feat: add PEP 695 type alias support and improve type handling

[Rub1kCube]

Summary

This PR adds full support for type aliases from PEP 695 (Python 3.12+) and improves overall type handling in polyfactory.

Key Changes

1. normalize_type function

Added a new normalize_type function that serves as a compatibility layer for handling different type representations across Python versions. This adapter:

• Problem it solves: PEP 695 introduces TypeAliasType, which requires special handling to extract the underlying type value. Polyfactory couldn't process this new type during data generation, which led to errors:

polyfactory.exceptions.ParameterException: Unsupported type: ExampleTypeAliasType on field 'example_field' from class FooFactory.
Either use 'add_provider', extend the providers map, or add a factory function for the field on the model.

The adapter also correctly handles nested scenarios such as list[ExampleTypeAliasType], resolves generic TypeAliasType, and cases where other TypeAliasType instances are used as generic type parameters.

Additionally, I've refactored type checking logic by introducing two utility methods:

• is_generic_alias(): Checks if a type is a generic alias
• is_type_var(): Checks if a type is a TypeVar

All instances of isinstance(value, TypeVar) have been replaced with is_type_var(value) for consistency. Comprehensive tests have been added to ensure the adapter works correctly with various type scenarios.

2. Rationale for the Chosen Approach

The type normalization in PydanticFieldMeta.from_field_info is implemented as:

field_info = FieldInfo.merge_field_infos(
    field_info, 
    FieldInfo.from_annotation(normalize_type(field_info.annotation))
)

This approach provides several benefits:

• Clean implementation: Using normalization without conditional checks like is_type_alias improves code readability and eliminates the need for redundant tests that verify conditional behavior for each type scenario
• Metadata preservation: Using merge_field_infos ensures that metadata like example values aren't lost during the annotation transformation

Testing

• Added extensive test coverage for PEP 695 type aliases including:
  • Basic type aliases
  • Generic type aliases with single and multiple type parameters
  • Nested generic structures
  • Annotated types with constraints
  • Union types and optional types
  • Complex nested combinations
• Added tests for the normalize_type function
• Added tests have been written to check support PEP 695 for DataclassFactory

Fixes #707

[adhtruong]

Thanks for the work on this! Change looks good. Can conflit be resolved?

[Rub1kCube]

Conflict has been fixed 👍

[adhtruong]

Apologies - realised created another conflict for here when merging other things. Can this be updated again please?

[Rub1kCube]

Apologies - realised created another conflict for here when merging other things. Can this be updated again please?

Conflict has been fixed

[github-actions]

Documentation preview will be available shortly at https://litestar-org.github.io/polyfactory-docs-preview/711

[adhtruong]

https://github.com/all-contributors add @Rub1kCube for code

Thanks for the work on this!