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Example Code

from pydantic import BaseModel, SecretStr
from fastapi.encoders import jsonable_encoder


class Credentials(BaseModel):
    password: SecretStr


ENCODERS = {SecretStr: lambda v: v.get_secret_value() if v is not None else None}

creds = Credentials(password="helloworld")

a = jsonable_encoder(creds)
print(a)  # {'password': '**********'}, as expected
b = jsonable_encoder(creds, custom_encoder=ENCODERS)
print(b)  # {'password': 'helloworld'}, as expected
c = jsonable_encoder(creds)
print(c)  # gives {'password': 'helloworld'}, but should be {'password': '**********'}?


creds = Credentials(password="123456789")

d = jsonable_encoder(creds)
print(d)  # gives {'password': '123456789'}, but should be {'password': '**********'}?

Description

• I'm using jsonable_encoder at multiple locations in the code, sometimes with custom_encoder and sometimes without.
• My understanding is that passing custom_encoder should only affect the current call and not modify any global state.
• What actually happens is that it modifies __config__.json_encoders, and as a result, public API endpoints might suddenly start returning secret values that should be filtered.

Operating System

Linux

Operating System Details

No response

FastAPI Version

0.78.0

Python Version

Python 3.9.2

Additional Context

Using Pydantic version 1.9.1.