Issue #1201024 by pillarsdotnet, jbrown, tim.plunkett | Damien Tournoud: drupal_realpath() should describe when it should be used.

includes/file.inc

@@ -2199,29 +2199,21 @@ function drupal_unlink($uri, $context = NULL) {
 }
 
 /**
- * Returns the absolute local filesystem path of a stream URI.
+ * Resolves the absolute filepath of a local URI or filepath.
  *
- * This function was originally written to ease the conversion of 6.x code to
- * use 7.x stream wrappers. However, it assumes that every URI may be resolved
- * to an absolute local filesystem path, and this assumption fails when stream
- * wrappers are used to support remote file storage. Remote stream wrappers
- * may implement the realpath method by always returning FALSE. The use of
- * drupal_realpath() is discouraged, and is slowly being removed from core
- * functions where possible.
+ * The use of drupal_realpath() is discouraged, because it does not work for
+ * remote URIs. Except in rare cases, URIs should not be manually resolved.
  *
  * Only use this function if you know that the stream wrapper in the URI uses
  * the local file system, and you need to pass an absolute path to a function
  * that is incompatible with stream URIs.
  *
- * @param $uri
- *   A stream wrapper URI or a filesystem path, possibly including one or more
- *   symbolic links.
+ * @param string $uri
+ *   A stream wrapper URI or a filepath, possibly including one or more symbolic
+ *   links.
  *
- * @return
- *   The absolute local filesystem path (with no symbolic links), or FALSE on
- *   failure.
- *
- * @todo This function is deprecated, and should be removed wherever possible.
+ * @return string|false
+ *   The absolute local filepath (with no symbolic links), or FALSE on failure.
  *
  * @see DrupalStreamWrapperInterface::realpath()
  * @see http://php.net/manual/function.realpath.php