Query loop / Post template: Enable post format filter (#64167)

Enables filtering the query loop result by post format.

To allow querying a given post format, a new parameter, `format` is added to a new compatibility class called `Gutenberg_REST_Posts_Controller_6_7`, which extends the core class `WP_REST_Posts_Controller`.

Query loop block:
- Adds a new parameter, `format`, to the `query` attribute in block.json.
- Adds a new `FormatControls` that uses a list of supported post formats inside a `FormTokenField`. This control is placed in the `Filters` panel in the block settings sidebar.
- Adds a new utility function `gutenberg_add_format_query_vars_to_query_loop_block` to ensure that the Query loop block can pass the new `format` argument correctly to `WP_Query`. This function is hooked into `query_loop_block_query_vars`.

Post Template block:
The new `format` parameter is passed from the query loop block to the post template block as part of the `query` attribute.

---------

Co-authored-by: carolinan <[email protected]>
Co-authored-by: Mamaduka <[email protected]>
Co-authored-by: youknowriad <[email protected]>
Co-authored-by: ntsekouras <[email protected]>
Co-authored-by: dmsnell <[email protected]>
Co-authored-by: TimothyBJacobs <[email protected]>
Co-authored-by: nickbohle <[email protected]>
Co-authored-by: SergeyBiryukov <[email protected]>
Co-authored-by: justintadlock <[email protected]>

backport-changelog/6.7/7314.md

@@ -0,0 +1,3 @@
+https://github.com/WordPress/wordpress-develop/pull/7314
+
+* https://github.com/WordPress/gutenberg/pull/64167

lib/compat/wordpress-6.7/blocks.php

@@ -43,3 +43,63 @@ function gutenberg_filter_block_type_metadata_settings_allow_variations_php_file
 	return $settings;
 }
 add_filter( 'block_type_metadata_settings', 'gutenberg_filter_block_type_metadata_settings_allow_variations_php_file', 10, 2 );
+
+/**
+ * Adds post format query vars to the query loop block's WP_Query when the block's attributes call for them.
+ *
+ * @see 'query_loop_block_query_vars'
+ *
+ * @param array    $query The query vars.
+ * @param WP_Block $block Block instance.
+ * @return array   The filtered query vars.
+ */
+function gutenberg_add_format_query_vars_to_query_loop_block( $query, $block ) {
+	// Return early if there is no format or if the format is not an array.
+	if ( empty( $block->context['query']['format'] ) || ! is_array( $block->context['query']['format'] ) ) {
+		return $query;
+	}
+
+	$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',
+		);
+	}
+
+	// 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;
+	}
+
+	return $query;
+}
+add_filter( 'query_loop_block_query_vars', 'gutenberg_add_format_query_vars_to_query_loop_block', 10, 2 );