python / python/typing

Allow `issubclass` for protocols with class variables

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#822 8 comments 0 reactions 0 assignees View on GitHub

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topic: feature
Dominant language
Python
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Merged PRs (30d)
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Description

Currently issubclass cannot be used for runtime_checkable protocols with data members, because those attributes could be set in __init__. I propose to relax this restriction to allow protocols with ClassVar members, as those should be present in the class definition.

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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 tracing the repository's handling of runtime_checkable protocols, data members, and issubclass checks. Determine how ClassVar members are represented and validated, then update the relevant behavior and tests so ClassVar protocols are accepted while protocols with instance data members retain the existing restriction.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
tooling
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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