Optional side nav

[mrchief]

Some of my pages have a side nav (not all, just a few). I'm using bootstrap and I was wondering how I could add proper classes when the sidenav file is present.

So when sidenav is present:

---col-3--- | ---col-9---
sideNav     | page content

when not:

---col-12---
page content

My first shot was to do something in layout.jade but I cannot figure out how to check if the sideNav file is present or not in a simple way.

Here's roughly what I'd like to do in _layout.jade:

div.content-wrapper
    if(current folder has a _sideNav.jade)
        .sidebar-wrapper
            != partial(current.path.join('/') + '/_sideNav')

        article.main-container
            != yield
    else
        article.main-container
            != yield

Is this doable? Or is there a better way to handle this?