[BUG][python-fastapi] fieldNames with reserved words are turned into private attributes in pydantic models

[andlien]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When generating pydantic models with the python-fastapi generator, reserved words are escaped by prepending an underscore. This results in pydantic treating the fields as a private attribute which is ignored in validation and (de)serialization. Furthermore, as of Pydantic v2.1.0, you receive a NameError if trying to use the Field function with a private attribute.

openapi-generator version

latest master

OpenAPI declaration file content or url

Sample OpenApi spec

Generating models for this spec results in the following model

class TestDTO(BaseModel):
    _self: StrictStr = Field(alias="self")
    foo: StrictStr
    bar: StrictStr
    __properties: ClassVar[List[str]] = ["self", "foo", "bar"]

Generation Details

No special config

Steps to reproduce

openapi-generator generate -i sample.json -g python-fastapi -o /tmp/test/

Related issues/PRs

I have not found anything related

Suggest a fix

The escaping is currently performed in AbstractPythonCodegen.escapeReservedWord(). The python client generator also generates pydantic models, but it's overriding the method prepending "var_" istead. I assume copying this implementation in PythonFastAPIServerCodegen.java would fix the issue.

[wing328]

thanks for reporting the issue

as a workaround, please use the name mapping option: https://github.com/openapitools/openapi-generator/blob/master/docs/customization.md#name-mapping