How to trigger sync and async imports

How does less decide to call loadFile or loadFileSync of the current fileManager? According to this code it requires an isSync-parameter to be set. But a short search for a call to getFileManager reveals that this option is only used by lib/less/functions/data-uri.js.

Is it possible to set this option explicitly when calling render()?

[ChiriVulpes]

Is there a renderSync yet? If not, is there a workaround for a synchronous render?

Edit: Nvm. For any future person who stumbles upon this, this is what I did:

less.renderSync = function (input, options) {
    if (!options || typeof options != "object") options = {};
    options.sync = true;
    var css;
    this.render(input, options, function (err, result) {
        if (err) throw err;
        css = result.css;
    });
    return css;
};

[jhnns]

Cool!

There is just one problem: It is very unusual to do something synchronously while accepting a callback (as the render-function does). You’re suggesting a sync-option like this:

less.render(
    input,
    { ... sync: true ... },
    function (err, result) {
    }
);

?

Imho it’s weird to have the callback being called synchronously. I’d expect an api like this:

// async
less.render(input, option, callback);

// sync
var result = less.renderSync(input, option);