litestar-org/polyfactory

Enhancement: Support non-mutable Mapping containers

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#726 opened on Jul 3, 2025

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enhancementgood first issue

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Description

Summary

Currently handle_collection_type only supports MutableMappings, could support for non-mutable Mappings also be added? I am personally trying to use this alongside the frozendict pypi package.

Basic Example

You could make a factory for e.g.

@dataclass
class Shop(frozen=True)
    prices: MyImmutableMapping[str, int]

where MyImmutableMapping is a subclass of Mapping. Currently this will raise

 NotImplementedError: Unsupported container type: <class 'MyImmutableMapping'>

Drawbacks and Impact

Very few drawbacks in my opinion: changes should be small and isolated and adds functionality many users could benefit from.

Unresolved questions

No response

Contributor guide

Research direction
Examine the `handle collection type` function in `polyfactory/value generators/complex types.py` and extend it to support non mutable `Mapping` types by checking if the type is a subclass of `collections.abc.Mapping` and generating appropriate data.
Tech stack
python
Domain
backend
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Pythoncollections.abc
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75