AE Extendscript layered source file - adobe

Question

I'm working on a script that does find/replace for missing items in your project. Unfortunately I'm running into a situation detecting and then replacing layered image sources (psd, ai, etc.).
1) I see no way of detecting if a AvItem is a layer within a layered image other than parsing the item.name, which is unreliable because a user can always rename items in the project panel.
2) Once I do know that it is a part of a layered image I cannot figure out how to re-link it to the correct image without replacing the layer with the merged image. item.replace(new_path) will replace that item with the whole image, not the layer within the image. For example:
var item = app.project.item(3); //assuming this is the 'layer' we want to replace
item.replace(new_path);
So is there a secret property somewhere which will reliably tell me if an item is a part of a layered image, and if so is there a way to relink it without replacing the layer with the entire merged image?
EDIT
Here's a function to guess if a layer is part of a layered image. It's not bullet-proof but it should work as long as the user does not rename the item:
function isSourceLayered (av_item) {
// check if there is a "/"
if (av_item.name.indexOf("/") != -1) {
// check if it is in a "layers" folder
if (av_item.parentFolder.name.indexOf("Layers") != -1) {
return true;
}
}
return false;
}

Answer 1

I just asked the same question on the Adobe extendscript forum. Unless there's undocumented features (and I spent a bit of time looking with Extendscript Toolkit's data browser) the fileSource object doesn't seem to have any attributes or methods to do this.
There is a kind of a workaround, you can import the file using ImportOptions.importAs(ImportAsType.COMP) This will import a comp, and you can loop through the layers matching the name, get the source of that layer and use that as your new source. But as you say, it doesn't work if the source has been renamed.
I've written this into a function, it's available on github Edit: I forgot that I changed the way that function works. It doesn't re-import layer sources because of this problem, it just uses the Duplicate menu command.