Better error message if hook function signature does not match parameters.

Also took the opportunity to write a short essay why this made me annoyed.

diff --git a/includes/Hooks.php b/includes/Hooks.php
index dec1c44..01810b2 100644 (file)
--- a/includes/Hooks.php
+++ b/includes/Hooks.php
@@ -55,6 +55,7 @@ function wfRunHooks($event, $args = array()) {
                $data = null;
                $have_data = false;
                $closure = false;
+               $badhookmsg = false;
 
                /* $hook can be: a function, an object, an array of $function and $data,
                 * an array of just a function, an array of object and method, or an
@@ -128,10 +129,34 @@ function wfRunHooks($event, $args = array()) {
                // Run autoloader (workaround for call_user_func_array bug)
                is_callable( $callback );
 
-               /* Call the hook. */
+               /* Call the hook. The documentation of call_user_func_array clearly
+                * states that FALSE is returned on failure. However this is not
+                * case always. In some version of PHP if the function signature
+                * does not match the call signature, PHP will issue an warning:
+                * Param y in x expected to be a reference, value given.
+                *
+                * In that case the call will also return null. The following code
+                * catches that warning and provides better error message. The
+                * function documentation also says that:
+                *     In other words, it does not depend on the function signature
+                *     whether the parameter is passed by a value or by a reference. 
+                * There is also PHP bug http://bugs.php.net/bug.php?id=47554 which
+                * is unsurprisingly marked as bogus. In short handling of failures
+                * with call_user_func_array is a failure, the documentation for that
+                * function is wrong and misleading and PHP developers don't see any
+                * problem here.
+                */
+               $retval = null;
+               $handler = set_error_handler( 'hookErrorHandler' );
                wfProfileIn( $func );
-               $retval = call_user_func_array( $callback, $hook_args );
+               try {
+                       $retval = call_user_func_array( $callback, $hook_args );
+               } catch ( MWHookException $e ) {
+                       $badhookmsg = $e->getMessage();
+               }
                wfProfileOut( $func );
+               // Need to check for null, because set_error_handler borks on it... sigh
+               if ( $handler !== null ) set_error_handler( $handler );
 
                /* String return is an error; false return means stop processing. */
 
@@ -152,9 +177,14 @@ function wfRunHooks($event, $args = array()) {
                        } else {
                                $prettyFunc = strval( $callback );
                        }
-                       throw new MWException( "Detected bug in an extension! " .
-                               "Hook $prettyFunc failed to return a value; " .
-                               "should return true to continue hook processing or false to abort." );
+                       if ( $badhookmsg ) {
+                               throw new MWException( "Detected bug in an extension! " .
+                               "Hook $prettyFunc has invalid call signature; " . $badhookmsg );
+                       } else {
+                               throw new MWException( "Detected bug in an extension! " .
+                                       "Hook $prettyFunc failed to return a value; " .
+                                       "should return true to continue hook processing or false to abort." );
+                       }
                } else if ( !$retval ) {
                        return false;
                }
@@ -162,3 +192,12 @@ function wfRunHooks($event, $args = array()) {
 
        return true;
 }
+
+function hookErrorHandler( $errno, $errstr ) {
+       if ( strpos( $errstr, 'expected to be a reference, value given' ) !== false ) {
+               throw new MWHookException( $errstr );
+       }
+       return false;
+}
+
+class MWHookException extends MWException {}
\ No newline at end of file