python / python/mypy

Data Class Transforms add `__dataclass_fields__`

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#15,974 10 comments 0 reactions 0 assignees View on GitHub

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topic-dataclass-transform topic-dataclasses
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Python
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Description

Per PEP 681, data class transforms are defined in terms of dataclasses, but it doesn't mean they make dataclasses.

In particular, transformed classes don't necessarily have __dataclass_fields__ or have is_dataclass return True, but per mypy - they do.

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reading PEP 681 and the existing handling of data class transforms in mypy, then compare mypy's behavior with runtime dataclasses for dataclass_fields and is_dataclass. Done means the type checker consistently reflects the intended PEP 681 semantics, with regression coverage for transformed classes.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
devtools
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
38/100

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