Fix error with empty dataclass inheritance

[dolfinus]

Fix @pydantic.dataclasses.dataclass() syntax failure on inheriting dataclass without changing fields list.

Closes #4565

[samuelcolvin]

@PrettyWood could you take a look at this?

[PrettyWood]

Does it fix all new tests related to dataclasses or just one?

[samuelcolvin]

No idea yet, @dolfinus please can you update the issue description to auto-close related issues.

Also, can you check if this fixes any other issues from #4552.

[samuelcolvin]

Also @dolfinus please include a descriptive PR title and don't include issue ids in titles.

[dolfinus]

This PR fixes only #4565. Other issues from #4552 are still present

[dolfinus]

Failing test for FastAPI is not linked to this PR, the same check is failing on 1.10x-fixes branch

[dolfinus]

Any updates?

[samuelcolvin]

This seems fine to me, @PrettyWood are you happy to accept this?

[samuelcolvin]

This affects the same line discussed on #4498, but doesn't appear to fix the problem.

@PrettyWood do you have any idea if there's an easy way to fix both #4498 and #4565?

[dolfinus]

This PR fixes only #4565. It does not fix the #4498, I've never mentioned that

[samuelcolvin]

I've never mentioned that

I understand that, but the line changed here is the same line discussed in #4498.

Obviously before we release v1.10.3, we need to fix both issues. Hence I'm trying work out a fix that covers both.

[PrettyWood]

I finally made a fix that fixes the related issue + 3 more. I'm sorry @dolfinus but this PR should probably be closed.
I know I took a very long time to make a bug fix but I had way too much on my plate and needed to wait for the holidays to arrive

[dolfinus]

Ok, thanks!