Replacing subPathItems in a vector mask

Question

It seems one can fairly easily replace a Layer’s Vector Mask with another one’s, but I fail to see if I can simply replace the Vector Mask’s subPathItems with a new array.
A pathItem’s subPathItems being read only this seems improbable, but still …
And on a related note: Do any of you know if one can create a Vector Mask without first creating a pathItem proper?
Because currently I have the Scripts create Paths, create Solid Color Layers with the Paths selected and then delete the Paths again, which seems to be a longish route.
Thanks for any input.

Answer 1

You can create a empty vector mask with a script.
    var desc13 = new ActionDescriptor();
        var ref10 = new ActionReference();
        ref10.putClass( charIDToTypeID('Path') );
    desc13.putReference( charIDToTypeID('null'), ref10 );
        var ref11 = new ActionReference();
        ref11.putEnumerated( charIDToTypeID('Path'), charIDToTypeID('Path'), stringIDToTypeID('vectorMask') );
    desc13.putReference( charIDToTypeID('At  '), ref11 );
    desc13.putEnumerated( charIDToTypeID('Usng'), stringIDToTypeID('vectorMaskEnabled'), charIDToTypeID('RvlA') );
    executeAction( charIDToTypeID('Mk  '), desc13, DialogModes.NO );
But as you pointed out pathItems are read only so it doesn't do much good unless you want the script to create a blank vector mask for the user to edit after the script is done.
Because you can't edit an existing path, the way you are creating vector masks is the only way I know. New path, mask from path, remove path.
The only way I know to 'edit' an existing path with scripting is to read the existing path converting into SubPathInfo and PathPointInfo which can be edited. Then delete the old path and create a new one from the edited data.
For a vector mask you add the extra steps. i.e. you read/convert the vector mask's path data, delete the mask, create a new path with the edited points, make a mask from that new path, then delete the new path.