Add support for the format property in query

src/wp-includes/blocks.php

@@ -2330,6 +2330,7 @@ function wp_migrate_old_typography_shape( $metadata ) {
  *
  * @since 5.8.0
  * @since 6.1.0 Added `query_loop_block_query_vars` filter and `parents` support in query.
+ * @since 6.7.0 Added support for the `format` property in query.
  *
  * @param WP_Block $block Block instance.
  * @param int      $page  Current query's page.
@@ -2420,6 +2421,52 @@ function build_query_vars_from_query_block( $block, $page ) {
 				}
 			}
 		}
+		if ( ! empty( $block->context['query']['format'] ) && is_array( $block->context['query']['format'] ) ) {
+			$formats   = $block->context['query']['format'];
+			$tax_query = array( 'relation' => 'OR' );
+
+			/*
+			 * The default post format, `standard`, is not stored in the database.
+			 * If `standard` is part of the request, the query needs to exclude all post items that
+			 * have a format assigned.
+			 */
+			if ( in_array( 'standard', $formats, true ) ) {
+				$tax_query[] = array(
+					'taxonomy' => 'post_format',
+					'field'    => 'slug',
+					'terms'    => array(),
+					'operator' => 'NOT EXISTS',
+				);
+				// Remove the `standard` format, since it cannot be queried.
+				unset( $formats[ array_search( 'standard', $formats, true ) ] );
+			}
+			// Add any remaining formats to the tax query.
+			if ( ! empty( $formats ) ) {
+				// Add the `post-format-` prefix.
+				$terms = array_map(
+					static function ( $format ) {
+						return 'post-format-' . $format;
+					},
+					$formats
+				);
+				$tax_query[] = array(
+					'taxonomy' => 'post_format',
+					'field'    => 'slug',
+					'terms'    => $terms,
+					'operator' => 'IN',
+				);
+			}
+			if ( ! isset( $query['tax_query'] ) ) {
+				$query['tax_query'] = array();
+			}
+			/*
+			 * This condition is intended to prevent `$tax_query` from being added to `$query`
+			 * if it only contains the relation.
+			 */
+			if ( count( $tax_query ) > 1 ) {
+				$query['tax_query'][] = $tax_query;
+			}
+		}
 		if (
 			isset( $block->context['query']['order'] ) &&
 				in_array( strtoupper( $block->context['query']['order'] ), array( 'ASC', 'DESC' ), true )

src/wp-includes/rest-api/endpoints/class-wp-rest-posts-controller.php

@@ -339,6 +339,55 @@ public function get_items( $request ) {
 
 		$args = $this->prepare_tax_query( $args, $request );
 
+		if ( ! empty( $request['format'] ) ) {
+			$formats   = $request['format'];
+			$tax_query = array( 'relation' => 'OR' );
+
+			/*
+			 * The default post format, `standard`, is not stored in the database.
+			 * If `standard` is part of the request, the query needs to exclude all post items that
+			 * have a format assigned.
+			 */
+			if ( in_array( 'standard', $formats, true ) ) {
+				$tax_query[] = array(
+					'taxonomy' => 'post_format',
+					'field'    => 'slug',
+					'terms'    => array(),
+					'operator' => 'NOT EXISTS',
+				);
+				// Remove the `standard` format, since it cannot be queried.
+				unset( $formats[ array_search( 'standard', $formats, true ) ] );
+			}
+
+			// Add any remaining formats to the tax query.
+			if ( ! empty( $formats ) ) {
+				// Add the `post-format-` prefix.
+				$terms = array_map(
+					static function ( $format ) {
+						return 'post-format-' . $format;
+					},
+					$formats
+				);
+
+				$tax_query[] = array(
+					'taxonomy' => 'post_format',
+					'field'    => 'slug',
+					'terms'    => $terms,
+					'operator' => 'IN',
+				);
+			}
+
+			// Enable filtering by both post formats and other taxonomies by combining them with `AND`.
+			if ( isset( $args['tax_query'] ) ) {
+				$args['tax_query'][] = array(
+					'relation' => 'AND',
+					$tax_query,
+				);
+			} else {
+				$args['tax_query'] = $tax_query;
+			}
+		}
+
 		// Force the post_type argument, since it's not a user input variable.
 		$args['post_type'] = $this->post_type;
 
@@ -2979,6 +3028,18 @@ public function get_collection_params() {
 			);
 		}
 
+		if ( post_type_supports( $this->post_type, 'post-formats' ) ) {
+			$query_params['format'] = array(
+				'description' => __( 'Limit result set to items assigned one or more given formats.' ),
+				'type'        => 'array',
+				'uniqueItems' => true,
+				'items'       => array(
+					'enum' => array_values( get_post_format_slugs() ),
+					'type' => 'string',
+				),
+			);
+		}
+
 		/**
 		 * Filters collection parameters for the posts controller.
 		 *

tests/phpunit/tests/rest-api/rest-posts-controller.php

@@ -196,6 +196,7 @@ public function test_registered_query_params() {
 				'categories_exclude',
 				'context',
 				'exclude',
+				'format',
 				'include',
 				'modified_after',
 				'modified_before',

tests/qunit/fixtures/wp-api-generated.js

@@ -618,6 +618,27 @@ mockedApiResponse.Schema = {
                             "description": "Limit result set to items that are sticky.",
                             "type": "boolean",
                             "required": false
+                        },
+                        "format": {
+                            "description": "Limit result set to items assigned one or more given formats.",
+                            "type": "array",
+                            "uniqueItems": true,
+                            "items": {
+                                "enum": [
+                                    "standard",
+                                    "aside",
+                                    "chat",
+                                    "gallery",
+                                    "link",
+                                    "image",
+                                    "quote",
+                                    "status",
+                                    "video",
+                                    "audio"
+                                ],
+                                "type": "string"
+                            },
+                            "required": false
                         }
                     }
                 },