Add singular.php to template hierarchy

Singular is the only template context conditional that lacks a corresponding template. This allows some themes to simplify.

Fixes #22314.
Props chipbennett.



git-svn-id: https://develop.svn.wordpress.org/trunk@32846 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/template-loader.php

@@ -53,6 +53,7 @@ if ( defined('WP_USE_THEMES') && WP_USE_THEMES ) :
 		remove_filter('the_content', 'prepend_attachment');
 	elseif ( is_single()         && $template = get_single_template()         ) :
 	elseif ( is_page()           && $template = get_page_template()           ) :
+	elseif ( is_singular()       && $template = get_singular_template()       ) :
 	elseif ( is_category()       && $template = get_category_template()       ) :
 	elseif ( is_tag()            && $template = get_tag_template()            ) :
 	elseif ( is_author()         && $template = get_author_template()         ) :

src/wp-includes/template.php

@@ -382,6 +382,21 @@ function get_single_template() {
 	return get_query_template( 'single', $templates );
 }
 
+/**
+ * Retrieve path of singular template in current or parent template.
+ *
+ * The template path is filterable via the 'singular_template' hook.
+ *
+ * @since 4.3.0
+ *
+ * @see get_query_template()
+ *
+ * @return string Full path to singular template file
+ */
+function get_singular_template() {
+	return get_query_template( 'singular' );
+}
+
 /**
  * Retrieve path of attachment template in current or parent template.
  *