Introduce general namespace support, using dcterms as an example (#1893)

Author: pfefferle

.github/changelog/1893-from-description

@@ -0,0 +1,4 @@
+Significance: minor
+Type: added
+
+Added support for namespaced attributes and the dcterms:subject field (FEP-b2b8), as a first step toward phasing out summary-based content warnings.

includes/activity/class-base-object.php

@@ -32,6 +32,7 @@ class Base_Object extends Generic_Object {
 		array(
 			'Hashtag'   => 'as:Hashtag',
 			'sensitive' => 'as:sensitive',
+			'dcterms'   => 'http://purl.org/dc/terms/',
 		),
 	);
 
@@ -416,6 +417,16 @@ class Base_Object extends Generic_Object {
 	 */
 	protected $sensitive;
 
+	/**
+	 * The dcterms namespace.
+	 *
+	 * @see https://codeberg.org/fediverse/fep/src/branch/main/fep/b2b8/fep-b2b8.md#sensitive
+	 * @see https://www.dublincore.org/specifications/dublin-core/dcmi-terms/
+	 *
+	 * @var array
+	 */
+	protected $dcterms;
+
 	/**
 	 * Generic getter.
 	 *

includes/activity/class-generic-object.php

@@ -297,8 +297,11 @@ public function to_array( $include_json_ld_context = true ) {
 				$value = $value->to_array( false );
 			}
 
-			// If value is still empty, ignore it for the array and continue.
-			if ( isset( $value ) ) {
+			if ( is_array( $value ) && $this->is_namespaced( $key ) ) {
+				foreach ( $value as $sub_key => $sub_value ) {
+					$array[ snake_to_camel_case( $key ) . ':' . snake_to_camel_case( $sub_key ) ] = $sub_value;
+				}
+			} elseif ( isset( $value ) ) {
 				$array[ snake_to_camel_case( $key ) ] = $value;
 			}
 		}
@@ -373,4 +376,23 @@ public function get_object_var_keys() {
 	public function get_json_ld_context() {
 		return static::JSON_LD_CONTEXT;
 	}
+
+	/**
+	 * Checks if an attribute is in a namespace.
+	 *
+	 * @param string $attribute The attribute to check.
+	 *
+	 * @return bool Whether the attribute is namespaced.
+	 */
+	private function is_namespaced( $attribute ) {
+		$namespaces = array();
+
+		foreach ( static::JSON_LD_CONTEXT as $context ) {
+			if ( is_array( $context ) ) {
+				$namespaces = \array_merge( $namespaces, $context );
+			}
+		}
+
+		return isset( $namespaces[ $attribute ] ) && \wp_http_validate_url( $namespaces[ $attribute ] );
+	}
 }

includes/transformer/class-post.php

@@ -57,6 +57,7 @@ public function to_object() {
 			$object->set_sensitive( true );
 			$object->set_summary( $content_warning );
 			$object->set_summary_map( null );
+			$object->set_dcterms( array( 'subject' => $content_warning ) );
 		}
 
 		return $object;

tests/includes/collection/class-test-outbox.php

@@ -115,7 +115,7 @@ public function activity_object_provider() {
 				),
 				'Create',
 				1,
-				'{"@context":["https:\/\/www.w3.org\/ns\/activitystreams",{"Hashtag":"as:Hashtag","sensitive":"as:sensitive"}],"actor":"http:\/\/example.org\/?author=1","id":"http:\/\/example.org\/?post_type=ap_outbox\u0026p=351","type":"Create","to":["https:\/\/www.w3.org\/ns\/activitystreams#Public"],"object":{"id":"https:\/\/example.com\/1","type":"Note","content":"\u003Cp\u003EThis is a note\u003C\/p\u003E","contentMap":{"en":"\u003Cp\u003EThis is a note\u003C\/p\u003E"},"tag":[],"to":["https:\/\/www.w3.org\/ns\/activitystreams#Public"],"mediaType":"text\/html"}}',
+				'{"@context":["https:\/\/www.w3.org\/ns\/activitystreams",{"Hashtag":"as:Hashtag","sensitive":"as:sensitive","dcterms":"http:\/\/purl.org\/dc\/terms\/"}],"actor":"http:\/\/example.org\/?author=1","id":"http:\/\/example.org\/?post_type=ap_outbox\u0026p=351","type":"Create","to":["https:\/\/www.w3.org\/ns\/activitystreams#Public"],"object":{"id":"https:\/\/example.com\/1","type":"Note","content":"\u003Cp\u003EThis is a note\u003C\/p\u003E","contentMap":{"en":"\u003Cp\u003EThis is a note\u003C\/p\u003E"},"tag":[],"to":["https:\/\/www.w3.org\/ns\/activitystreams#Public"],"mediaType":"text\/html"}}',
 			),
 			array(
 				array(
@@ -126,7 +126,7 @@ public function activity_object_provider() {
 				),
 				'Create',
 				2,
-				'{"@context":["https:\/\/www.w3.org\/ns\/activitystreams",{"Hashtag":"as:Hashtag","sensitive":"as:sensitive"}],"actor":"http:\/\/example.org\/?author=0","id":"http:\/\/example.org\/?post_type=ap_outbox\u0026p=352","type":"Create","to":["https:\/\/www.w3.org\/ns\/activitystreams#Public"],"object":{"id":"https:\/\/example.com\/2","type":"Note","content":"\u003Cp\u003EThis is another note\u003C\/p\u003E","contentMap":{"en":"\u003Cp\u003EThis is another note\u003C\/p\u003E"},"tag":[],"to":["https:\/\/www.w3.org\/ns\/activitystreams#Public"],"mediaType":"text\/html"}}',
+				'{"@context":["https:\/\/www.w3.org\/ns\/activitystreams",{"Hashtag":"as:Hashtag","sensitive":"as:sensitive","dcterms":"http:\/\/purl.org\/dc\/terms\/"}],"actor":"http:\/\/example.org\/?author=0","id":"http:\/\/example.org\/?post_type=ap_outbox\u0026p=352","type":"Create","to":["https:\/\/www.w3.org\/ns\/activitystreams#Public"],"object":{"id":"https:\/\/example.com\/2","type":"Note","content":"\u003Cp\u003EThis is another note\u003C\/p\u003E","contentMap":{"en":"\u003Cp\u003EThis is another note\u003C\/p\u003E"},"tag":[],"to":["https:\/\/www.w3.org\/ns\/activitystreams#Public"],"mediaType":"text\/html"}}',
 			),
 			array(
 				Event::init_from_array(