Update Dataclasses docs

[tpdorsey]

• document new dataclasses features
• review docstrings
• update typeadapter links

Change Summary

Related issue number

Closes PYD-54

Checklist

• Unit tests for the changes exist
• Tests pass on CI and coverage remains at 100%
• Documentation reflects the changes where applicable
• changes/<pull request or issue id>-<github username>.md file added describing change
  (see changes/README.md for details)
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

Selected Reviewer: @davidhewitt

[linear]

PYD-54 Review usage docs: usage/dataclasses.md

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View logs

[tpdorsey]

please review

[ybressler]

Thank you for going through the documentation! Your changes are scrupulous.

I left some comments + requested changes related to style + grammar. Overall, looks really good.

[tpdorsey]

please review

[ybressler]

Looks good! I have one small change about one word ;)

Also, one outstanding thread about how to resolve potential confusion with model_config for basemodels and config for dataclasses. Pending resolution, we should be good to go!

[ybressler]

Changes look great!

[tpdorsey]

Please review

[gordonhart]

Hi @tpdorsey! Could you help me understand what you meant by this diff? It looks to me like the current support for extra="allow" is the same as it was after #2557 (the PR where the removed copy was introduced), but I'm wondering if I'm missing something.

With extra="allow", extra values passed to __init__ still end up in the instantiated object, but just aren't surfaced via __str__. Example script:

from pydantic.dataclasses import dataclass

@dataclass(config=dict(extra="allow"))
class Example:
    ...

obj = Example(a=1, b=2)
print(obj)
print(f"Extra: a={obj.a}, b={obj.b}")

This script yields the following output when running with the latest pydantic==2.3.0:

Example()
Extra: a=1, b=2

[hramezani]

Hey, Could you please make an issue or ask this in a GitHub discussion?

[gordonhart]

Thanks for the quick response, @hramezani — opened #7362 to discuss.