Introduce new function to compute the current ETag

ShyamGadde · ShyamGadde · commit 8fe38f7d6bc4 · 2024-11-29T03:21:01.000+05:30
diff --git a/plugins/optimization-detective/class-od-url-metric-group.php b/plugins/optimization-detective/class-od-url-metric-group.php
@@ -239,7 +239,7 @@ public function is_complete(): bool {
 					$current_time > $url_metric->get_timestamp() + $this->freshness_ttl
 					||
 					// If the URL Metric's ETag doesn't match the current ETag, consider the URL metric as stale.
-					( null !== $this->collection && $url_metric->get_etag() !== $this->collection->get_current_etag() )
+					( null !== $this->collection && ! hash_equals( $url_metric->get_etag() ?? md5( '' ), $this->collection->get_current_etag() ) )
 				) {
 					return false;
 				}
diff --git a/plugins/optimization-detective/optimization.php b/plugins/optimization-detective/optimization.php
@@ -206,9 +206,7 @@ function od_optimize_template_output_buffer( string $buffer ): string {
 	 */
 	do_action( 'od_register_tag_visitors', $tag_visitor_registry );
 
-	$visitors     = iterator_to_array( $tag_visitor_registry );
-	$current_etag = implode( ',', array_keys( $visitors ) );
-
+	$current_etag         = od_compute_current_etag( $tag_visitor_registry );
 	$group_collection     = new OD_URL_Metric_Group_Collection(
 		$post instanceof WP_Post ? OD_URL_Metrics_Post_Type::get_url_metrics_from_post( $post ) : array(),
 		$current_etag,
@@ -219,6 +217,7 @@ function od_optimize_template_output_buffer( string $buffer ): string {
 	$link_collection      = new OD_Link_Collection();
 	$tag_visitor_context  = new OD_Tag_Visitor_Context( $processor, $group_collection, $link_collection );
 	$current_tag_bookmark = 'optimization_detective_current_tag';
+	$visitors             = iterator_to_array( $tag_visitor_registry );
 
 	// Whether we need to add the data-od-xpath attribute to elements and whether the detection script should be injected.
 	$needs_detection = ! $group_collection->is_every_group_complete();
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
@@ -224,7 +224,7 @@ public static function store_url_metric( string $slug, OD_URL_Metric $new_url_me
 			// However, in the context of this store_url_metric() method, which is called by the REST API callback,
 			// the ETag is a required field and should never be null. This usage satisfies PHPStan's requirements
 			// until a future release where get_etag() will always return a string.
-			$new_url_metric->get_etag() ?? '',
+			$new_url_metric->get_etag() ?? md5( '' ),
 			od_get_breakpoint_max_widths(),
 			od_get_url_metrics_breakpoint_sample_size(),
 			od_get_url_metric_freshness_ttl()
diff --git a/plugins/optimization-detective/storage/data.php b/plugins/optimization-detective/storage/data.php
@@ -140,6 +140,26 @@ function od_get_url_metrics_slug( array $query_vars ): string {
 	return md5( (string) wp_json_encode( $query_vars ) );
 }
 
+/**
+ * Computes the current ETag for URL Metrics.
+ *
+ * The ETag is a hash based on the IDs of the registered tag visitors
+ * in the current environment. It is used for marking the URL Metrics as stale
+ * when its value changes.
+ *
+ * @since n.e.x.t
+ * @access private
+ *
+ * @param OD_Tag_Visitor_Registry $tag_visitor_registry Tag visitor registry.
+ * @return string Current ETag.
+ */
+function od_compute_current_etag( OD_Tag_Visitor_Registry $tag_visitor_registry ): string {
+	$data = array(
+		'tag_visitors' => array_keys( iterator_to_array( $tag_visitor_registry ) ),
+	);
+	return md5( serialize( $data ) );  // phpcs:ignore WordPress.PHP.DiscouragedPHPFunctions.serialize_serialize
+}
+
 /**
  * Computes HMAC for storing URL Metrics for a specific slug.
  *

Original file line number	Diff line number	Diff line change
`@@ -239,7 +239,7 @@ public function is_complete(): bool {`
`239`	`239`	`$current_time > $url_metric->get_timestamp() + $this->freshness_ttl`
`240`	`240`	`\|\|`
`241`	`241`	`// If the URL Metric's ETag doesn't match the current ETag, consider the URL metric as stale.`
`242`		`- ( null !== $this->collection && $url_metric->get_etag() !== $this->collection->get_current_etag() )`
	`242`	`+ ( null !== $this->collection && ! hash_equals( $url_metric->get_etag() ?? md5( '' ), $this->collection->get_current_etag() ) )`
`243`	`243`	`) {`
`244`	`244`	`return false;`
`245`	`245`	`}`