empty_altair.py

def is_empty_chart(ch):
    spec = ch.to_dict()
    # Unit chart: no data, no mark, no encoding
    if "layer" not in spec:
        return not (spec.get("data") or spec.get("mark") or spec.get("encoding"))
    # LayerChart: check each sub-layer recursively
    # Check if the layer list is empty or all sub-layers are empty
    if not spec["layer"]:
        return True
    # For each sub-layer, check if it's empty by examining its dict directly
    # instead of converting back to Chart object (which can cause validation errors)
    return all(
        not (sub.get("data") or sub.get("mark") or sub.get("encoding"))
        for sub in spec["layer"]
    )