( InvalidArgumentException $e ) {
 			return new WP_Error( 'invalid_url_metric', $e->getMessage() );
diff --git a/plugins/optimization-detective/tests/test-class-od-url-metric.php b/plugins/optimization-detective/tests/test-class-od-url-metric.php
index b3732b6ae7..0f9370a0b1 100644
--- a/plugins/optimization-detective/tests/test-class-od-url-metric.php
+++ b/plugins/optimization-detective/tests/test-class-od-url-metric.php
@@ -204,7 +204,7 @@ static function ( $value ) {
 	 * @covers ::get_elements
 	 * @covers ::jsonSerialize
 	 * @covers ::get
-	 * @covers ::__get
+	 * @covers ::get_json_schema
 	 *
 	 * @dataProvider data_provider_to_test_constructor
 	 *
@@ -220,31 +220,25 @@ public function test_constructor( array $data, string $error = '' ): void {
 
 		$this->assertSame( array_map( 'intval', $data['viewport'] ), $url_metric->get_viewport() );
 		$this->assertSame( array_map( 'intval', $data['viewport'] ), $url_metric->get( 'viewport' ) );
-		$this->assertSame( array_map( 'intval', $data['viewport'] ), $url_metric->viewport );
 		$this->assertSame( (int) $data['viewport']['width'], $url_metric->get_viewport_width() );
-		$this->assertSame( (int) $data['viewport']['width'], $url_metric->viewport['width'] );
 
 		$this->assertSame( (float) $data['timestamp'], $url_metric->get_timestamp() );
 		$this->assertSame( (float) $data['timestamp'], $url_metric->get( 'timestamp' ) );
-		$this->assertSame( (float) $data['timestamp'], $url_metric->timestamp );
 
-		$this->assertCount( count( $data['elements'] ), $url_metric->elements );
+		$this->assertCount( count( $data['elements'] ), $url_metric->get_elements() );
 		for ( $i = 0, $length = count( $data['elements'] ); $i < $length; $i++ ) {
-			$this->assertSame( (bool) $data['elements'][ $i ]['isLCP'], $url_metric->elements[ $i ]['isLCP'] );
-			$this->assertSame( (bool) $data['elements'][ $i ]['isLCPCandidate'], $url_metric->elements[ $i ]['isLCPCandidate'] );
-			$this->assertSame( (float) $data['elements'][ $i ]['intersectionRatio'], $url_metric->elements[ $i ]['intersectionRatio'] );
-			$this->assertSame( array_map( 'floatval', $data['elements'][ $i ]['boundingClientRect'] ), $url_metric->elements[ $i ]['boundingClientRect'] );
-			$this->assertSame( array_map( 'floatval', $data['elements'][ $i ]['intersectionRect'] ), $url_metric->elements[ $i ]['intersectionRect'] );
+			$this->assertSame( (bool) $data['elements'][ $i ]['isLCP'], $url_metric->get_elements()[ $i ]['isLCP'] );
+			$this->assertSame( (bool) $data['elements'][ $i ]['isLCPCandidate'], $url_metric->get_elements()[ $i ]['isLCPCandidate'] );
+			$this->assertSame( (float) $data['elements'][ $i ]['intersectionRatio'], $url_metric->get_elements()[ $i ]['intersectionRatio'] );
+			$this->assertSame( array_map( 'floatval', $data['elements'][ $i ]['boundingClientRect'] ), $url_metric->get_elements()[ $i ]['boundingClientRect'] );
+			$this->assertSame( array_map( 'floatval', $data['elements'][ $i ]['intersectionRect'] ), $url_metric->get_elements()[ $i ]['intersectionRect'] );
 		}
-		$this->assertSame( $url_metric->elements, $url_metric->get_elements() );
-		$this->assertSame( $url_metric->elements, $url_metric->get( 'elements' ) );
+		$this->assertSame( $url_metric->get_elements(), $url_metric->get( 'elements' ) );
 
 		$this->assertSame( $data['url'], $url_metric->get_url() );
 		$this->assertSame( $data['url'], $url_metric->get( 'url' ) );
-		$this->assertSame( $data['url'], $url_metric->url );
 
 		$this->assertTrue( wp_is_uuid( $url_metric->get_uuid() ) );
-		$this->assertSame( $url_metric->get_uuid(), $url_metric->uuid );
 		$this->assertSame( $url_metric->get_uuid(), $url_metric->get( 'uuid' ) );
 
 		$serialized = $url_metric->jsonSerialize();
@@ -394,12 +388,12 @@ static function ( array $properties ): array {
 					$original_data = $original_url_metric->jsonSerialize();
 					$this->assertArrayHasKey( 'isColorful', $original_data['elements'][0] );
 					$this->assertSame( 'false', $original_data['elements'][0]['isColorful'] );
-					$this->assertSame( 'false', $original_url_metric->elements[0]['isColorful'] );
+					$this->assertSame( 'false', $original_url_metric->get_elements()[0]['isColorful'] );
 
 					$extended_data = $extended_url_metric->jsonSerialize();
 					$this->assertArrayHasKey( 'isColorful', $extended_data['elements'][0] );
 					$this->assertFalse( $extended_data['elements'][0]['isColorful'] );
-					$this->assertFalse( $extended_url_metric->elements[0]['isColorful'] );
+					$this->assertFalse( $extended_url_metric->get_elements()[0]['isColorful'] );
 				},
 			),
 
@@ -464,9 +458,7 @@ static function ( array $properties ): array {
 	/**
 	 * Tests construction with extended schema.
 	 *
-	 * @covers ::jsonSerialize
-	 * @covers ::get
-	 * @covers ::__get
+	 * @covers ::get_json_schema
 	 *
 	 * @dataProvider data_provider_to_test_constructor_with_extended_schema
 	 *