How to reference an external schema for a model

[booooh]

First Check

• I added a very descriptive title to this issue.
• I used the GitHub search to find a similar issue and didn't find it.
• I searched the FastAPI documentation, with the integrated search.
• I already searched in Google "How to X in FastAPI" and didn't find any information.
• I already read and followed all the tutorial in the docs and didn't find an answer.
• I already checked if it is not related to FastAPI but to Pydantic.
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Example Code

class Foo(BaseModel):
    pass

Description

I'm looking for a way to override the '$ref' field of a model so that I can reference an external schema. The schema is hosted on a different server, as the model is shared between multiple micro-services.

I have a pydantic model say Foo and I'd like to reference an external schema:

class Foo(BaseModel):
    pass

And I would like it to reference the schema at https://example.com/api/v1/openapi.json#/components/schemas/Foo
Is there a way to customize the openapi documentation reference that URL instead of the local one?

Operating System

Linux

Operating System Details

No response

FastAPI Version

0.73

Python Version

3.6.13

Additional Context

No response

[booooh]

Answering myself:

1. It is a pydantic thing after all
2. You can override a pydantic Model's schema using the schema_extra property Config class for the Model:

class Foo(BaseModel):

    class Config:
        def schema_extra(s):
            s.clear()
            s["$ref"] = "https://example.com/api/v1/openapi.json#/components/schemas/Foo"

[afandian]

Thanks for coming back to give the answer! I found this useful: https://stackoverflow.com/questions/71035845/example-in-schema-extra-is-ignored-by-pydantic-in-fastapi , especially the json_schema_extra comment.