Bug: Grouping shapes fails in JavaScript for Automation

[draft8]

In AppleScript we can group some selected shapes by writing and running:

tell application "OmniGraffle"
    tell front window
        set selection to {assemble selection}
    end tell
end tell

(The selection method of the front window returns a list/array of graphics, and this is also the type expected as first argument by the assemble method of the application)

In JavaScript for Applications, .assemble() is found as a method of the OmniGraffle Application object, but fails silently when called on an array of graphics. It returns a null value, and has no effect, producing not even an error message.

var og = Application("OmniGraffle"),
    w = og.windows[0];

w.selection = [og.assemble(
    w.selection()
)];

[draft8]

An update:

It looks like some kind of type error. In Applescript, assemble succeeds with both:

1. A list of graphics (such as the return value of the selection method - see snippet above)
2. A reference, such as graphics of canvas of front window

tell application "OmniGraffle"
	tell front window
		set selection to {assemble graphics of its canvas}
	end tell
end tell

In the case of JavaScript for Automation, however, while the command succeeds with references, e.g. (all the graphics on the canvas:

var og = Application("OmniGraffle"),
    w = og.windows[0];

w.selection = [og.assemble(
    w.canvas.graphics
)];

It fails (though without any error message) with arrays.

i.e. we can group a logically defined set of shapes (using the ObjectSpecifier() syntax, but this is a rather marginal case. The core case will always be an array of specific shapes, such as the selection array.

[draft8]

and we can circumvent the type error in the scripting library by writing an elaborate kludge to convert the type of an array of shapes to a reference to a set of shapes that have the same ids as the elements of the array …

Sort of works (slowly), but offloads a noticeable burden onto the scripting customer :-)

(The hackRef() function which is needed is longer than the original code …

    // OG_graphics_collection -> [ og_graphic ] -> OG_graphics_collection
    function hackRef(graphics, lstGraphics) {
        var lng = lstGraphics.length;

        if (lng) {
            return graphics.whose(lng > 1 ? {
                _or: lstGraphics.map(function (g) {
                    return {
                        _match: [ObjectSpecifier().id, g.id()]
                    }
                })
            } : {
                id: lstGraphics[0].id()
            });
        } else return null;
    }

var og = Application("OmniGraffle"),
    w = og.windows[0];

w.selection = [og.assemble(
    hackRef(w.canvas.graphics, w.selection())
)];