Traverse Bodies for Join Feature. Inconsistent results.

[Le_Bear]

I guess I have been looking at this for too long, I don't see problems clearly anymore.
The goal is to create a SINGLE body out of a multi components assembly which can be complex. It "seems" that it works, if there are not too many components, if the ROOT is selected.  BUT, I would like this to work also if I select a component, not always the root, as some assemblies are too big/complex to always start from the root.

Here is the code so far :

from typing import NewType
import adsk.core, adsk.fusion, traceback


lst = [] #body list

def traverse(occurences, bodies):
    # recursive method to get all bodies from components and sub-components
    for occ in occurences:    
        for bod in occ.bRepBodies:

            if (bod.isVisible):
                lst.append(bod)

        if occ.childOccurrences:
            traverse(occ.childOccurrences,bodies)
    
def run(context):
    ui = None
    try:
        app = adsk.core.Application.get()
        ui  = app.userInterface
        

        # Get active design
        product = app.activeProduct
        design = adsk.fusion.Design.cast(product)
        if not design:
            ui.messageBox('It is not supported in current workspace, please change to MODEL workspace and try again.')
            return

        # History must be captured for this to work
        if design.designType == adsk.fusion.DesignTypes.DirectDesignType:
            design.designType = adsk.fusion.DesignTypes.ParametricDesignType

 
        # Get root component in this design
        rootComp = design.rootComponent
        selectedComp = design.activeComponent
               
        # Get all Components below root       
        occs = selectedComp.occurrences
        r_occs = rootComp.occurrences

        bodies = selectedComp.bRepBodies

        # add all bodies from all components in the collection 
        traverse(occs, bodies)

        ui.messageBox('Num bodies: ' + str(len(bodies)))

        # create the new component , adding "for STL Export" to the name       
        newComp = r_occs.addNewComponent(adsk.core.Matrix3D.create())                
        newComp.component.name = selectedComp.name + " - ONE BODY"

        #num = len(lst) // STEP
        
        cpyBodies = newComp.component.features.copyPasteBodies
        sourceBodies = adsk.core.ObjectCollection.create()

        # modif pour tacher d'agglutiner tout ça, même si on voit tout. On verrra après pour base feature, si possible.

        sourceBodies.add(lst[000])
        cpyBodies.add(sourceBodies)
       
        #adsk.doEvents()
        
        sourceBodies.clear()
        for bod in lst:
            adsk.doEvents()
            sourceBodies.add(bod)
            #cpyBodies.add(sourceBodies)

        



        firstBody = newComp.component.bRepBodies.item(0)        
        #firstBody.name = newComp.name

        combines = rootComp.features.combineFeatures
        combine_input = combines.createInput(firstBody,sourceBodies)
        combine_input.operation = adsk.fusion.FeatureOperations.JoinFeatureOperation
        combine_input.isKeepToolBodies = False 
        combine_input.isNewComponent = False  
        returnValue = combines.add(combine_input)
        adsk.doEvents()
        returnValue.timelineObject.rollTo(True)  #nécessaire, sinon erreur
        firstBody = returnValue
        
        returnValue.timelineObject.rollTo(False)  #nécessaire, sinon erreur

On the F3D example sent, if I select (activate) "Flanc Gauche:1" component instead of the root, I get this error, which I really don't understand, as I don't get the path problem with bod.isVisible

I am sure this is "buggy", but as I said, I end up not "seeing" properly anymore. Also, I would like to learn how to do this using a base Feature, which seems to be a better way.