Redirect to current page after wordpress login

You can use the login_redirect filter to do this. One of the parameters is $request, which

is the URL the user is coming from

function wpse125952_redirect_to_request( $redirect_to, $request, $user ){
    // instead of using $redirect_to we're redirecting back to $request
    return $request;
}
add_filter('login_redirect', 'wpse125952_redirect_to_request', 10, 3);

The filter could additionally easily be used for distinguishing redirect destinations by user roles. Take a look at the documentation for a deeper insight into that.