- [x] Have you signed the [CLA](http://www.ubuntu.com/legal/contributors/)? ----- I was getting some PyRight errors when trying to create a `PartSpec` with just a `plugin` value: ```python3 foo = PartSpec(plugin="foo") ``` PyRight gives me this error: ``` error: Arguments missing for parameters "organize", "overlay", "stage", "prime" (reportCallIssue) ``` It could also be PyRight misinterpreting something, but using `default_value` instead of `default` for mutable types seems like a good idea anyway, and as a side effect seems to silence PyRight's error report. Conceptually, the `pydantic.Field`'s `default` vs `default_factory` have the same semantic as Python's own [`dataclasses.field`](https://docs.python.org/3/library/dataclasses.html#dataclasses.field) class, which says about `default_type`: > Among other purposes, this can be used to specify fields with mutable default values, as discussed below. Installed versions: - Python 3.11.6 - via pip: craft-cli 2.5.0 - via pip: craft-parts 1.20.0 - via pip: craft-providers 1.12.0 - via pip: pydantic 1.10.12 - via pip: pydantic_core 2.14.6 - via pip: pydantic-yaml 0.11.2 - via snap: pyright 1.1.348 746 latest/stable alexmurray* classic This might interact with #601. See also: https://github.com/canonical/craft-parts/pull/601/files#r1463405279