WordPress at a glance
filter is not described

pre_upload_error filter-hook . WP 2.1.0

Filters whether to preempt the XML-RPC media upload.

Passing a truthy value will effectively short-circuit the media upload, returning that value as a 500 error instead.

Usage

add_filter( 'pre_upload_error', 'filter_function_name_7759' );
function filter_function_name_7759( $error ){
	// filter...

	return $error;
}
$error(true/false)
Whether to pre-empt the media upload.
Default: false

Where the hook is called

wp_xmlrpc_server::mw_newMediaObject()
wp-includes/class-wp-xmlrpc-server.php 5931
if ( $upload_err = apply_filters( 'pre_upload_error', false ) ) {

Where the hook is used (in WP core)

Does not used.