How to correctly add a PANTONE swatch in Illustrator with Extendscript?

Hello,

I'm working on a script to generate several files in a printing process:

- a file which contains a single item of the imposition

- a file which contains the proof of the item (to send to customer)

- a file which contains the imposition of items to print

To automate a maximum the different actions of the process, I would like to add all the colors which are used on the printing item in the swatches of each generated files. I can have orders only in CMYK, or in CMYK plus 1, 2, or 3 PANTONE colors.

There is no problem for me to add CMYK colors or custom colors built from CMYK tints in document swatches, but I don't know how I can add a PANTONE color in swatches. In fact, I generate blank files with all "parameters" I need to work correctly, and when all files are generated, I work only on the single item file (single item file which is imported by my script into the imposition file and the proof file).

So my question is the following : to add a PANTONE color in swatches, is it better to "generate" it with CMYK colors (and add it in swatches like a ColorModel.SPOT) or is it possible (and probably better) to add it from the PANTONE library?

For example I add my custom spot colors with this function:

function addSpot(name,c,m,y,k){  
    try {    
        swatch = app.activeDocument.swatches[name];   
        addSpot (name+='1', c, m, y, k);  
    }    
    catch (e) {    
        var newSpot = app.activeDocument.spots.add();    
        newSpot.name = name;    
           
        var newColor = new CMYKColor();    
        newColor.cyan = c;    
        newColor.magenta = m;    
        newColor.yellow = y;    
        newColor.black = k;    
    
        newSpot.colorType = ColorModel.SPOT;    
        newSpot.color = newColor;    
        var newSpotColor = new SpotColor();    
        newSpotColor.spot = newSpot;    
    }    
}

What's the best way to add a PANTONE color in document swatches, even if the document have no element?

Thanks a lot in advance for your replies

Jo