tango.pyaml.attribute.Attribute missing from accelerator.schema.json

[GamelinAl]

Summary

The published schemas/accelerator.schema.json has no branch for tango.pyaml.attribute.Attribute, the writable Tango attribute used by every setpoint of a static catalog. A configuration using it fails schema validation with "is not valid under any of the given schemas", although pyAML loads it fine.

Cause

SchemaGenerator (pyaml/validation/generator.py, model_schema, ~lines 210-239) replaces the schema of any class that has registered subclasses by a oneOf union of its subclasses only:

if not subclasses:
    return base_schema
subschemas = [self.generate_inner(item.__pydantic_core_schema__) for item in subclasses]
merged = {"oneOf": subschemas}          # base class itself is dropped

AttributeReadOnly subclasses Attribute, so Attribute is dropped from the union. The same happens to any concrete class that is also subclassed.

Reproduction

import json
s = json.load(open("schemas/accelerator.schema.json"))
consts = set()
def walk(o):
    if isinstance(o, dict):
        if "const" in o: consts.add(o["const"])
        for v in o.values(): walk(v)
    elif isinstance(o, list):
        for v in o: walk(v)
walk(s)
print("tango.pyaml.attribute.Attribute" in consts)                    # False
print("tango.pyaml.attribute_read_only.AttributeReadOnly" in consts)  # True

Expected

A concrete class that has subclasses should be kept in the union alongside its subclasses (i.e. oneOf: [base_schema, *subschemas] when the base class is itself instantiable/registered).