Query: Add is_post_format_archive() conditional tag

src/wp-includes/class-wp-query.php

@@ -4408,6 +4408,27 @@ public function is_tax( $taxonomy = '', $term = '' ) {
 			);
 	}
 
+	/**
+	 * Is the query for an existing post format archive page?
+	 *
+	 * @since 7.2.0
+	 *
+	 * @param string|string[] $post_formats Optional. Post format or array of post formats
+	 *                                      to check against. Default empty.
+	 * @return bool Whether the query is for an existing post format archive page.
+	 */
+	public function is_post_format_archive( $post_formats = '' ) {
+		$prefixed_formats = array();
+
+		if ( $post_formats ) {
+			foreach ( (array) $post_formats as $post_format ) {
+				$prefixed_formats[] = 'post-format-' . sanitize_key( $post_format );
+			}
+		}
+
+		return $this->is_tax( 'post_format', $prefixed_formats );
+	}
+
 	/**
 	 * Determines whether the current URL is within the comments popup window.
 	 *

src/wp-includes/query.php

@@ -345,6 +345,35 @@ function is_tax( $taxonomy = '', $term = '' ) {
 	return $wp_query->is_tax( $taxonomy, $term );
 }
 
+/**
+ * Determines whether the query is for an existing post format archive page.
+ *
+ * If the $post_formats parameter is specified, this function will additionally
+ * check if the query is for one of the post formats specified.
+ *
+ * For more information on this and similar theme functions, check out
+ * the {@link https://developer.wordpress.org/themes/basics/conditional-tags/
+ * Conditional Tags} article in the Theme Developer Handbook.
+ *
+ * @since 7.2.0
+ *
+ * @global WP_Query $wp_query WordPress Query object.
+ *
+ * @param string|string[] $post_formats Optional. Post format or array of post formats
+ *                                      to check against. Default empty.
+ * @return bool Whether the query is for an existing post format archive page.
+ */
+function is_post_format_archive( $post_formats = '' ) {
+	global $wp_query;
+
+	if ( ! isset( $wp_query ) ) {
+		_doing_it_wrong( __FUNCTION__, __( 'Conditional query tags do not work before the query is run. Before then, they always return false.' ), '3.1.0' );
+		return false;
+	}
+
+	return $wp_query->is_post_format_archive( $post_formats );
+}
+
 /**
  * Determines whether the query is for an existing date archive.
  *

tests/phpunit/includes/abstract-testcase.php

@@ -1186,6 +1186,7 @@ public function assertQueryTrue( ...$prop ) {
 			'is_month',
 			'is_page',
 			'is_paged',
+			'is_post_format_archive',
 			'is_post_type_archive',
 			'is_posts_page',
 			'is_preview',

tests/phpunit/tests/query/conditionals.php

@@ -1598,6 +1598,35 @@ public function test_is_single_should_not_match_numeric_id_to_post_name_beginnin
 		$this->assertFalse( is_single( $p1 ) );
 	}
 
+	/**
+	 * @ticket 23749
+	 */
+	public function test_is_post_format_archive() {
+		$post_id = self::factory()->post->create();
+		set_post_format( $post_id, 'aside' );
+
+		$this->go_to( '/?post_format=aside' );
+
+		$this->assertQueryTrue( 'is_archive', 'is_tax', 'is_post_format_archive' );
+		$this->assertTrue( is_post_format_archive() );
+		$this->assertTrue( is_post_format_archive( 'aside' ) );
+		$this->assertTrue( is_post_format_archive( array( 'gallery', 'aside' ) ) );
+		$this->assertFalse( is_post_format_archive( 'gallery' ) );
+	}
+
+	/**
+	 * @ticket 23749
+	 */
+	public function test_is_post_format_archive_false_outside_a_post_format_archive() {
+		$post_id = self::factory()->post->create();
+		set_post_format( $post_id, 'aside' );
+
+		$this->go_to( get_permalink( $post_id ) );
+
+		$this->assertFalse( is_post_format_archive() );
+		$this->assertFalse( is_post_format_archive( 'aside' ) );
+	}
+
 	/**
 	 * @ticket 44005
 	 * @group privacy