Overwriting subconfig retains values from default subconfig

[cristianregep]

🐛 Bug report

I have a master config that is formed from multiple other sub-configs stored in separate files (one for data, one for architecture etc.). When I specify from the CLI a different version of a sub-config my expectation is that the sub-config gets completely overwritten. Instead, what I got is a merged sub-config between the default and the one provided through the CLI. I believe this is a bug. Otherwise let me know if this intended, and if maybe there is a setting through which we can control the behaviour to overwrite

To reproduce

test.py

from jsonargparse import CLI
from dataclasses import dataclass


@dataclass
class Data:
    attribute_1: int
    attribute_2: int


@dataclass
class Test:
    data: Data


print(CLI(Test, fail_untyped=True))

main_config.yaml

data: data_default.yaml

data_default.yaml

attribute_1: 1
attribute_2: 10

data_new.yaml

attribute_1: 2

python test.py --config main_config.yaml --data data_new.yaml

Expected behavior

I should get an error that says attribute_2 is required but has not been provided.

Instead, i get Test(data=Data(attribute_1=2, attribute_2=10))

Environment

• jsonargparse version: 4.23.1
• Python version : 3.10.12
• How jsonargparse was installed: pip install jsonargparse[signatures,typing-extensions]==4.23.1
• OS (e.g., Linux): Ubuntu 22.04.2 LTS