Cannot parse a list of dataclasses with optional dataclass member

[mnidza]

🐛 Bug report

I am getting an when parsing a list of dataclass objects, where the dataclass has an optional member which is another dataclass.

To reproduce

In script.py

from dataclasses import dataclass
from typing import Optional
from jsonargparse import CLI

@dataclass
class A:
    x: int

@dataclass
class B:
    a: Optional[A] = None

def f(b: list[B]):
    print(b)

CLI(f, as_positional=False)

In config.yaml

b:
  - a:
      x: 1

In terminal

script.py --config config.yaml

Expected behavior

Expected console output

[B(a=A(x=1))]

Actual console output

usage: script.py [-h] [--config CONFIG] [--print_config[=flags]] --b B
error: Validation failed: No action for key "a.x" to set its default.

Environment

• jsonargparse version: 4.29.0
• Python version: 3.11.4
• How jsonargparse was installed: pip install jsonargparse[signatures]
• OS: Windows 11 Enterprise, 10.0.22631

[mauvilsa]

Thank you for reporting! This is fixed with #527.