Introduce doing_filter() and doing_action() to identify hooks in progress.

did_action() returns true the moment a hook is initially run, leaving you no way to tell if the hook is still in progress. Hooks can be nested and this checks the entire stack, versus current_filter() which only identifies the final hook in the stack. This commit also introduces current_action() for parity.

To tell if a hook has completed, one can use did_action() and ! doing_action() together.

The functions do not require an argument. In that situation, they indicate whether the stack is empty.

props ericmann for the initial unit tests.
fixes #14994.

Built from https://develop.svn.wordpress.org/trunk@27294


git-svn-id: http://core.svn.wordpress.org/trunk@27150 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/plugin.php

@@ -324,6 +324,61 @@ function current_filter() {
 	return end( $wp_current_filter );
 }
 
+/**
+ * Retrieve the name of the current action.
+ *
+ * @since 3.9.0
+ * @uses current_filter()
+ *
+ * @return string Hook name of the current action.
+ */
+function current_action() {
+	return current_filter();
+}
+
+/**
+ * Retrieve the name of a filter currently being processed.
+ *
+ * The function current_filter() only returns the most recent filter or action
+ * being executed.  did_action() returns true once the action is initially
+ * processed.  This function allows detection for any filter currently being
+ * executed (despite not being the most recent filter to fire, in the case of
+ * hooks called from hook callbacks) to be verified.
+ *
+ * @since 3.9.0
+ * @see current_filter()
+ * @see did_action()
+ *
+ * @param string $filter Optional. Filter to check. Defaults to null, which checks if any filter is currently being run.
+ *
+ * @global array $wp_current_filter
+ *
+ * @return bool Whether the filter is currently in the stack
+ */
+function doing_filter( $filter = null ) {
+	global $wp_current_filter;
+
+	if ( null === $filter ) {
+		return ! empty( $wp_current_filter );
+	}
+
+	return in_array( $filter, $wp_current_filter );
+}
+
+/**
+ * Retrieve the name of an action currently being processed.
+ *
+ * @since 3.9.0
+ * @uses doing_filter()
+ *
+ * @param string $action Optional. Action to check. Defaults to null, which checks if any action is currently being run.
+ *
+ * @return bool Whether the action is currently in the stack.
+ */
+function doing_action( $action = null ) {
+	return doing_filter( $action );
+}
+
 /**
  * Hooks a function on to a specific action.
  *