Docs: Link to the "Conditional Tags" article in the Theme Developer Handbook from the descriptions for a variety of core conditional tag functions.

These notations largely serve to direct consumers (of both the source and the parsed code reference) to extended information on individual and related conditional tags throughout WordPress. The changeset also standardizes corresponding DocBlock summaries to use third-person singular verbs.

Notations been added for the following functions:

* comments_open()
* email exists()
* has_excerpt()
* has_post_thumbnail()
* has_tag()
* in_category()
* in_the_loop()
* is_404()
* is_active_sidebar()
* is_active_widget()
* is_admin()
* is_admin_bar_showing()
* is_archive()
* is_attachment()
* is_author()
* is_blog_installed()
* is_category()
* is_comments_popup()
* is_date()
* is_day()
* is_dynamic_sidebar()
* is_feed()
* is_front_page()
* is_home()
* is_local_attachment()
* is_main_query
* is_month()
* is_multi_author
* is_new_day()
* is_page()
* is_page_template()
* is_paged()
* is_plugin_active()
* is_plugin_active_for_network()
* is_plugin_inactive()
* is_plugin_page()
* is_post_type_archive()
* is_preview()
* is_rtl()
* is_search()
* is_single()
* is_singular()
* is_sticky()
* is_tag()
* is_tax()
* is_taxonomy_hierarchical()
* is_time()
* is_trackback()
* is_user_logged_in()
* is_year()
* pings_open()
* post_type_exists()
* taxonomy_exists()
* term_exists()
* username exists()
* wp_attachment_is_image()
* wp_script_is()

Props janalwin.
Fixes #43254.

Built from https://develop.svn.wordpress.org/trunk@42710


git-svn-id: http://core.svn.wordpress.org/trunk@42538 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/widgets.php

@@ -801,7 +801,7 @@ function dynamic_sidebar( $index = 1 ) {
 }
 
 /**
- * Whether widget is displayed on the front end.
+ * Determines whether a given widget is displayed on the front end.
  *
  * Either $callback or $id_base can be used
  * $id_base is the first argument when extending WP_Widget class
@@ -812,7 +812,11 @@ function dynamic_sidebar( $index = 1 ) {
  *
  * NOTE: $widget_id and $id_base are the same for single widgets. To be effective
  * this function has to run after widgets have initialized, at action {@see 'init'} or later.
- *
+ * 
+ * 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 2.2.0
  *
  * @global array $wp_registered_widgets
@@ -849,8 +853,12 @@ function is_active_widget( $callback = false, $widget_id = false, $id_base = fal
 }
 
 /**
- * Whether the dynamic sidebar is enabled and used by theme.
- *
+ * Determines whether the dynamic sidebar is enabled and used by the theme.
+ * 
+ * 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 2.2.0
  *
  * @global array $wp_registered_widgets
@@ -874,8 +882,12 @@ function is_dynamic_sidebar() {
 }
 
 /**
- * Whether a sidebar is in use.
- *
+ * Determines whether a sidebar is in use.
+ * 
+ * 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 2.8.0
  *
  * @param string|int $index Sidebar name, id or number to check.