json_encoders not respected for enum.Enum in V2

[tobni]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

We are using json_encoders={enum.Enum: lambda val: val.name} in pydantic V1. In V2, this setting seems to be ignored when migrating to V2.

Example Code

import enum

import pydantic
from pydantic import ConfigDict


class MyEnum(enum.Enum):
    A = 'a'
    B = 'b'

class A(pydantic.BaseModel):
    a: MyEnum
    model_config = ConfigDict(json_encoders={enum.Enum: lambda val: val.name})


print(A(a = MyEnum.A).model_dump_json()) # {"a":"a"}, expected {"a":"A"}

Python, Pydantic & OS Version

pydantic version: 2.1.1
        pydantic-core version: 2.4.0
          pydantic-core build: profile=release pgo=true mimalloc=true
                 install path: .../lib/python3.10/site-packages/pydantic
               python version: 3.10.2 (main, Mar  3 2022, 12:03:29) [GCC 9.3.0]
                     platform: Linux-5.14.0-1054-oem-x86_64-with-glibc2.35
     optional deps. installed: ['typing-extensions']

Selected Assignee: @samuelcolvin

[samuelcolvin]

@adriangb please can you have a look at this since you worked on json_encoders.

[adriangb]

It's likely a bug stemming form the complexity in GenerateSchema. I think we can fix it, but it may not be trivial.